A/C doesn't go on at all

[vintshave]

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

[Tech II]

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.....

[vintshave]

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?

[silicon212]

Originally Posted by vintshave

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).

[vintshave]

Originally Posted by silicon212

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!

[vintshave]

Originally Posted by silicon212

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?

[j cAT]

Originally Posted by vintshave

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..

[vintshave]

Originally Posted by j cAT

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.

[j cAT]

Originally Posted by vintshave

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.

[vintshave]

Originally Posted by j cAT

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.

[Blt2Lst]

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..

[Tech II]

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.......

[vintshave]

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?

[Tech II]

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

How did you get the compressor to run?

[vintshave]

Originally Posted by Tech II

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?