Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

Intermittent Remanufactured Clutch Operation

mikosh6 on Sat December 29, 2007 2:01 PM User is offline

Year: 2000
Make: Pontiac
Model: Sunfire
Engine Size: 2.4L
Refrigerant Type: R-134a
Ambient Temp: 25F
Country of Origin: Canada

On this car if the refrigerant pressure sensor doesn't see a pressure change when A/C is called for does the PCM shut off power to the compressor clutch? How fast does this happen?

The old clutch assembly had a very noisy bearing when idling but it always engaged reliably. I had a re-manufactured clutch assembly installed. The re-manufactured clutch sometimes didn't engage. The shop that put it on said the air gap probably needed adjustment. They finally decided the unit was defective and installed another. However, the same thing is happening. I did some checking myself and found the PCM is not grounding the clutch relay coil ( measured with a DMM ) whenever the clutch doesn't engage.
From the workshop manual it looks like the only way the PCM can tell if the clutch engages or not is by feedback from the Refrigerant Pressure Sensor. Hence my questions above. Any other suggestions welcome!

Chick on Sat December 29, 2007 5:16 PM User is offlineView users profile

The pressure transducer (three wire switch) tells the ecm to sned ground to the relay..So you can try changing the transducer, do not jump any three wire switches and it can damage the ECM..Make sure the clutch gap is set properly, your compressor does not cycle, so it's either on or off when AC is called for....Hope this helps..

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

mikosh6 on Sat December 29, 2007 9:01 PM User is offline

Thanks for the fast reply Chick.
Since the clutch was the only thing replaced it would seem to make sense that it is probably the problem. If the air gap is incorrect stopping the clutch from engaging would the PCM normally detect this through the pressure transducer and shut down the A/C?
Thanks,
Mike

Chick on Sat December 29, 2007 9:14 PM User is offlineView users profile

No, the clutch gap adjustment would just stop the compressor from engaging. You can try a used trasducer to see if that is the problem, they are cheap enough for GM cars, I always have a few on hand since it does fail at times. There is a shrader valve under it, so there will be no loss of refrigerant when you change it.. But also look for broken, or shorted wires in the harness... AcDelco part number 15-5742 for a new one..Hope this helps.

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

mikosh6 on Sun December 30, 2007 10:49 AM User is offline

I'll concentrate troubleshooting to the pressure sensor and its circuitry and also the A/C request circuitry from the dash switch.
It seems like the air gap isn't a problem since every time the clutch won't engage I find the PCM is not allowing it to.
Thanks again for your help and advice Chick. This is a great site!

Chick on Sun December 30, 2007 5:18 PM User is offlineView users profile

if you want to check the clutch gap, just, very carefully, tap the front hub when the ac is on, if it is a clutch gap problem, the tapping inward should engage the clutch..But it sounds to me to be either a relay or the tranducser..Never jump a three wire switch, as you can damage the ECm..They work with something like 5 volts... The ohms vary "greatly" with temp and pressure, which is why I just screw a new (or used) one on to test it fast..Hope this helps.

PS: if you do get 12volts to go to the compressor and it still doesn't engage, pull the plug off and make sure the "pins" aren't bent over..Seen many techs bend them....

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

Edited: Sun December 30, 2007 at 5:19 PM by Chick

NickD on Mon December 31, 2007 7:15 AM User is offline

Dang limited lubricated bearing again, and a pain in the butt to change, think you have the V5 compressor in your car and very easy to damage the compressor seal if the new clutch is not installed properly. Can be blaming the thermistor when it well may be doing it's job. If the seal was damaged, you probably lost most if not all of your refrigerant, time to put gauges on it just to make sure you still have a charge.

Clutches are easy to check, just an electromagnet, gets 12 volts, should pull about 3.5 amperes and snap in hard, as the coil heats, the current should start to decrease. The gap should be properly adjusted when the hub is installed and requires a cheap feeler gauge with very close attention that the key is installed after the hub is installed as it can be jammed into the seal.

The only thing that holds the hub in place is friction, here you do not oil nor clean the compressor shaft, and should be a struggle when doing the last few turn on the hub installer. If the remanufactured hub had the bore cleaned, may be just too loose, pressed in tolerances are extremely tight, in the order of 0.0001 inches, I actually use salt water as a lubricant hoping the shaft will rust tight to the hub to hold it in place, one time, GM rust is good.

Cast iron is like glass that hardens with age, easy to peen in a bearing when the cast iron is fresh, but a bitch after it ages, tends more to chip than to form. Have no idea why GM is sticking with this stupid approach, never a problem like this with the old A-6, only thing that changes is with each different compressor, you need a different hub puller installer tool.

