Question about 2001 Pontiac Montana

1 Answer

AC problem with 2001 Montana passenger van

I had an AC problem diagnosed by a professional firm and they determined my compressor is bad. Long story short.... I replaced the compressor, accumulator, and both front and rear expansion valves (2001 Montanna with front and rear air). I pumped vacuum for an hour, then filled with 2 lbs of R134a freon (spec is for 2.2 lbs.) Low side pressure at idle is 50 psi..... at 2000 rpm will drop to 40-45 psi. But high side stays constant around 200-250 psi. And air is only moderately cool coming out of vents.

Is it possible I purchased a bad compressor? It was a reman. I don't know what else it could be. I feel I have replaced everything that is reasonable.

Posted by on

  • 1 more comment 
  • JOHN DAVIDSON Jul 21, 2010

    The pressures seem adequate for cold air flow to be happening...did you put a few ounces of compressor oil in with the charge? If not evacuate a little and add a can of 134a with oil/freon mixture. Check the vents perhaps some of your air is escaping , the compressors are generally made well however it is remotely possible you might have a bad one. be certain the clutch is holding long enough, do your homework and see if this system has an a/c cycle switch that perhaps has gone bad? Hope this works. Happy motoring!!

  • lcwillisjr Jul 21, 2010

    I did put 2 ounces of oil in. Is there a way to tell if you have too much or too little oil?

    The compressor does engage and stays engaged. That indicates to me that the temp sensor doesn't get cold enough to kick the compressor off. I've removed the ducts and can place my hand right on the evaporator and is only mildly cool.

    Also..... when I shut the engine off the low and high side pressures seems to equalize withing a few seconds. I thought this took several minutes as the freon equlized through the expansion valves.

  • lcwillisjr Jul 21, 2010

    It has front and rear air, so yes I replaced both the front and rear expansion valves. No sight glass other than the one where the freon line leads into the AC guages. None on the system.

    I held off adding any more freon as the low pressure side was already reading 50psi even after adding 1.5 lbs of freon. I was hesitant to overcharge although I went ahead and added another .5 lbs bringing the system up to 2 lbs total. So I know I'm little under the 2.2 lbs specified at this point.

    It seems that if the compressor was working properly that the low side would have been lower (20-30 psi) and increase up to 45-50psi as I added the freon. :-(



1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.


    An expert who has written 7 tips or uploaded 3 video tips

  • Master
  • 630 Answers

Did you replace the expansion valve?
Also try adding just a little more freon and see if that makes a there a sight glass you can view with the system activated to be sure you have it completely air free?

Posted on Jul 21, 2010

  • JOHN DAVIDSON Jul 21, 2010

    Dont forget the ambient air temp(humidity etc.) has all to do with the variation of readings the more humid the higher pressure and the less cooling effect.

    If the lines are icing uo its probably from the humidity.



1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya Mechanic can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US.
click here to Talk to a Mechanic (only for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

I have a 2002 pt cruiser that is blowing the ac 10amp fuse repeatedly. I mean within minutes of changing it. Also the ac is only blowing hot air. Can someone please help.

An AC system blowing hot air is usually due to a low freon charge or a non operational AC compressor. If the fuse blows, disconnect the compressor electrical plug and turn on the AC. If the fuse doesn't blow, suspect a compressor problem. If the fuse continues to blow with the compressor disconnected, there is a direct short between the ON/OFF switch and the compressor which can take hours to diagnose

Sep 07, 2015 | AC Cars & Trucks

1 Answer

It's not working, AC , radio,or back up..will come on

it looks like you may have a bad A/V control unit. this is a very expensive part and should be diagnosed by a professional before replacing. Things like power, ground, and communication lines will need to be checked with proper equipment to determine if it is bad. on a side note these are fairly common failures in nissans. occasionally they will cause the vehicle not to start as well.

