AC System Fooling Around

[E36M3]

I want to know why my wife's '97 QX4 ac system blows cold air only when the vehicle is at full stop. As soon as the vehicle starts rolling it starts blowing warm air. I checked the pressure from the low side and it has 47psi of pressure. I'm baffled about this. It just started happening yesterday. Can someone help? Appreciate the help!

[Leo1998]

The condenser may be dirty and needs to be cleaned. Start the a/c and see if a piece of paper gets sucked (stuck) to it, if not then not enough air flow.

[E36M3]

The condenser may be dirty and needs to be cleaned. Start the a/c and see if a piece of paper gets sucked (stuck) to it, if not then not enough air flow.

Thanks Leo. This maybe a dumb question but where do I place the paper?

[E36M3]

The condenser may be dirty and needs to be cleaned. Start the a/c and see if a piece of paper gets sucked (stuck) to it, if not then not enough air flow.

I did the paper test and the suction is very strong. What else can be the problem?

[Leo1998]

How did you check the pressure on the low side? Have you added any R134 since you've owned it?

[E36M3]

How did you check the pressure on the low side? Have you added any R134 since you've owned it?

No I have not added freon sinse purchased. I bought AC pro in pep boys that comes with pressure gauge. I start the car, turned on the AC to high, put the pressure gauge and it read 45 psi.

[Leo1998]

I would add R134 and see if that helps, I have a '98 and added some this year so yours is probably due, check the back of the can and add the amount according to the ambient temperature of where you live, I think i add 50psi( can't find my gauge...lol) Here's a video to give you an idea how to do it from AC Pro.

Edit: Actually i remember it was around 40 psi.

[Leo1998]

https://www.youtube.com/watch?v=-p2WzuoSHHA

[Leo1998]

I'm in Baja California...This may help, http://www.ambientweather.com/cuunsttemap.html

[E36M3]

I would add R134 and see if that helps, I have a '98 and added some this year so yours is probably due, check the back of the can and add the amount according to the ambient temperature of where you live, I think i add 50psi( can't find my gauge...lol) Here's a video to give you an idea how to do it from AC Pro.

Edit: Actually i remember it was around 40 psi.

thank you. It's blowing cold air.I set my ambient temperature in the pressure gauge to 100 degrees I tried filling it up 55 psi but it won't there. According to the pressure gauge it stopped somewhere around 50 psi does that mean it's already full?

[atraudes]

If your pressure is fine, adding fluid will do nothing. A/C systems, like brake systems, don't need to be "topped off" unless you have a leak. If you have a leak, fix the leak. If the pressure was too low it wouldn't blow cold under any circumstance.

This really sounds like a faulty compressor clutch. Does it continue to blow cold air when you increase engine RPMs while in park? Does it stop blowing cold if you let it sit for a few minutes in park?

It may be worthwhile to double-check the belt tension that goes to the compressor. I would think that if it was too loose you'd hear some serious squealing, but it's worth a peek.

I believe there are some clutch troubleshooting/diagnosing steps in the FSM. Have a read through that and see if that sparks any ideas or clues for you.

[E36M3]

It will blow cold air now even if the RPM increases. I was only curious if the fill amount inside the compressor should be more than 45 psi. I guess it will not make a difference. I guess my freon was a little low but it is fine as of right now. Thanks for all the help.

[Leo1998]

Your welcome...I'm pretty sure you can't overfill the unit with freon because of the amount they (mfg's) put into the cans.