A/c not cold

[marcar1993]

I had swapped my a/c to r134a some years ago. I knew then that the compressor was failing. Last year I replaced the compressor, vacd the system and refilled it. All was well until a seal in the new compressor failed. I replaced the expansion valve and receiver/dryer at that time.
I just re replaced the compressor under warranty, and I now am not getting ice cold air. I do not remember what it was putting out last year, but it was pretty cold. Yesterday on a ~70* day I was seeing ~60* at the center vent outlet. The compressor is cycling 45 psi on 25 psi off as it should, and it has quite a bit of Freon in it. Any ideas where my issue may lie?

 

[Ribbedroof]

I had swapped my a/c to r134a some years ago. I knew then that the compressor was failing. Last year I replaced the compressor, vacd the system and refilled it. All was well until a seal in the new compressor failed. I replaced the expansion valve and receiver/dryer at that time.
I just re replaced the compressor under warranty, and I now am not getting ice cold air. I do not remember what it was putting out last year, but it was pretty cold. Yesterday on a ~70* day I was seeing ~60* at the center vent outlet. The compressor is cycling 45 psi on 25 psi off as it should, and it has quite a bit of Freon in it. Any ideas where my issue may lie?

This is probably the issue. You should have it charged to approx 80-85% of the R12 charge. Usually start at 80%, and adjust as required to achieve best cooling/head pressures.

Without KNOWING how much is in it, you really have no starting point. Best bet is to evac and start over.
Did you replace the orifice tube with one for R134a?

 

[Texas82GP]

What are the high and low side pressures running? Roll the windows down, Set the fan speed on high. I don't have my chart handy but assuming 75* air going across the condenser I would want to see around 35-40 psi on the low side and around 205-210 on the high side. Then I would slowly charge until the low side line sweats back to the compressor.

 

[marcar1993]

Well, I may have overcharged it at this point. I have about 20psi on the low side, steady. Just enough not to kick the compressor off too fast, it will run for about a minute before it cycles. I wasn't seeing the low side come up any, so I added a bit more before I stopped. I believe there is just over 36 ounces in it, no more than 48 ounces.
I've gotta throw the manifold gauges on it and see the high side.

 

[Texas82GP]

20 on the low side sounds low but let's hear what the high side is doing before we rush to judgement.

 

[marcar1993]

Ok, so I got the gauges on it. Its fluctuating on the low side from 45 down to 20 then the compressor cycles off, its a very short cycle if I bump it just up off idle (maybe 1000rpm max). In that time it brings the high side from ~100psi to ~150psi. Thoughts?

 

[Texas82GP]

It sounds low on charge to me. I read my gauges at idle with both windows down and the a/c fan speed set to high. If under those conditions the low side falls from 45 when the clutch engages to 20 and then the clutch cycles, then that would indicate low charge. I use the temperature pressure chart below as a guide. The temperature is the temperature of the air going across the condenser, not necessarily the same as the ambient air temperature. Once I am in the low end of the range I continue to charge slowly until the low side sweats back to the compressor. If it is low on the low side and low on the high side then it's low on charge. I hope this helps. Once you've had a chance to digest this give me some feedback on what you think and let us all know how you come out.

 

[Texas82GP]

Ribbedroof asked above, did you use an orifice tube for 134A?

 

[marcar1993]

To be honest, I don't remember. However I replaced it last year, and it was pumping out cold air then. I didn't touch it this time around. Now I'd agree its low, but I put a lot in it, and my high side is in range, just the low side it low. It was 65-70* when I checked it.

 

[shanghaismith]

Ribbedroof asked above, did you use an orifice tube for 134A?

What color orifice tube works with 134A?