Odd AC Question
 

Hi, I have what I hope will be a fairly quick question.

I have a 2006 2.3l mazda3. The ac compressor seized about 6 months ago, no leaks.

I'm trying to fix it myself and have done the following:

(1) replaced the compressor with a salvage one and
(2) put a new drier in. I then
(3) pulled a vacuum on the system for about 30min at 28Hg, and
(4) made sure there was no leaks with vacuum off for 5min.
(2) While still under vacuum I put R134 in high side until pressure at low side read 14psi (per manual instructions), this only took an ounce or two
(5) then shut high side and added rest of can to low side (so about 12 oz of r134).
(6) static pressure (ac clutch not engaged) is about 100psi, 75F temp outside)
(7) turned car on and hit ac button, clutch engaged immediately and pressure on low side dropped to about 10 psi and then started to climb, roughly 10 seconds after clutch engaging the low side had risen to about 60 psi and was still climbing, at that point I heard some squealing and shut ac off. I looked over at high side and noticed it was lower than low side reading (but this was when the clutch was now off, didn't see value when clutch was engaged). If I let the system sit a few minutes the pressure equalizes across the two as you would expect.
(8) I took it to a local shop and they said the system looked clean and that it was my compressor.

I ended up buying another compressor, expansion valve, and receiver dryer to try it again. Unfortunately the same exact thing happened again and I'm at a loss as to what to check now. Any suggestions?

Just a bit more about it. This time I measured by weight. The manual says 17 oz for the weight. I put about 7 oz in by weight and turned the car on with the a/c. At first, the low side pressure dropped to less than 5 psi and climbed to about 60 psi with high side pressure at about 130 psi. At about this low side pressure, the belt starts to squeal or some noise near the compressor. With the compressor off, high and low side pressure is a little over 80 psi. The outside temp is about 95F.

One other thing. The manual says the system take 5.25 oz of oil. When I took off the original compressor, 2 oz of oil were in it. When I put the new compressor in, I added 4 oz to the compressor, 2 oz for the compressor and 2 oz for the refrigerant. This was all poured into the low side port and compressor was turned a few times by hand. So, the manual says about 1.50 oz should be in the condenser and evaporator total, so my 4 oz plus the 1.5 oz is roughly 5.25 oz.

Everything has been replaced now with new parts except the evaporator and condenser. While I haven't drained the oil out of either, the oil that has dripped out in between the connections appears to be clean and clear. The original seized compressor also had clean oil.

the left over oil in the system may be causing you to overfill it. I'd use the vacuum or air hose through the lines to purge them to make sure any oil is out, and remove any particles of the original compressor that may be in there... then vacuum it again, and refill.

If the low side pressure rises above the high side - that seems impossible... not sure how that would happen. It is possible the low pressure drops too far, trips the compressor off and causes some fluctuation in the readings you're taking? or do you have two pressure gauges hooked up at the same time?
There are specs on the pressure switch to let you know what's good / bad.

If the ambient air temp is 95F your system should be 50-55psi. If your system is over pressured it will blow warm

When creating the vacuum it should be done at 29.9 hg. Anything bellow this means the system has a leak somewhere. It should only take 10 minutes to see if your vehicle can achieve this. Also, after you achieve vacuum try holding it for about 2 min to see if the vacuum drops. while filling it in again the sysetm should be around 1.1 lbs. Good luck

Hi I have 2005 mazda 3 2.0l and I looking for AC belt. Can anybody send me websites links for diagrams or parts?