A/C Compressor Clutch not Engaging


Maulsmasher
04-25-2008, 10:31 PM
My compressor will not engage! There is no cold air. Okay, I have been researching and diagnosing my system. The system has freon, the wires seem okay, the fuses are fine (I didn't check the relay, not sure if that could be a cause). To add the belt is fine, the condensor is free of debris and dents.

I'd like to diagnos the compressor better, but I am unsure what the next steps should be.

Any help is appreciated. Thank you.

old_master
04-26-2008, 12:32 PM
Year, make, model and engine, and is the HVAC system manual or automatic climate control? Do you have a manifold gauge set for checking the system? (All of this is necessary) What are hi and low side pressure readings with A/C in MAX position, windows closed, blower on hi speed, and 1500 engine RPM?

JC327
04-28-2008, 01:20 AM
There's a black two-prong connector on the accumulator (big silver can) that connects to a switch that prevents the compressor from engaging if the system has insufficient pressure. Have the engine running and AC on, unplug the connector, and bridge the contacts on the plug itself with a piece of wire used as a jumper (even a paper clip will do). If the compressor engages, the problem is probably low pressure. If it does not, the switch needs to be replaced.

Maulsmasher
04-28-2008, 12:06 PM
Thank you for responding, sorry for the delayed replay:

1999 Chevey Blazer V6 engine, manual A/C controls, I do not have a manifold guage set, but I do have access to one if need be...

JC327
Thank you, I will try that and post the results. If I bridge the contact that bypasses the low pressure cut-off?

If I do need to replace the switch I am guessing the system needs to be evacuated...is that correct?

What about the relay...cold that be the cause? Does a relay go often or would that be rare?

Gabe25
04-28-2008, 12:31 PM
The switch that JC327 is talking about is called a Cycle Switch. If you need to replace it. Just un screw it and screw the new one back on. The switch is actually screwed onto a shreder valve. So you don't have to evac your system. If you still haven't gotten the compressor to ingauge. Try disconnecting the wire that plugs into the rear of your compressor. With the ignition switch on, apply ground to the contact on the rear of the compressor. Your clutch should operate. If not, that switch needs to be replaced. Bad thing is you'll need to purge your system in order to change the switch.

Maulsmasher
04-28-2008, 12:59 PM
Gabe25

Thank you for the reply. I will start with the "cycle switch" and go from there. I'm just hoping I do not need a new compressor and diagnosing as much as i can myself will hopefully leave no surprises if i do have to take in in to get serviced.

brcidd
04-28-2008, 01:29 PM
If you still haven't gotten the compressor to ingauge. Try disconnecting the wire that plugs into the rear of your compressor. With the ignition switch on, apply ground to the contact on the rear of the compressor. Your clutch should operate. If not, that switch needs to be replaced. Bad thing is you'll need to purge your system in order to change the switch.

I'm sorry, but that switch is a two wire switch on the back of the compressor-- the wiring diagram clearly shows the input is from the control head 12v+ and the output goes directly to the PCM to shut off the compressor when head pressure is above 425 psi-- it is a normally closed switch and opens at high head pressure. If you ground either terminal you will either blow the control head fuse or possibly damage the PCM-- so why would you tell him to do that?-- you are thinking of the old 1- wire switches- back at about 1992 vintage-- this is clearly a 1999--- things change over time.

I believe he has a leak- when you jumper the cycling switch the compressor will most likely come on- don't run it that way for long---most common leak location on your truck is the compressor "belly" o-rings- look for oil/greasy build-up on the bottom of the compressor and on the engine cradle that holds the compressor.....

Gabe25
04-28-2008, 02:24 PM
Thanks Brcidd, Your right. I thought I saw his year as a 94 not a 99. I stand corrected. Do not apply ground.

Maulsmasher
04-28-2008, 02:26 PM
Thank you. If I find a compressor leak does that mean the compressor is shot and needs replacement?

brcidd
04-28-2008, 03:05 PM
For most it does- But I reseal them- put all new seals and o-rings in them- As long as the pump can generate pressure and you have the proper tools it can be done.....

Maulsmasher
04-28-2008, 03:21 PM
I plan to test the "cycle switch" when I have the chance, but it is raining at the moment.

As for the compressor...that becomes out of my league...I think I'd have to take it to be replaced. I am ok with diagnosing the A/C, but I'm not confident in the least to attempt to mess with it. I just don't want to spill $500 into it if the problem is simple.

Maulsmasher
04-28-2008, 03:36 PM
:runaround:
I'm not sure if this is related or even an issue, but I have noticed a hiss coming from the A/C controls in the car....It occurs everytime I switch the controls over to a new setting...then a hiss that fades away...is this normal? It has been doing it for a while, but I never really paid much attention to it...

brcidd
04-28-2008, 03:55 PM
That hiss is normal- it is the vacuum actuated mode door actuators being driven by the vacuum switch at the control head- vacuum is applied and vented as you rotate through the different modes at the control head. You have about a 10% chance of a faulty cycling switch-- you have about a 70% chance of a leak in the system--- just playing the numbers from my database of a/c diagnostics....

