Volvo RWD 700 Forum

Hi folks,

So I tested my AC compressor by jumping the low pressure switch and it seemed to run with no problems, and silently, too - I was like, "wow, it sounds like it's new!" Turning the compressor by hand, too, there was no noise or resistance, and I heard bubbly noises in the receiver dryer. So, on the advice of a friend of mine who is an experienced mechanic, I used a charge kit and some R134a to further investigate my AC system.

The gauge on the low side told me that the charge was very low, near 0. I added some coolant from the can for like 15 seconds, and checked the pressure - it was very high, like 45psi. The compressor kicked on 45 seconds later, and made a sound like there were ball bearings in there. It only ran for like 2 seconds, and the pressure on the gauge began to drop to around 25psi. It climbed up to 45, compressor kicked on and off, pressure dropped, then the pressure climbed again, ad infinitum. With the AC off, I read 75psi steady.

I have never charged AC, so I don't know what to make of the bobbing needle on my gauge. Why would pressure steadily increase without the compressor on? Do I need to adjust the pressure switch to kick on at ~30psi?

Thanks for your advice. Please don't berate me for not visiting an AC shop, I didn't have the money and this was more an investigation than a repair.

Ari

I had to adjust the pressure switch screw. Afterwards, I was able to charge the system with no trouble, and my car cools down fast now. Thanks for the advice y'all.

Ari

Sounds fine.
Add refigerant just 'till the compressor stops cycling at 1500 rpm.
Though I must say, If the system hasn't been converted (oil, etc) and vacuumed, it's doomed to fail.

Factory R134a conversion done in 2001, it just got real low and hasn't been used in a while. I am prepared for the eventual replacement of the aged R12 components, but for the short term if it will kinda work, I just need it for winter defrosting.

Ari

As long as the system is working. If it is around 95 degrees outside and up, charge to around 50 to 55 with refrigerant 134. It only will read correctly when the compressor is running. It will pull down the pressure as long as your hooked to the low side of the system. When charged the compressor will pretty much run all the time. You will also hear the auxilliary fan kick in when the evaporator starts putting out cool air. Remember, 50 to 55 with compressor running. Good luck.

I have fixed the ac in 2 of my volvos and 1 dodge van. If there is one thing that I would definitely change, it is the receiver/drier. The old one is definitely finished and will probably hurt the system. A new one only costs about $25.

hello
you would also be silly not to change the orifice tube screen thinge.
ya gotta hate a.c. work.
good luck
mike