A/C doesn't go on at all

I recently noticed that my car A/C was not blowing cold AT ALL. I checked under the hood and noticed that I didn't even get a "click" when someone turned the A/C on. Like a dweeb, I went out and paid $28 bucks for a replacement A/C Cutoff Switch (the round thing that gets seated in the oil in the compressor). I didn't first check the power to the switch like I should have (doh!). There is no power going through the wires to the switch and just a few microvolts of change on the meter when I turn the A/C on and off. So, no power to the compressor = no A/C. The problem is, I can't figure out where the damn wires go and there is no obvious fuse or relay that controls the power to the compressor.

I'd appreciate it if you could tell me:

How much power should be going to the compressor?
Where the power source is for the two wires (I think one is dark blue and the other light blue)?
What fuse/relay controls the power to that switch?
What are the next steps in repairing this issue?

I checked every fuse in the fusebox in the side of the dash and they are all good.

HELP!

John

First off, would help to know what year we are dealing with.....

Maybe, you have a freon leak and you have no pressure or low pressure in the system....checked with gages?

Look at your accumulator....does it have an external switch mounted on it?

If yes, disconnect it(pressure cycling switch).....with key on(not running), jumper the two wire connector....does the compressor clutch now click and engage? If it does, it's one of two things....either your system pressure is too low, or the switch is bad.....

Sorry, it's a 93 caprice classic V8 5.0.

The accumulator has a 2 prong connector that plugs into it.. Just to make sure I have it right, you want me to disconnect the connector on the accumulator, short the prongs and then test out the compressor with the engine power on but not running?

Sorry, it's a 93 caprice classic V8 5.0.

The accumulator has a 2 prong connector that plugs into it.. Just to make sure I have it right, you want me to disconnect the connector on the accumulator, short the prongs and then test out the compressor with the engine power on but not running?

If you remove that two wire connector, and insert a jumper or shunt into the plug (key on engine off) and hear the clutch on the compressor kick in, then the switch is the issue and should be replaced. Short the terminals in the plug, not the terminals on the switch.

If the switch is bad, it is easily replaced. It screws on to a fitting that has a Schrader valve (like the connection ports).

If you remove that two wire connector, and insert a jumper or shunt into the plug (key on engine off) and hear the clutch on the compressor kick in, then the switch is the issue and should be replaced. Short the terminals in the plug, not the terminals on the switch.

If the switch is bad, it is easily replaced. It screws on to a fitting that has a Schrader valve (like the connection ports).

I'm so sorry...I'm being a bit thick today....

So I pull the plug out of the evaporator (the switch is mounted on the evaporator I assume) and then shunt the plug, correct?

If I do that and the clutch kicks on, does it mean that I have a bad switch on the compressor, that I am low on refrigerant or could it be either? If that test doesn't confirm that I am low on refrigerant, how would I diagnose that condition?

Thanks for your patience!

If you remove that two wire connector, and insert a jumper or shunt into the plug (key on engine off) and hear the clutch on the compressor kick in, then the switch is the issue and should be replaced. Short the terminals in the plug, not the terminals on the switch.

If the switch is bad, it is easily replaced. It screws on to a fitting that has a Schrader valve (like the connection ports).

Ok, I shorted the plug as you suggested and heard a click. Not from the compressor, but from on of the square relays on the passenger side near the firewall. What is this telling me?

Ok, I shorted the plug as you suggested and heard a click. Not from the compressor, but from on of the square relays on the passenger side near the firewall. What is this telling me?


the low pressure cut out switch connector you shorted out then a relay clicked ...I would check for pressure at the low side refrigerant port. with the engine off the pressure should be around 120 psi. If you have pressure over 20 psi this switch should short together and pass the power to the relay then compressor. using an ohm meter you could measure the switch resistance to see if it is open with pressure. if so the switch is no good. you simply un screw and replace it .

I would check the fuse , compressor fuse for being open .


with the engine on ,,,, ac on the pressure should drop to 40 psi APPROX WITH THE COMPRESSOR WORKING. which is not happening for you now..

the low pressure cut out switch connector you shorted out then a relay clicked ...I would check for pressure at the low side refrigerant port. with the engine off the pressure should be around 120 psi. If you have pressure over 20 psi this switch should short together and pass the power to the relay then compressor. using an ohm meter you could measure the switch resistance to see if it is open with pressure. if so the switch is no good. you simply un screw and replace it .

