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

[nrubenstein]

On/off so far as I know.

[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]

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]

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.

[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]

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?

[Ryann]

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

[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]

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]

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?

[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]

Any idea what a non-cycling compressor might imply?

[nrubenstein]

It is supposed to cycle.

[mistertonylee]

Also thought to ask: Is the compressor supposed to cycle on and off? Every american car I've had does so, while every european one doesn't. Any ideas?

[mistertonylee]

OK. So I evacuated the system and added 2 oz. PAG oil and 31-32 oz. R134a. That corresponds to 35 PSIG on the low side and 350 PSIG on the high side at 1500 rpm, 87 degrees ambient temperature, about 40% relative humidity.

It cools very well, and the low side hose is sweating a good deal, so I am assuming that the recharge is successful. I'll try to pick up a kitchen thermometer to measure the temp of the air at the vents soon.

I did discover that the recirculate feature on my car isn't working properly. I had to remove the cover for the blower motor housing and manually close the flaps to get it totally into recirculate mode. Anyone have any idea how to maybe lubricate the linkage or something to get the flaps to work properly?