Maulsmasher
04-28-2008, 04:19 PM
I just checked and bridging the connector of the cycle switch made the compressor engage...

So is this a definant sign of a leak? The compressor still did not engage after I added freon to the system. I don't see any visual signs of a leak. Should I go for dye in the system to hunt for a leak? Or should I diagnose the cut-off switch?

MT-2500
04-28-2008, 06:46 PM
The cycle switch will shut off if low side is below around 25 lbs.

You really need to get the recharge gauges on it and check low side and high side pressures.

Hook up the gauges and if compresser does not turn on jumper the low switch and see if the high side goes up to 150-250 lbs and if low side stays over 25 lbs.
If low side is down under 25 and hight side is not over 200-250 add some R-134a.
After low side comes up to 28-30 the cycle switch should run compresser.
If not go for a new cycle switch.
Also watch plug in for a lose wire or connection.
If low side is low and high side is low you are low on R-134A
MT

Maulsmasher
04-28-2008, 10:29 PM
MT-2500

Thank you. I will get the guages on it this weekend, I need to borrow it.

I have not used them before, is there anything i should know to be cautious when using them?

MT-2500
04-28-2008, 10:39 PM
MT-2500

Thank you. I will get the guages on it this weekend, I need to borrow it.

I have not used them before, is there anything i should know to be cautious when using them?

You are welcome.
They are plug in and play.
Just hook them up and go.
Lot safer than the wall mart one hose one can death kits.
You can read low and high at same time.
If high side starts geting up over 350 shut it down and remove some R-134.
To much freon and the high side pressure goes up fast and high.
When it goes over 500 I run out the back door.
Good Luck.
MT

Maulsmasher
04-30-2008, 02:29 PM
Ok here is a wierd occurance, ever since I used a jump wire on the cycle switch the compressor kicks on and off...but only for a few seconds on and a few off. It is hard to tell if the A/C is blowing cold at the moment as the weather has been in the 50's the past few days...any ideas...low pressure?


seperate question, I have not had a chance to get the manifold guages on it yet, what type of connections do i need on the manifold guages? The ones I have access to are used on home a/c system, I haven't had a chance to look at it yet, but i'd imaging a different type of connector...

MT-2500
04-30-2008, 03:55 PM
Ok here is a wierd occurance, ever since I used a jump wire on the cycle switch the compressor kicks on and off...but only for a few seconds on and a few off. It is hard to tell if the A/C is blowing cold at the moment as the weather has been in the 50's the past few days...any ideas...low pressure?


seperate question, I have not had a chance to get the manifold guages on it yet, what type of connections do i need on the manifold guages? The ones I have access to are used on home a/c system, I haven't had a chance to look at it yet, but i'd imaging a different type of connector...

You need to get the gauges on it.

You need R-134a QUICK COUPLERS ON a GAUGE SET TO PLUG ON TO YOR R-134A SYSTEM.
Most home AC have went to R-134a couplers and gauge set.
Give us your readings low and high side at idle and at 2K RPM.
If compresser does not run jump it and get readings with compresser jumped/running.
MT

MT-2500
04-30-2008, 04:00 PM
http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

Maulsmasher
04-30-2008, 04:01 PM
Thanks, I plan to get the guage on it as soon as I have the chance. I will post my readings.

Maulsmasher
05-06-2008, 09:18 AM
Just a quick update:
I am in search of the proper R134 fittings/hoses for the manifold guage I borrowed as it isn't equiped with the proper hoses. Any suggestions on a good place to buy R134 hoses for a manifold guage? The less $$ the better and I prefer a store rather than purchasing online. Thank you.

MT-2500
05-06-2008, 09:31 AM
Just a quick update:
I am in search of the proper R134 fittings/hoses for the manifold guage I borrowed as it isn't equiped with the proper hoses. Any suggestions on a good place to buy R134 hoses for a manifold guage? The less $$ the better and I prefer a store rather than purchasing online. Thank you.

Most of your local auto parts place have them.
Here is a picture of them online.

http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=DIY

Maulsmasher
05-06-2008, 10:38 AM
Excellent, thanks again.

MT-2500
05-06-2008, 11:13 AM
Excellent, thanks again.

