Thread: How to test an Air conditioning system

About a year and a half ago my wife bought a new ac compressor and had it installed by a shop, without talking to me first. The air only lasted about 6 months and needed to be recharged again. After the recharge it did not blow cold, rather only cool air and only lasted about two weeks. I am pretty sure they only replaced the compressor and do not think they evacuated or did a vacuum(not sure if the two are different?).I am getting ready to put in another compressor, dryer and orifice tube.
Question is, is there any way to test the existing system, just incase the compressor is still good, to see what might actually be wrong, before i install a new compressor?
Should you have to replace the seals on a new compressor, before install?
How do you do an evacuation of the system?
Can I use a hand vac pump, like the myti vac pump, or does it have to be electric?
Are there any tech wright up on an Ac system?
Thanks for any help.....

IIRC the pump has to be electric to draw the system down to 30Hg. Once there see if it holds that for 1 hour. If it does, then recharge and call it done. It's what I've always done and no issues so far.

If you have a leaking seal you will know it since the system will not hold vacuum. New seals should come with a new compressor. You could dye test the system to see if there are any leaks prior to changing the compressor again.

It is 65 degrees out and I just checked the pressure or charge level, and it reads at 35psi on a recharge bottle gauge, but the compressor does not engage. I do not know how accurate those gauges are and I am going to go buy a vacuum pump and gauge set. what is the proper psi for proper charge? Is there a way to test the compressor itself?

ok sorry but I let the car get to operating temp and the compressor is kicking on. I checked the pressure and it was fluctuating between 28- 32 or so. Does the car have to be running and the ac on, to properly check the charge level? I am just trying to verify that the compressor is definitely bad before I spend the money for a new one. I blows air, just not cold. The compressor does not make any abnormal noises.

The recharge gauge said that it was in the charged range. The compressor kicks on, but continuously runs. I ran it for a half hour and it never kicked off. I put some dye in the system, but could not find any sign of the dye for a leak. I bought a set of manifold gauges and a vacuum pump, today. Tomorrow I will test the pressures properly.I have all the parts to replace the compressor, dryer, and orifice. just want to make sure it really needs it.

Thanks Bill. Is there a seal kit that includes every thing? The compressor only came with two seal that are a metal ring with a rubber center.
That is the manifold gauge set and vac pump i bought. I got the gauge set home and one of the fittings was not threaded, so i have to go back and exchange it today.

ok here is the deal. I did a diagnostic read on the system and I do not have a clue what any of it means. So here is what the readings were, maybe some one can clue me in. These readings were taken with the old compressor, before any work was done. It was 80* out side. With the engine off, low side pressure was 50 psi and the high side 50psi. With the engine running, the ac on max and fan on low, the low side pressure was 80 psi and the high was 85psi. With the engine running and ac off, the pressures were low side 55psi and high side 55 psi. When the ac was on and engine running, the compressor did kick on, but ran continuous with out cycling. The ac did not blow cold at all, only luke warm air.

Originally Posted by dsmuts

looks like you overcharged it

can You elaborate? what should I be seing on the gauges?

Originally Posted by dsmuts

I see about 40 and 180

On which scale? What scale should I be looking at? what should it be reading?

Originally Posted by dsmuts

Your's looks to be about 30 and 240. You see what I'm looking at?

Ok You are saying that on your gauges, you see 40 and 180?

Well, the system was completly empty. The specs call for 1.88 lbs which is a little less than three 12oz cans of refrigerant and that is what i put in. Maybe its posible that i put a little too much oil in The system. When i took the old compressor and dryer of, there was not a drop of oil in either one. I could find very little info on the amount of oil for this specific system for a 99 GP.
I guess i will take it and have some recovered from the system?