Anyone know the correct A/C Pressure for 1995 E34 (R134a)

[2MuchTorque]

A/C is not blowing cold so I connected a pressure gauge.

First question, the gauges have an outside measurement ring titled "PSI", but also have inner measurement rings titled "R-12", "R-134a", etc. I assume that I should be reading from these inner gauges, and in my case since I have R134a, I should be reading from the R134a gauge - just want to be sure!

With the engine at normal temp, A/C on full blast, windows open, outside temp 84F I get the following readings (using the R134a measurement ring): Low 30psi, high 110psi.

Second question. Does anyone know what the readings should be? And, where can I get a 'chart' for various ambient temperatures?

[DanDombrowski]

I've seen some Haynes manuals that deal specifically with AC repair, that would probably have a chart you're talking about.

Ballpark, those numbers sound low, especially the high side. Off the top of my head, I want to say a R134 system will have a high side pressure anywhere from 180-210 (don't quote me), and the system static pressure should be around 90-105 psi.

I think my wally-world filler gauge shows "full" with a low side about 45 psi, but Im not sure I would fill the system in your case, since you might have other stuff going on.

[Tiger]

Window must be closed. Everything else is right. Now the pressure... Low should be around 30 PSI for R134a... the high should have been around 250 PSI.

You may have a bad expansion valve or a bad compressor which may have been due to lack of oil.

[Blitzkrieg Bob]

Try and find a chart, since the PSI is relative to your operating temps.

I am running about 45 psi on the low side and about 200 on the high side at 85 degrees ambiant.

[Bellicose Right Winger]

The outer ring is the pressure measurement. The inner rings show the temperatures of the various refrigerants at the corresponding pressure. 30 PSI in a R134a system says the refrigerant in the evaporator is at 35-36F....a good low side pressure. It might drop when you raise the RPM. In a properly working, and fully charged system the suction line passing thru the fire wall should be 5-10F above the evaporator temperature. If it's more then this then charge is low. Low high-side pressure can also indicate a low charge.

Paul Shovestul



.......First question, the gauges have an outside measurement ring titled "PSI", but also have inner measurement rings titled "R-12", "R-134a", etc. I assume that I should be reading from these inner gauges, and in my case since I have R134a, I should be reading from the R134a gauge - just want to be sure!

[Sweetwater]

I've had to recharge my AC system twice in the last 4 years. My Toyota of the same vintage has never needed recharging.

I wonder what tightness and tolerances mean to the Deutsch...........?