You are welcome.
Unless you use adapters you will have to have a R134a manifold for the hoses to fit it.
Different threads on hoses and couplers from R-12 to R134a.
Good luck
MT

Maulsmasher
05-06-2008, 02:29 PM
Seems like the r134 hoses ($39.88) they have at Advance Auto will fit the manifold guage, but I didn't have the guage with me to see, so i did not purchase yet. While there I saw this (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=IDN&MfrPartNumber=HGT134ACS&CategoryCode=3569). It is one guage that says it is a high and low pressure guage...does it only read one at a time?

http://www.partsamerica.com/product_images/img/idn/hgt-134acs.jpg

MT-2500
05-06-2008, 03:36 PM
Seems like the r134 hoses ($39.88) they have at Advance Auto will fit the manifold guage, but I didn't have the guage with me to see, so i did not purchase yet. While there I saw this (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=IDN&MfrPartNumber=HGT134ACS&CategoryCode=3569). It is one guage that says it is a high and low pressure guage...does it only read one at a time?

http://www.partsamerica.com/product_images/img/idn/hgt-134acs.jpg

That one does not look like a very good deal.
No quick couplers for R-134a.
And you can only read one side at a time with only gauge.
I would add a few bucks to that one and get the mainifold and twin gauges and quick couplers.

You might also check you local parts place and see if they have a loaner or renter on the gauge set.

Maulsmasher
05-06-2008, 03:45 PM
Ok, I think I'm going to get the hose set (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=IDN&MfrPartNumber=BRY134HD&CategoryCode=3569) as long as if fits on the manifold guage i currently have.

http://www.partsamerica.com/product_images/img/idn/bry-134hd.jpg

MT-2500
05-06-2008, 03:54 PM
Ok, I think I'm going to get the hose set (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=IDN&MfrPartNumber=BRY134HD&CategoryCode=3569) as long as if fits on the manifold guage i currently have.

http://www.partsamerica.com/product_images/img/idn/bry-134hd.jpg


You are on the right track now.
Good looking long hoses.
Where the hose goes onto manifiod you may need the 3 brass fitting pipe thread in manifold to R-134A HOSE.
Take the gauge set with you and get all of the right stuff.
Good luck and let us know how it goes.
MT

doug7x
08-13-2008, 09:25 PM
Hey, folks...I'm new to the Cav. forum...usually on the Geo Metro side, but my Metro is out of action for a while & I picked up a '97 Cav. to get me around for a while. (had several old Cavs before...always liked them, but 4.00 per gal gas & a 104 mile daily round trip got me into the Metros).ANYYYWAY...I've been following this thread...I have the same problem with my Cav. ('97-2.2-auto,..manual A/C). I knew about the low pres switch, so I added a 12oz can of 134a/oil/sealant. I could tell when I added it that there was pressure in the system, so I'm pretty sure that there's enough to run it. Clutch would not engage (green A/C light on dash DOES come on). Will the troubleshooting that is mentioned in this thread apply to my '97?, & if so, any other tips you can toss me would be greatly appreciated. ....Thanks in advance....Doug7x

MT-2500
08-14-2008, 08:49 AM
Hey, folks...I'm new to the Cav. forum...usually on the Geo Metro side, but my Metro is out of action for a while & I picked up a '97 Cav. to get me around for a while. (had several old Cavs before...always liked them, but 4.00 per gal gas & a 104 mile daily round trip got me into the Metros).ANYYYWAY...I've been following this thread...I have the same problem with my Cav. ('97-2.2-auto,..manual A/C). I knew about the low pres switch, so I added a 12oz can of 134a/oil/sealant. I could tell when I added it that there was pressure in the system, so I'm pretty sure that there's enough to run it. Clutch would not engage (green A/C light on dash DOES come on). Will the troubleshooting that is mentioned in this thread apply to my '97?, & if so, any other tips you can toss me would be greatly appreciated. ....Thanks in advance....Doug7x

You need to go to thw cav, forum and run a New thread/post there.
Your best tip is you done killed it if you added sealant any oil to it.

Wal Mart DEATH KITS

You cannot properly and safely recharge an air condition system with them.

The one side stop and go gauge does not tell you what your system is doing or is over charged or undercharged.
A overcharged or malfunction air condition system can reach over 500 lbs of pressure.
Enough to blow up that can or system and freeze you at first and the burn you or blind you and if any propane /butane in there blow and light you up.

The stop leak crap and who knows what kind of oil in the kits there will stop your system for sure.
Just like pouring super glue in it.
And some kits even contain freon with a butane mixer.
Good for a big blast.

If you are going to do it do it right and safe.
Here is what you need to start with.
http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

In the older days you could just throw in a can and go.
But over the years just adding freon is getting harder to do.
Newer systems have to have the correct amount of freon down to the ounces.
Most will need pumped down and vacuumed down and the right and amount of oil and a set amount freon charge installed to get the air to cool right and the system to last.
If an air condition is low there is usually a leak that needs fixed and also a lose of lubricating oil from system.
Also air and moisture enters a low system
If you are going to try to do it get the proper type air condition gauge set with the low and high side gauges.
Hook up the gauges and get a reading with compressor running at idle and at 2000 rpm on the high and low side.
Post back pressure reading and we can help you.
MT

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