Sep 05, 2015 | AC Cars & Trucks

1 Answer

Vr Calais alarm is going off for no reason at least 5times a day:(help

buy a falcon... just kidding mate. it is probably and after market alarm yes???? hard to diagnose without knowing the brand, model and features or your alarm but long story short it is well worth the cost to get a professional to install a new one. the issues you are experiencing could be due to a rookie installing an alarm, a faulty sensor, bad earth, over sensitive shock/tilt sensor, shoddy constant....the list goes on. an alarm is worth doing it right.

Jan 03, 2015 | Cars & Trucks

1 Answer


Hi, no, they are not related. The oxygen sensor(s) are part of the ignition/emissions sytem and help regulate fuel flow/mixture. The A/C system is self contained and does not affect other engine systems. Mike

Jun 14, 2011 | 2009 Saturn VUE Hybrid

2 Answers

The ac compressor kicks on and off. We have had a professional look at it, but they couldn't find a problem. However, the compressor doesn't run long enough to get the air cold. Is this an...

Could be either. Usually if the compressor is cycling than its usually low on refrigerant. Could be pressure sensor. Could be cooling fan. I would have a different tech look at it. It is hard to diagnose what is going on without knowing pressures of the high and low side from a gage hooked up to the system.

Jun 06, 2011 | 2004 Chevrolet Venture Passanger

1 Answer

Air conditioner stopped cooling. Dealer diagnosed evaporator leak, replaced the evaporator assembly, expansion valve, drier, evacuated and charged the AC system. One week later, AC stopped cooling,...

It could be that there was more than one leak and the dealer found only one. The AC system has two pressure switches to protect the compressor from damage---a low press. switch cuts off the compressor when there is not enough refrigerant in the system, the high switch cuts off when pressures get so high they could blow out the seals. Both are a result of a leak--refrigerant leaks out and air can leak in. Air will compress and when it does, it gets hot--so no cooling, and pressures go way up. So the compressor may have been stopped by those protective switches.

Of course, there could be a bad relay or other circuit malfunction.

Another possibility is that the compressor sat too long before being repaired (but we are talking about weeks going by here, not days). The air and moisture (humidity) that leaks into the system during this time creates acids that will attack the metal reed valves in the compressor. On restart, the damaged metal valves eat themselves in short order. If this is the case, the compressor ran until it seized and will need to be replaced. This particular problem is impossible to diagnose. So the dealer may have done his best.

Feb 12, 2011 | 2002 Honda Accord

1 Answer

Engine gets very hot; air conditioning shuts off

It needs to be diagnosed. It's normal for the AC to shut down when the engine overheats. The engine computer (called the ECU - Engine Control Unit) monitors the coolant temperature by means of a coolant temperature sensor (cts). When this sensor tells the computer the engine is too hot (above 230 to 240 degrees), the ECU turns off the AC compressor and the cooling system fans go to MAXIMUM (HIGH) speed. By the way, there are two engine/coolant temp sensors - one for the instrument gauges, the other for the ECU. If this sensor is malfunctioning, it can cause the symptom you describe - BUT that needs to be verified. Best solution, take it back into the mechanics/technicians and have them determine if that's all this is, because if it isn't, something else could be seriously wrong (clogged radiator, malfunctioning water pump, bad thermostat (even though it's new (or maybe it didn't actually get replaced), and there's a slew of other possible causes.. leaking head gasket for one. Best have the professionals (if they are professional) diagnose it.

May 25, 2009 | 2000 Hyundai Sonata

4 Answers

Ac not working

I had the same problem with the over temp sensor on the compressor. I had it repaired at the dealer for $200.00 plus. I just had the same problem reoccur. This time I bypassed the switch myself.

There is a small wire harness that runs from the compressor above the radiator, inside there are three wires. After determining which ones to jump " two smaller gage blue" the AC system works fine in all modes.

Thanks "Guset"

Jun 30, 2008 | 2003 Honda Civic

Not finding what you are looking for?
2001 Pontiac Montana Logo

871 people viewed this question

Ask a Question

Usually answered in minutes!

Top Pontiac Experts


Level 3 Expert

77514 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22306 Answers

Jeffrey Turcotte
Jeffrey Turcotte

Level 3 Expert

8826 Answers

Are you a Pontiac Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides