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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I have a 2004 chevy silverado and the ac is not blowing very

Customer Question

Hello I have a 2004 chevy silverado and the ac is not blowing very cold
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
Low side pressure is 70 and the highside is at 325. Engine running at 2k RPM.
Expert:  Ron replied 1 year ago.

Hello and thank you for you question, from looking at your reading you you have either an overcharged system or the compressor has failed. Normal pressure on a properly filled system should be right at 35 to 40 PSI on the low side and 200 to 225 PSI on the high side with the compressor running. If no Freon has been added then its most likely a failed compressor. If Freon has been added the you need to recover the Freon and evacuate the system and recharge it with the proper amount and recheck the operation and pressure readings. Post back if you need more help and or information and we can work from there.

Customer: replied 1 year ago.
The system was evacuated and recharged with 24oz of r134a. Compressor, condenser, and dryer have been replaced recently. And evaporator replaced today. Is it possible for the compressor to go out that soon.
Expert:  Ron replied 1 year ago.

Its not very common but if you have 70 PSI on the suction side (low side ) that sure indicates the compressor is not sucking the pressure down.

Customer: replied 1 year ago.
When the compressor turns off the low side pressure rises to over 150.
Expert:  Ron replied 1 year ago.

Both the low side and the high side should equal out and normal pressure on a properly filled system should be right at 100 to 110 PSI on both the low side and the high side with the compressor off. Are you 100% sure the system is not overcharged?

Customer: replied 1 year ago.
Parts house said the vehicle holds 26oz of freon. I only filled it with 24oz. Could there be a restriction
Expert:  Ron replied 1 year ago.

26 is the correct amount and in most cases if you have a restriction the low side (suction side) would go into a vacuum with the compressor running. and drop the low side pressure.

Customer: replied 1 year ago.
a restriction on either the high or low side would not cause this issue
Expert:  Ron replied 1 year ago.

Any type of restriction in the system would cause the compressor to go into a vacuum on the low side if the compressor is sucking as it should be.

Customer: replied 1 year ago.
if the compressor is bad both sides would read high like they do?
Expert:  Ron replied 1 year ago.

There are only two things that can cause the reading to be high on a running compressor , either the system is over charged or the compressor has failed.

Customer: replied 1 year ago.
Update I replaced the compressor. Gauges and vacuumed system and filled with 24oz r134a. Still not blowing cold and highside is at 275 and low is at 75. Any other ideas
Expert:  Ron replied 1 year ago.
Did you flush the system when you replaced all of these components, was the expansion tube replaced as well?
Customer: replied 1 year ago.
Removed orifice tube was clean.
Expert:  Ron replied 1 year ago.

Okay well then something is sure being missed here. Are you sure your charging system is accurate and you are actually adding the correct amount of Freon?

Customer: replied 1 year ago.
I am using proffesional gauges and I am adding two cans of freon.
Expert:  Ron replied 1 year ago.

Well with the reading is appears to be over charged. The system calls for 1.6 LBS so the level should be right. Something is being over looked here and at this point I am not sure what. You have covered everything I can think of. If you would like, I can open the question back up and see if someone else has anything new to add.

Customer: replied 1 year ago.
I would appreciate it.
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Give me a couple moments to review what you and Ron talked about.

Expert:  GM Tech (Cam) replied 1 year ago.

OK I have a question. During all the replacements, what happened to the oil in the system? Did you replenish any oil? Did you balance out the oil from the compressor? Also prior to this, what repairs or parts were replaced?

Customer: replied 1 year ago.
no we just added 3 oz of oil to the compressor , the compressor, evaporator, accumulator and all the lines were replaced
Customer: replied 1 year ago.
also the condensor
Expert:  GM Tech (Cam) replied 1 year ago.
then everything has been replaced?
Customer: replied 1 year ago.
Correct
Expert:  GM Tech (Cam) replied 1 year ago.

OK, do you get any cold air when driving at all now or is it just cool or outside temp?

Have you tried pulling out some of the refrigerant and putting in a bunch less? I am wondering if its possibly overcharged, and your cans while saying up to 24 oz actually contained more causing this. Can you pull some out and see what happens?

Customer: replied 1 year ago.
right now its blowing around 85 degree air out. I will try and pull a little refrigerant out and see what happens
Expert:  GM Tech (Cam) replied 1 year ago.
Sounds good.
Customer: replied 1 year ago.
ok just let out some refregerant the ac is still blowing the same temp out. when the compressor kicked on the pressure was 75 on low side and 325 on the high side.
Expert:  GM Tech (Cam) replied 1 year ago.

Ok so no change. The orifice tube, was that every changed?

Customer: replied 1 year ago.
we changed it and it was clean
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, so I would like to try flushing. What we do is recover the system, remove the orifice tube, put the line together and use our AC machine to flush fill the whole system with R134A, then pushes it all through cleaning EVERYTHING out. Then we put in new oil, 8 oz and charge it.

Expert:  GM Tech (Cam) replied 1 year ago.

Also let me ask this before we go to far, how long does the compressor run?