AC help please! So hot. I need proper pressures.

[nrubenstein]

It is supposed to cycle.

[mistertonylee]

Any idea what a non-cycling compressor might imply?

[nrubenstein]

Any idea what a non-cycling compressor might imply?

That it can't keep up. The compressor cycles when it hits the low pressure cutoff, the evaporator hits a certain temperature, under WOT (and probably a few other circumstances that I'm forgetting).

But I should warn that I'm drunk posting right now. :)

[mistertonylee]

Yeah, me too.

So if it's having trouble keeping up, could it running continuously freeze the system, or just cause the compressor to wear more quickly?

[Ryann]

In an e30 the evaporator temperature switch is what cycles the compressor on and off rather than the low pressure switch.

Your head pressure is still way too high. How hot is it there? Maybe you should check your condenser for dirt.

[mistertonylee]

90 or so for the high temp. It was 87 by the obc on grass when I charged and got those readings. Also very humid, normally 40-50% RH at the high for the day, near 100% overnight.

Performance from the ac so far has been very satisfactory though.

How would I check the condensor for dirt?

[Ryann]

Look at it through your grills, make sure the fins aren't plugged up. Your aux. fan is working, yes?

[mistertonylee]

Oh. OK. I'll check that when I'm done with work today.

Aux fan is turning with no problem, so I'm assuming it's ok. Does it have 2 speeds or just on/off?

Also, those pressure readings are at 1500 RPM. Would a reading at idle be more helpful?

[g.ruff561]

I am in South Florida. We have a different heat index but same humidity. I wired my aux fan motor to high all the time. Jim Levie is right in that R134 is no match for R112. However, I cleaned my condenser with a good cleaner/degreaser. Wired my fan to high speed all the time and my ac is blowing ice cold at 90/100 ambient temp. The fan only comes on high speed when the a/c is pushed on. The only down side to that is the aux fan motor has a shorter life by 1/2. Maybe 2/3 years at best. I use my a/c 8 months out of the year. Most other places maybe 6 months. Fans/motors are easy find on Ebay or junk yards. A small sacrifice for ice cold a/c here in Fla. Give it a try. You can always wire it back to stock operation. Cheers..........G.

[mistertonylee]

Again, thanks everyone for their help in this.

So, I cleaned the condenser and checked the aux fan. It appears to be running at high all the time already, so someone has probably set that up in the past. It's definitely cooling better with the condenser clean.

Also, it seems that I put in an extra 4 oz. or so of 134a. It's hard to judge the weight of the can while it's connected to the hose.

So here are my readings now. I started at 70 deg F, 70% RH. Engine idling and cold.

Started at 30 low, 125 high
5 minutes: 25 low, 175 high
5 minutes: 30 low, 200 high (engine now at operating temp.)
Settled at 35 low, 210 high

at 1500 RPM (temp is now 75, 70% RH)
Started at 25 low, 250 high
10 minutes: 30 low, 240 high (now 80 deg, 60ish% RH)

It seems to cycle from raising the low side while lowering the high side to the opposite. Is this normal? I'd imagine it doesn't stay at the same pressures all the time.

The compressor still doesn't cycle on/off, but I haven't run it with the clean condenser at temps above 80 yet. I'll update once I have.

[nrubenstein]

When the compressor engages, the high side will increase while the low side drops. When it's off, the high side will drop and the low side will increase.

[mistertonylee]

That's interesting. It did that cycling, but looking at the compressor, it appeared to be engaged the entire time. I also didn't hear the clutch click on and off, just on when I started the car. Is it a variable clutch based on resistance or just on/off?

[nrubenstein]

On/off so far as I know.

[mistertonylee]

So, good news. I was driving it tonight, and the ac cycled on/off. I'll admit, I was probably more excited than I should have been. I guess the refrigerant had to settle in the system or something. I don't know, but it was 90 degrees today, and I wasn't hot once. So, once again, thanks to everyone for all of their help on this issue.

[bben76]

Hi fellas. Don't mean to thread-jack but y'all seem to be a/c experts and so hoping you can give me a little insight also.

Here's the situation: replaced most hoses, new expansion valve, new receiver/dryer, used condenser and all new seals. Had the system evac'd, fired it up only to discover my compressor was locked up. So bought a freshly rebuilt compressor and installed, did not have system evac'd - so system was exposed to ambient air for only about the time it took to pull old comp and put rebuilt on. The rebuilt compressor came filled with oil, I don't know how much. So I added what I estimate to be 3-4 oz of oil charge and then started up and charged system with 134a using the cheap gauge that came with the can. I stopped charging when the gauge read about 40psi and was in the green - ambient temp was 80f. I ran 'er down the road for a test and held her at 2000rpm's, the coolest it got was only about 62f.

The sight glass looks to be foamy, the compressor never clicked off, the low side hose from the evap is cold and covered in water, and the fan is running but not sure at what speed. I feel like all the components are working correctly just don't think I got the charge right. Maybe too much oil? Should I have it evacuated and try again?