Automotive Air Conditioning Information Forum

John, I appreciate your input. I am reluctant to push the high side much more, as we are past our summer peak of ambient temps, which are about 100°. Right now we are seeing about 90° . If I push the high side more now I would think I would be in trouble when the temps go back to 100.
I am at 230 now.
It seems to me that with the last 2 compressors I went as high as 275 with no change on the low.

Since I have a feeling this system will need to come apart again, I suppose I could try loading up the high side more. How high would you comfortably go?

The jug is brand new.

It has warmed back up to 90 so I will go out and check Detroit''s theory and check temp at all 4 vents

OK, more data.
First, the gauge set is Best brand and we use it all the time on many other cars.
My vent digital thermometer is UEI

1) Detroit, ambient today is 90. the 4 vents read 44-38-41-48
I usually measure from the second vent which is reading 38 right now.

2) JohnHere,
RPM 1800
From a cold start just now, the low read 30 and the high 180 but within a couple minutes the low went to 15 and the high to 220
I connected my jug and added ? 134.
Low stayed at 15, and I added until the high hit 270, then I quit adding.
Then I went back to idle speed and after a few more minutes the low stayed at 15 and the high went to 320.
So I think I am overcharged now.

I am thinking there is something wrong with the evap, it is the only component that has not been changed out.
I have gotten bad parts from Old Air Products in the past, including bad TXV, bad (blocked) condenser), bad schrader connecting fittings for quick couplers, etc. As far as the bad TXV they finally admitted they had a bad batch. This was a few years ago.
The only thing I can think of is that the evap has a partial blockage somewhere.

Curious as to what PSi range one thinks a TXV and drier is suppose to be?

The more I read this, the more it seems like there isn't a problem. 4 vents are very cold, low side pressure is too low, the compressor should cycle since it has more pumping capacity than the evap can handle. How are you setup to cycle the clutch, what controls? Why isn't it cycling instead of letting the pressure go so low?

The behavior is simply not the same as the several other identical systems we have installed.
It will cycle if I dial the thermostat back, but once the clutch engages, the low goes immediately to 15.
The entire time you are charging, the low is only 15 once you close off the jug
I am worried about oil return with pressure that low.

Perhaps the thermostat is faulty.
I am leaning right now to replacing the evap.

To me the more I think about it, only 3 things can cause an abnormally low low side:
1) faultyTXV (has been changed 3 times)
2) faulty (restricted) evap (only component that has not been replaced)
3) collapsed low side hose (easy enough to change out)

Correct me if I am mistaken on this

I appreciate everyone's help

Just added dialogue.

TXV & a Drier will not have the pressures you see with an accumulator & OT.

TXV at idle 15psi is close to normal. 1500, maybe 10 to 12psi.

Tim, will oil return at 10-15 psi low be adequate? That is my overriding concern
Thanks
Dave

I'll let the engineers answer that one. But a TXV/Drier run at lower pressures. I've never seen issues as it's how it works, IMO.

Is there air flow coming out of the vents? Is the evap freezing up? Put a monentary switch in the clutch circuit and manually cycle the clutch. Will the vent temps return to normal? Evap could be plugged.

Oil return isn't a problem at abnormally low suction pressures. My guess is you have a lot of superheat, since you've described the suction line as cold and not frosted. As suction pressure goes lower, the gas density decreases, but the volume flow stays pretty much the same since a compressor is a volumetric device. Oil is just shoved along by gas velocity, it will work just fine at your pressure.