Air conditioning and the VCM

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  #1  
Old 08-14-06, 04:25 PM
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Exclamation Air conditioning and the VCM

I am about fed up to here with the air conditioner on my 01 Pontiac Grand Prix GT 3.8 liter V6. Let me start out by saying that we have so far to date spent over 600.00 on this stupid thing here is the list of parts we have replaced the pressure switch, the compressor, the dryer, the orifice and most recently the VCM (on the advice of our local GM dealer). We have also repatedly had the fuses and relays checked. WE still can't get this thing to cycle on and suck freon. But the garage did a bypass and thats almost full anyway. So could someone please tell me what in the world is wrong. I need help I'm at my witts end here. We have to take a very long road trip soon and we need this A/C. Please help.
 
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  #2  
Old 08-14-06, 05:27 PM
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So for clarification, you bypassed or hotwired the compressor and it comes on and works ok? If so, then you have an electrical malfunction somewhere it sounds like...not in the parts but maybe the wiring?
 
  #3  
Old 08-14-06, 07:09 PM
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They bypassed it somehow through the relays and the pressure valve popped out when the compressor ran. That was before we replaced all those parts. The mechanic that did the bypassing said that all the voltage was correct down to the compressor but the computer wouldn't let it kick on. Could anything inside in the controls be causing this? All the controls seem to be working right ac light comes on the vents blow like they are supposed to. But we just don't know.
 
  #4  
Old 08-15-06, 05:02 AM
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Kristi,
I'm a little concerned this mechanic might not know what he's doing. The fact that he allowed the pressure relief valve to blow the charge tells me he wasn't monitoring the pressures. That was a huge mistake! The High pressure cut-off should have protected that from happening but it sounds like he bypassed it and didn't notice the system was going into an “over pressure” condition. Not all systems have a pressure relief but luckily yours did, or something much more expensive might have blown instead.

MVAC, isn't very complex and a good technician should be able to quickly determine why the compressor isn't engaging.

I think it's time you find a different shop to work on your A/C! ! ! ! In fact, if you paid the $600 on a credit card, you should file a dispute with your credit card company ASAP because your A/C did not work after you spent the money for the repairs.... An A/C shop should be able to tell you exactly what is wrong with you’re A/C system and should be able to supply you with an estimated cost to repair/replace parts and charge the system. Then, when the job is complete, they should supply you with a detailed report which will include the work performed, a parts list and a system performance evaluation. Anything less than that is unacceptable!

Without some specific information about your system like pressure readings, there's no way you can really get any help from a forum like this. It would be nothing more than a guessing game!
Good luck,
Phil
 

Last edited by DIYaddict; 08-15-06 at 09:01 AM. Reason: Removed quote as it's unnecessary
  #5  
Old 08-15-06, 05:11 AM
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phil is dead on...it's an electrical problem and you need a experienced electrical technician to sort it out. he's also right about the ethical issue of spending a bunch of money based on the advice of a professional and getting nothing for it.

frankly i don't understand why the compressor had to be replaced...was it because the tech blew the pop off valve? many of those are auto resetting or replaceable...
 
  #6  
Old 08-15-06, 07:38 AM
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Thanks guys but this money was all cash for parts not for labor my husband knows this guy so he took a look at it because he owns a repair shop. He just kept saying it might be this it might be that. He couldn't really tell what was going on because he doesn't have a computer to hook the car to. When we went to buy a part from the parts house we were told that you have to buy these other parts for there to be a warantee on anything. So thats why we had to replace all these different parts. So then we took it to the Chevy garage to have it hooked to their computer thats when they told us we had to have a new VCM. So we just got the computer and put it in yesterday the ac still doesn't work and the engine light came on today so I took it to Auto Zone heres the codes PO332 and PO327. I'm not sure what they are but the light never been on before we changed the VCM. Honestly it makes me want to cry.
 
  #7  
Old 08-15-06, 08:29 AM
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Originally Posted by Kristi
today so I took it to Auto Zone heres the codes PO332 and PO327. I'm not sure what they are but the light never been on before we changed the VCM. Honestly it makes me want to cry.
Kristi,
So AutoZone pulled the codes, gave you the numbers and didn't tell you what they meant? Wow, nobody wants to do anything anymore; they should have given you more information than just the numbers…….

Here ya’ go:
P0327=Knock Sensor Circuit Low Voltage
P0332=Knock Sensor 2 Circuit Low Input (Bank 2)

As for the warranty on A/C parts that's usually only the case with the compressor. Most compressor manufacturers will only warranty their compressor if you also purchase an accumulator/dryer too. But you should replace that anyway whenever you replace any major component or if the system has been open to the air for anything more than a few minutes during service.

You didn't happen to buy a remanufactured "Four Seasons" compressor did you?
If so, those are junk! ! ! ! Maybe that’s the problem? In fact, in the trade, they're usually referred to as "Four Seize-ens."

Sounds like things are going from bad to worse in a hurry! Honestly, you need to get the car to a reputable shop…..otherwise you could end up spending a lot of money guessing on which parts are bad and then, you might not even get the A/C to work, let alone figure out the VCM code problems!
Good luck,
Phil
 
  #8  
Old 08-15-06, 08:39 AM
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sadly, this is a classic case of someone who wasn't qualified to work on complex electrical circuits and not owning up to it. many folks are also under the false impression that because todays autos are computerized that the computer tells you what's wrong with the car and that just isn't so. the scan tool and on board computers just gather and display information, but that must always be looked at and evaluated on a logic basis, just as a doctor gets info from you (symptoms) and orders what tests he or she thinks appropriate and then correlates the results with the complaint.

at any rate...the basic electrical problem still exists and now you have spent big money for nothing. for the record, the dealer didn't do you any service either...someone didn't go the extra yard it takes to verify a diagnosis thru testing before telling you you needed a PCM.

the PCM does control the AC clutch relay and a scan tool is needed to verify the AC request signal is being "seen" by the PCM as well as inputs from the AC pressure sensor. it must also be determined if the relay has power to the coil side as well as the clutch side. if all of these things are correct, it only leaves a wiring problem which is the least likely cause. I gathered all of this from the wiring diagram for the AC on your car.
 
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