I would check the fuse , compressor fuse for being open .


with the engine on ,,,, ac on the pressure should drop to 40 psi APPROX WITH THE COMPRESSOR WORKING. which is not happening for you now..

Where is the best source for me to get R-12 and what equipment do I need to measure the pressure and install the refrigerant? I am a 609 Certified Tech, so I can buy it legally. But it seems nearly impossible to find in Philadelphia.

Where is the best source for me to get R-12 and what equipment do I need to measure the pressure and install the refrigerant? I am a 609 Certified Tech, so I can buy it legally. But it seems nearly impossible to find in Philadelphia.

not sure on the R12 refrigerant . I have a case of 12 oz cans here. I would not sell to anyone with out proper license . also I would never ship this stuff. If you need to convert , this is costly to do properly ...call in your area for a direct drop in substitute refrigerant . I was reading a while back about this. could be only available in some other country than the USA..

when adding you measure the low and high side pressures. then using the pressure chart for your vehicle with the outside air temp you can determine the correct refrigerant amount. on my 1996 impala with R134 80deg f air temp I expect 40-45 psi low side with 275 psi on the high side.

what happens if you put too much in is the high side will rapidly rise into the 300psi plus range , you will see as you add the high side slowly rise when it starts to rise at a faster rate then its a little too much....using the chart for your vehicle is very good rather than dump out the charge. then refill with the correct amount. also to do this you would need a recovery machine to protect from releasing the R12.

not sure on the R12 refrigerant . I have a case of 12 oz cans here. I would not sell to anyone with out proper license . also I would never ship this stuff. If you need to convert , this is costly to do properly ...call in your area for a direct drop in substitute refrigerant . I was reading a while back about this. could be only available in some other country than the USA..

when adding you measure the low and high side pressures. then using the pressure chart for your vehicle with the outside air temp you can determine the correct refrigerant amount. on my 1996 impala with R134 80deg f air temp I expect 40-45 psi low side with 275 psi on the high side.

what happens if you put too much in is the high side will rapidly rise into the 300psi plus range , you will see as you add the high side slowly rise when it starts to rise at a faster rate then its a little too much....using the chart for your vehicle is very good rather than dump out the charge. then refill with the correct amount. also to do this you would need a recovery machine to protect from releasing the R12.

I understand the regulations regarding R-12 and if you would be willing to part with the amount I need, I do have the proper EPA 609 certification (which I could email you) to purchase and use R-12, R-22 and a number of other refrigerants. Shipping of this is done all the time but must be sent ground (most people use UPS). If you would be willing to sell some to me, I'd really appreciate it and please PM so we can discuss it further.

When I go to the pomona swap meet here in socal, I can usually find someone selling R12 for about $15 for a 14oz can. I try to have a few cans on hand since my caprice still uses R12.

If you look on ebay, there are currently listings for people selling R12 in the small cans and also 30LB cylinders. If you go to a shop here, they charge a small fortune to charge your system with R12 if you can find a shop that still uses it.
That stuff is getting scarce, I think because jcAT is hoarding it all.. :)

R-12 is expensive......if you put it in without finding the leak, you might as well just give me the money.....I promise to enjoy it.....

Actually, a conversion is not that expensive.......

I get a vacuum of 21 psi on the low side with compressor on and jus above 0 psi with compressor off. What does this mean?

Your system is empty.....with a possibly blocked orifice tube....

How did you get the compressor to run?

Your system is empty.....with a possibly blocked orifice tube....

How did you get the compressor to run?

Took off the plug to the evaporator and shorted it for testing purposes. I checked the hoses and ports carefully and there doesn't seem to be an oil leak. Where should I go from here? Bought the car for $1,000, so I'm not going to spend that much having a mechanic fix the A/C. What are my options?

If you don't want to put money into the vehicle, then do nothing, but you won't have A/C....

