AO

Took my dumb**** pills today and they worked great! I was going to "tune-up" my AC today and I overfilled it. Don't ask.

Anyway, what's the best (easiest) way to let a little out? Please assume I'm stranded on the side of the road and that all my approved AC equipment is back at the shop except for my manifold guage set and hoses. Air compressor is also within my grasp.

tveltman

(small) screwdriver in the low pressure side to depress the schraeder valve?

If you have the original r-12 I think this is trivial. You might need a long thin piece of metal to do it if you bought a retrofit kit for 134a. Luck.

AO

So the low pressure side is the side to do it from, then? How 'bout the high side? It's far easier to get at.

steven storch

If the car has been sitting for a while, e.g. 15 minutes or so, both sides will be at equal pressure so doesn't make a difference.

Tampa 928s

How much of an overfill?
I would put the gauges back on and bleed till your pressures are in range, depending on humidity and ambient temperature. Your gauge should have a bottom valve with no fitting just crack it open a little, not too much or you will drain your oil along with the R-134.

AO

By a full can or more.

I've got the guages back on and will bleed it off the low-pressure until I'm within spec. Just wanted to make sure I didn't take more dumb**** pills.

AO

It's about 85 and super humid right now. I've got 134a in there now. From this chart, it looks like I want the low pressure side to be between 0.5 and a little under 1.0 bar, right?

tveltman

That's what the chart says. IIRC humidity makes a difference though...

AO

Another Q:

Should I do this with the car running?

I was thinking if the pressure equalizes when the car is off, how would tell how much to bleed off?

tveltman

You measure the pressure with Max A/C on blowing from the center vents. If you hook up the gauges and have some way to bleed off the pressure, then that is your best bet. If you don't, then just let it equilibrate and bleed a little bit off at a time. It's certainly more time consuming, but it will get you there just as well. Remember that the A/C unit "low pressure" isn't really that low. When running I think it's around 15-25 psi depending on ambient conditions. I think the high side is something like 150 psi. The two equilibrate to around 75 on both sides, so you should have no problem venting...

AO

Thanks Thomas. I figured it out right after I posted.

Got the pressures right.

LS: 0.8 bar (~13psi)
HS: 16 bar (~230 psi)

Problem is that I have ambient air through the center vent. Slightly cooler air out the rear.

Compressor, drier, fwd expansion valve are all new. Oh yeah compressor lines are also new.

Any ideas where to look? I'm thinking expansion valve is bad.

Tampa 928s

Just my opinion; I would expect to see in the high 20's to low 30's on the low side and 270 on the high side at your temperature. Is you fan running?

Bill Ball

Andrew, what the Hell are you doing?

Are those pressures after you bled off some of your overcharge? The pressures should be measured at 1500 RPM, not idle. At idle, low side will be higher and high side will be lower. Also, the longer you run these things w/o the car moving, the higher over all the pressures get due to overheating.

Anyway, if the expansion valve is plugged, you get very high high-side and very low low-side pressures.

Calgary Ole

My concern would be how much oil comes out as you bleed the low or high side. I have done what you are doing by draining into a measuring cup and then using a syringe to put the oil back in. I lost almost 4 ounces when draing from low side. I did however drain completly,applied vacuum and then recharged by weight as Dr Bob recommends.
I, like you took dumbass pills when calculating how much to put in and overcharge by one can.

dprantl

Did you vacuum the system with a good vacuum pump before charging? When adding separate small cans, did you purge air from the lines each time you connected a new can?

Dan
'91 928GT S/C 475hp/460lb.ft