It is possible to get too rough with these things and even bend the compressor shaft just enough to cause a seal leak, would have a talk with your installer.

mikosh6 on Mon December 31, 2007 9:43 AM User is offline

Thanks Nick.
It is the V5 compressor. When I found the PCM wasn't grounding the control side of the clutch relay, I removed the relay and jumpered the clutch directly across. It pulled in immediately and the engine cooling fan started. The problem is frustrating; I set up to check the dash switch side of things yesterday and the A/C started up every time; must have turned it on and off 30 times. Came home from a trip last night, pressed the A/C button and nothing. If I turned off the ignition, restarted engine and pressed it again chances are the A/C would have turned on. ( This has happened previously. ) Its chilly here in Ontario, Canada now so its not easy to check if its still cooling ( its just handy this time of year for defrost ). Don't have access to gauges myself to check refrigerant. I'll have to rely on the local shop to do that.

Chick on Mon December 31, 2007 11:48 AM User is offlineView users profile

I wouldn't worry to much about pressures while it's that cold, ( hard to be acurate under 70 degrees) the problem sounds electrical.. Try the trasnducer "after" cleaning the terminals on the control head..Hope this helps.

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

NickD on Mon December 31, 2007 12:07 PM User is offline

Maybe nothing is wrong, ha, I forgot it's winter time, not that my hand froze to my snow thrower yesterday. When the ambient drops below 45*F, R-134a static pressure drops below 40 psi and that thermistor tells the ECM not to switch on the compressor. Course, the engine raises the underhood temperature, that also raises the static pressure, so the compressor will engage at much lower ambient temperatures.

Also have a V-5, when I switch to defrost, the green compressor light comes on that is kind of dumb when it's cold outside, but the compressor is not running. May start to run as the underhood temperature increases, may not, depending upon how cold it is outside. When you have erratic compressor operation in this kind of weather, pay attention to the outside temperature.

I have added a very neat under dash switch in the past to prevent compressor operation as in cold weather, it's very rough on the compressor, my car also switches on the compressor in the recir mode, even though the compressor switch is off. There really isn't that much moisture in the air when it's darn cold outside. I haven't done it to my latest cars as the wife drives them and those extra switches will confuse her, just let it fry. Also mounted a radiator thermistor to fire up the fan when the radiator reached 160*F rather than have the radiator near boil over before the fan kicked on. Really saves the engine from that additional thermal cycling and on a hot day in traffic the temperature sits at exactly at 195*F where it should be.

Not original ideas, the Japanese were doing this in Honda, Toyota, and Nissan cars, maybe why they lasted so long without problems, even used shims in the compressor. And when you switched off the compressor with the dash switch, it stayed off, Get the feeling that Ford and GM want you to have problems so you will buy a new car for them. Only 3K and 3 months past warranty and the strut bearings are headed south on my Cavalier, they did come out with an improved design that is more like the old design. Think I am going to buy another GM car? Screw them, what idiot decided to mount the thrust bearing in the upper spring seat instead of the mount where it belongs. Not protected from road salt where it's at, if the GM CEO were handy, would love to drive this car up his butt.

mikosh6 on Mon December 31, 2007 12:51 PM User is offline

The not working because its cold idea I hadn't thought of. It's around 28 - 32F here the last couple of days. But I was sure the A/C always came on at much colder temperatures, prior to the clutch being replaced. I found it really helpful to prevent those bad windshield frost ups when dry powdery snow starts to melt on the heater core! If the ECM is shutting off the A/C due to temperature is it directly measuring it using a sensor on this car or using the refrigerant pressure transducer? Excuse these basic questions; I'm pretty good when it comes to electrical stuff but not that knowledgeable when it comes to A/C. I'm starting to think of delaying further troubleshooting until spring!

Chick on Mon December 31, 2007 1:47 PM User is offlineView users profile

The trasducer sends the refrigerant temp and pressure to the ECM, at those temps the AC will not come on, that is until underhood temps rise, then it should come on for defrost.. Of course best way to test it is to wait til the car is "fully" warmed up then test it..Or get it into a heated garage and then try it.. Shutting down when cold prevents liquid refrigerant from slugging the compressor..

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

mikosh6 on Mon December 31, 2007 1:58 PM User is offline

Ok. I'll watch what happens after the car has been run for sometime. There may be nothing wrong here. Sorry I didn't mention the cold temperatures in my initial post.
Thanks to you both for your help.

GM Tech on Mon December 31, 2007 9:05 PM User is offline

Your a/c will engage when Pressure transducer sees 47 psi or greater- if it is 40 degrees out your system pressure will be near 40 psi-- so no a/c until the engine compartment warms enough to produce 47 psi or greater-

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.