As already stated, most shops don't even deal with R-12 systems......I remember our last tank of R-12.......we paid something like 4X's the normal rate.....we repaired a vehicle.....used maybe 2#'s....about a week later I go to use it again, and I notice the tank is light.......the valve was shut off, but when soap tested, could see an external leak at the valve.....lost almost all of it.....owner was pissed, and we only did conversions after that....

You need to find the leak to do a repair, or it just will leak out again.....

If you have any kind of A/C experience, basically all you need is a conversion kit, and a vacuum pump, and a set of gages.....if you don't have experience, then have it done at a local A/C shop.....

If you don't want to put money into the vehicle, then do nothing, but you won't have A/C....

As already stated, most shops don't even deal with R-12 systems......I remember our last tank of R-12.......we paid something like 4X's the normal rate.....we repaired a vehicle.....used maybe 2#'s....about a week later I go to use it again, and I notice the tank is light.......the valve was shut off, but when soap tested, could see an external leak at the valve.....lost almost all of it.....owner was pissed, and we only did conversions after that....

You need to find the leak to do a repair, or it just will leak out again.....

If you have any kind of A/C experience, basically all you need is a conversion kit, and a vacuum pump, and a set of gages.....if you don't have experience, then have it done at a local A/C shop.....

What is the best way to find a leak - without charging up the system with, as you point out, expensive freon?

There is only one best way.....add freon and a dye, run compressor and then using a black light you look for a visible leak......in some cases, the leak may be so small it takes awhile for the oil to leak out.....also, there are parts of the system that you can't see, like a pipe covered by insulation or the evaporator that is buried in the air duct work......for that a refrigerant "sniffer" is invaluable.....there are times when the leak is so small, that you may have to run the system, for a week, to find a trace of the leak....

If you are lucky, it's a huge leak, and easily found....

There is only one best way.....add freon and a dye, run compressor and then using a black light you look for a visible leak......in some cases, the leak may be so small it takes awhile for the oil to leak out.....also, there are parts of the system that you can't see, like a pipe covered by insulation or the evaporator that is buried in the air duct work......for that a refrigerant "sniffer" is invaluable.....there are times when the leak is so small, that you may have to run the system, for a week, to find a trace of the leak....

If you are lucky, it's a huge leak, and easily found....

First of all, if I forgot to thank you for all of the help you provided. I really appreciate it.

I was able to test both sides of the line. The system is COMPLETELY out of freon. I guess there are two ways I can go from here:

1) Do a partial fill with dye and expensive R-12 and hope the leak is not in any place too nasty. I assume that since ALL the freon has left the building, it isn't a small leak.

2) Convert the system to R-134a. I understand that the cooling power of this mix is not as good as R-12, but the stuff is considerably less expensive. If I decided to go this route, what do you think about the conversion kits and the process? There are so many opinions on this that it is hard to know who to believe. I noticed that the "standard" conversion kit will not work on my car because it comes with the wrong high-side fitting, so I will have to get a different one. And what about the oil in the compressor? Do I have to suction that all out or can I use the existing oil? Do I need to change out any other parts or am I good with what I have? Also, where is the orifice tube? Might as well change that out with the system depressurized. These Haynes books suck.

J

If you do the conversion, replace the accumulator and flush out the system using a product for the occasion. Once the system is flushed, fully evacuate the system and then using ESTER oil, add the proper amount and then the proper amount of R134a.

On my 1988, the system holds about 2.5 cans of R134a. Note this is less than the R12 charge, due to the higher head pressure of R134a.

If you do the conversion, replace the accumulator and flush out the system using a product for the occasion. Once the system is flushed, fully evacuate the system and then using ESTER oil, add the proper amount and then the proper amount of R134a.

On my 1988, the system holds about 2.5 cans of R134a. Note this is less than the R12 charge, due to the higher head pressure of R134a.

So would it be your recommendation to do the conversion, based on your experience, or to stay with the R-12? And since the system is completely depressurized, would I just suction the oil out of the compressor?

So would it be your recommendation to do the conversion, based on your experience, or to stay with the R-12? And since the system is completely depressurized, would I just suction the oil out of the compressor?

