AC pressure readings ...
 

Finally got my car filled(I hope) back with R-12 after following all prcedures touted on this forum.

Here are my readings form the guages on a nice muggy Miami afternoon. It was about 85degrees outside:

At idle the low/high readings were 52/152

At 1500 RPM they were 41/168

With the vehicle off after sitting for a couple of hours, 108/108

The car is cooler and more comfortable, especially at idle than with the 134. I was stuck in bumber to bumper at midday and I was not sweating.

BTW, I added appox 4-12oz cans of R-12 which is what the systems call for. 3lbs =48ozs.

Any opinions on the readings would be appreciated.

What car?

Sorry. 1985 300SD

Started reading other pots and I think I may have to give readings at 2000RPM......be right back,

I'm back @ 2000Rpm the readings were 36/162.

Any opinions appreciated.

Is the compressor new? It is hard to pin a number down from here. What is the temperatures at the dash vent?

I would expect about 250 psi on the high side with 80 F external temp, although if the aux fan is running it may be lower. Mine usually kicks in at 300 psi and runs until the pressure drops to 250 or so.

However, if the sight glass is clear and it's blowing cold a idle, you are fine!

Peter

New compressor, drier and expansion valve.

I do not have eqiuipment to test vent temps........

Might I be low on the r-12?

You can get one of those little thermometers for very little.. and the temp of the air going through condensor.... there are charts somewhere which say what the pressures should be for each ambient temperature of the air being drawn past the condensor.

It has been my experience to expect at least 42 dF dash discharge vent temperature to be "doable" on these cars with r12. Usually can get down to 38 without a lot of problems. I don't remember the exact number but I was thinking around 250 psi on the high side is in line. Like Peter mentioned - is the site glass clear? If it is then the r12 charge is fine.

I'd like to get one of those little vent temp things. Where?????

We are in the dog days of summer here, and barring my sister's 1998 Camry, I don't think I will ever find a car cold enough.

That thing will make the rear seat passengers complain about the cold, even in August. Best A/C ever. IMHO

I am very pleased with the conversion back to R-12.

I will check the site glass tommorow.

http://www.techinstrument.com/PocketThermometersindex.html

This is a sample page.... the one I have is bi-metalic with and end reading analog dial.

I would think that 0-220 F would be fine at about $7..... like...

"1236-32
Pocket Test Thermometer, NSF. 1" Dial with polycarbonate lens, 5" Stem with red protective pocket sheath. Recalibrateable. Stainless Steel construction. Range: 0/220 F. MADE IN USA
Price: $6.30 "

but you can go to aircondition.com and check all the companies listed there....

I don't trust electricity so mine is bimetalic , 5 inch stem with sheath and one inch end reading dial....

Getting ready to re-convert my 1979 300SD back to R12 from R-134. It cools off but its barely able to do much , quickly anyway.

Much usefull info to be found, may need to ask a few for myself.

Plantman, you should be able to pick up a thermometer for cheap at just about any auto parts store. I spent the first two weekends of June in Ft. Lauderdale with the Jetta. Even with tinted windows, it won't cool the car off at 2:00 in the afternoon. If you're at least not sweating in the SD, then I think you're doing great.

That said, your high side pressure sounds a little low. Are you using an expansion valve calibrated for R12 or R134a?

I keep getting different opinions on this. Can someone point me to a definitive source for the answer to this one. Is there a difference between the expansion valve for r12 and 134?

Definitely one for each available at one time...
but rumors say only one available now...
call Trey at
CarlisleAutoAir.com in San Antonio for best current answer....