The R134a is not bad, if you could get a larger evaporator (in terms of area) it would work better, but it's OK - and I use it in my car here in the Phoenix, AZ area.

You would need to run a flushing agent through the system to get as much oil residue out as you can, and when you do refill the system, do NOT use PAG oil - use Ester. PAG will result in the demise of your compressor.

This is what I used to flush my system last year when I replaced the compressor - linky (http://www.oreillyauto.com/site/c/detail/INT0/CA1/N1785.oap?ck=Search_N1785_-1_-1&pt=N1785&ppt=C0050). It would be wise to replace the orifice tube as well, it's inexpensive and a plugged orifice tube can ruin your day when you're trying to get the system working.

Silicon212, why the ester oil instead of the Pag? GM recommends the Pag......

Also it's recommended that the mineral oil be removed(and measured) from the compressor, and replaced with Pag......and then enough Pag oil should be added to the system.....typically 8 oz., total.....the rest of the mineral oil that is within the system, is compatible with the Pag.......like you say, the accumulator(with new desiccant) should be replaced......naturally, it would be better if the system was flushed of as much mineral oil as possible....but you will never get rid of all of it from the evaporator and condenser......

DO NOT USE CHEAP RETRO KITS! The valves will leak..........

formula for 134a is: multiply recommended r12 weight by 0.9......then from that, subtract 0.25 for the weight of r134a.......

for example......if the capacity of your r12 system is 2.0 pounds, 2 X 0.9= 1.8......then subtract 0.25 from that and you get, 1.55 pounds of 134a.....

The reason for this is to decrease head pressures.....but who has a sensitive enough scale for this? Only the expensive a/c machines do....

I would, personally, fill by pressure, using the appropriate graph of ambient temp and humidity.....

Unfortunately, most people don't have vac pumps to pull a vacuum on a system to do this job....I personally would let a shop do it......shop around....

PAG is absolutely incompatible with the R12 oil, and any trace of the oil used in an R12 system will cause damage to the system. Ester is compatible with both R12 and R134a systems, that's why the recommendation. PAG is only for use in systems that are R134a from the very start.

Well, I have to disagree that:

"PAG is absolutely incompatible with the R12 oil"

Especially in GM systems.....GM calls for Pag in their retrofit bulletins...

Well, I have to disagree that:

"PAG is absolutely incompatible with the R12 oil"

Especially in GM systems.....GM calls for Pag in their retrofit bulletins...

I have to say that PAG oil / PAG 150 is for GM AC systems that NEVER HAD ANY MINERAL OIL IN THEM .

when converting an R12 system to R134 you use a conversion oil. ester oil is the correct oil. this chemically is compatible with the mineral oil. even with cleaning agents you will have some MINERAL oil trapped in the system. The use of PAG in this R12 system would result in what some call the BLACK DEATH .

When it comes to ac systems people from Arizona seem to be more educated about this stuff.. no room for error.

as was mentioned you put just a little too much R134 in on a R12 system in the AZ heat , the system will blow up...over pressure !

also remove ac compressor and drain out all the mineral oil. then add the ester oil into the compressor .

I believe the total system would use about 8-9OZ. put about 3OZ into the compressor refrigerant line connection ports. the rest in the NEW filter dryer accumulator tank ..

OK, I'm at the point where I need to clear the oil out of the existing original compressor. What is the best way to do this without buying another expensive machine? How much of a pain is it to remove the serpentine belt and the compressor to drain the oil? Is it necesarry to drain the old mineral oil out of the compressor or will 134a run fine with it? If it will run fine with the mineral oil in the compressor, do I have to add additional oil with the refrigerant when I put it in? Another couple of questions?

I notice that the line containing the orifice tube (after I replaced the tube with a new one) only seems to screw back to about 1/2 of the threads. Is this normal or should it go nearly all the way?

I got a replacement accumulator/dryer. It has 3 schrader valves (it's a carquest). One is obviously for the switch and one if the low pressure connection, but what is the 3rd one for? My factory unit just has 2.

OK, I'm at the point where I need to clear the oil out of the existing original compressor. What is the best way to do this without buying another expensive machine? How much of a pain is it to remove the serpentine belt and the compressor to drain the oil? Is it necesarry to drain the old mineral oil out of the compressor or will 134a run fine with it? If it will run fine with the mineral oil in the compressor, do I have to add additional oil with the refrigerant when I put it in? Another couple of questions?

Serp belt is easy.....then remove the compressor(you will need new seals....you lube the seal/o-rings with mineral oil, not Pag oil)....drain the mineral oil from the compressor, at the drain plug and at the inlet and outlet opening, while manually rotating the clutch.......rule of thumb is, capture and measure the oil out of the compressor....if less than 2 oz, add 2 oz to the compressor at the drain plug hole....if more than 2 oz, add the same amount....but you will be putting 8 Oz total of Pag oil to the system......then manually rotate the compressor clutch to lube the compressor...

I notice that the line containing the orifice tube (after I replaced the tube with a new one) only seems to screw back to about 1/2 of the threads. Is this normal or should it go nearly all the way?

Should go back to the same amount of threads before removal...

I got a replacement accumulator/dryer. It has 3 schrader valves (it's a carquest). One is obviously for the switch and one if the low pressure connection, but what is the 3rd one for? My factory unit just has 2.


Don't worry about it....just use the same two as your original....

OK, I'm at the point where I need to clear the oil out of the existing original compressor. What is the best way to do this without buying another expensive machine? How much of a pain is it to remove the serpentine belt and the compressor to drain the oil? Is it necesarry to drain the old mineral oil out of the compressor or will 134a run fine with it? If it will run fine with the mineral oil in the compressor, do I have to add additional oil with the refrigerant when I put it in? Another couple of questions?

Serp belt is easy.....then remove the compressor(you will need new seals....you lube the seal/o-rings with mineral oil, not Pag oil)....drain the mineral oil from the compressor, at the drain plug and at the inlet and outlet opening, while manually rotating the clutch.......rule of thumb is, capture and measure the oil out of the compressor....if less than 2 oz, add 2 oz to the compressor at the drain plug hole....if more than 2 oz, add the same amount....but you will be putting 8 Oz total of Pag oil to the system......then manually rotate the compressor clutch to lube the compressor...

I notice that the line containing the orifice tube (after I replaced the tube with a new one) only seems to screw back to about 1/2 of the threads. Is this normal or should it go nearly all the way?

Should go back to the same amount of threads before removal...

I got a replacement accumulator/dryer. It has 3 schrader valves (it's a carquest). One is obviously for the switch and one if the low pressure connection, but what is the 3rd one for? My factory unit just has 2.


Don't worry about it....just use the same two as your original....

Like a dipshit I don't remember the original number of threads :P

I see a diagram for the serp belt but it doesn't say where to relieve the tension. I notice that to the right of the compressor is a round spring thing in a casing and below it is a pulley (I bet that's a clue), but there doesn't look like anything that I can put a 1/2 ratchet into and crank.

OK, I'm at the point where I need to clear the oil out of the existing original compressor. What is the best way to do this without buying another expensive machine? How much of a pain is it to remove the serpentine belt and the compressor to drain the oil? Is it necesarry to drain the old mineral oil out of the compressor or will 134a run fine with it? If it will run fine with the mineral oil in the compressor, do I have to add additional oil with the refrigerant when I put it in? Another couple of questions?

Serp belt is easy.....then remove the compressor(you will need new seals....you lube the seal/o-rings with mineral oil, not Pag oil)....drain the mineral oil from the compressor, at the drain plug and at the inlet and outlet opening, while manually rotating the clutch.......rule of thumb is, capture and measure the oil out of the compressor....if less than 2 oz, add 2 oz to the compressor at the drain plug hole....if more than 2 oz, add the same amount....but you will be putting 8 Oz total of Pag oil to the system......then manually rotate the compressor clutch to lube the compressor...

I notice that the line containing the orifice tube (after I replaced the tube with a new one) only seems to screw back to about 1/2 of the threads. Is this normal or should it go nearly all the way?

Should go back to the same amount of threads before removal...

I got a replacement accumulator/dryer. It has 3 schrader valves (it's a carquest). One is obviously for the switch and one if the low pressure connection, but what is the 3rd one for? My factory unit just has 2.


Don't worry about it....just use the same two as your original....

OK, I got the belt off and the compressor out. Not an easy task as bolts are in odd spots. I see the oil quantity on the compressor. Question is: I replaced the evaporator and there was very little oil in the compressor. How do I know how much ester oil to add to each of those parts of the system?

Update for the folks that are following this thread.

Added 5 of the 8 oz of oil into the compressor and the rest into the accumulator (hope that was right), put the whole shebang back together again with new O rings. Did I do it right? No clue yet - never done it before. Used Ester oil because I heard that PAG and old mineral oil systems don't mix. Tomorrow I'm donating more to the cause and spending $115 on a vacuum pump. Yeah I could get the cheap HF thing, but it would take too long to get here and I'm getting tired of being greasy. I'm going to evacuate the system and see if it holds a vacuum. If it does, I load 'er up!

Any advice before I dive in would be welcome.

did you not read how much oil I said to put in the compressor?

Less oil in the compressor would have been ideal, but it will live. You made the right choice in your oil selection. Good luck and Godspeed.

Well, I think I have less oil in the system overall now. I found a leak in the system. It is leaking from the threaded fitting which is (I believe) coming from the condenser and continues to the firewall (I don't know what to call this line). It is next to the battery and is the bottom-most steel line. I loosened and retightened this a few times and it just didn't feel right - like it wasn't screwing all the way in. I had changed the O ring on this fitting but I don't think it is tight enough to compress it and so it is leaking. It appears that replacement would involve a new evaporator and a new line running to the firewall. This is getting very expensive and I would like to just get that fitting to stop leaking.

I am VERY open to suggestion here.

Well, I think I have less oil in the system overall now. I found a leak in the system. It is leaking from the threaded fitting which is (I believe) coming from the condenser and continues to the firewall (I don't know what to call this line). It is next to the battery and is the bottom-most steel line. I loosened and retightened this a few times and it just didn't feel right - like it wasn't screwing all the way in. I had changed the O ring on this fitting but I don't think it is tight enough to compress it and so it is leaking. It appears that replacement would involve a new evaporator and a new line running to the firewall. This is getting very expensive and I would like to just get that fitting to stop leaking.

I am VERY open to suggestion here.

the line from the condenser to the evaporator would be the line which has the orifice tube[screen] in it . did you replace the screen. did you connect the correct line to it. normally you screw the nut and hold the line firmly from rotating .

the line from the condenser to the evaporator would be the line which has the orifice tube[screen] in it . did you replace the screen. did you connect the correct line to it. normally you screw the nut and hold the line firmly from rotating .

This is the line directly below it. It goes from the condenser to the firewall. It is not the line with the orifice tube in it. I believe it is the "cold" line.

Yes, I tightened it as you suggested above. Maybe the threads are messed up, but I can get it really tight and it still leaks - mostly out of the side of the line with the O ring. I just don't think that it is compressing the O ring sufficiently.

This is the line directly below it. It goes from the condenser to the firewall. It is not the line with the orifice tube in it. I believe it is the "cold" line.

Yes, I tightened it as you suggested above. Maybe the threads are messed up, but I can get it really tight and it still leaks - mostly out of the side of the line with the O ring. I just don't think that it is compressing the O ring sufficiently.

you did buy the O ring kit ? you cannot reuse these parts. replace the line O ring .

you did buy the O ring kit ? you cannot reuse these parts. replace the line O ring .

I did replace it. It just isn't screwing down tight enough.

I did replace it. It just isn't screwing down tight enough.

what can occur is if you used a tool that will crush the threaded nut you will have this effect. only use open end wrench NO PIPE OR VICE GRIPS ETC...

also you could have cross threaded the fitting which is hard to do but I guess possible if not careful.

what can occur is if you used a tool that will crush the threaded nut you will have this effect. only use open end wrench NO PIPE OR VICE GRIPS ETC...

also you could have cross threaded the fitting which is hard to do but I guess possible if not careful.

Finally got it tight and it is not longer leaking. Vacuumed the system and charged it. Ahhh....cool air :-)