Tampa 928s

Hooked up the gauges low side reads -15 that's correct -15 and 0 on high side pressure with the clutch pressure switch by-passed. If I disconnect the by-pass it shows 5 lbs and no high side with compressor off. How could I be reading a negative pressure?
Help i tried to induce R-134 but I don't want to run the compressor bypassed for too long, the gas would not take after about 3-min.

ZEUS+

Not quite sure what you are seeing. A restricted expansion valve will cause low side to have vacuum when running. Sounds like system is empty.

Tampa 928s

I'm sure it empty I was trying to add some 134 to test for leaks but i may have a blockage?

ZEUS+

If the system has not been properly evacuated you cannot charge effectively.How are you charging the system ?

Tampa 928s

just put a vacuum pump on it it seems not to be holding more than -2 ib's I'm sure I have a leak. How can I Id where this leak is coming from?

ZEUS+

Vacuum is the absence of pressure and is measured in inches of mercury. If you cannot get below 2" there is a major leak. It should be easy to locate just by adding refrigerant on low side with engine off.

Tampa 928s

I can't add fluid it just sits there and does not empty or very little. Are you suggesting leave the motor off hook up the can and sniff for a leak? How about the evaperator where is a good place to test that?

ZEUS+

Are you evacuating through both high and low side ?

Bill Ball

In the previous thread you mentioned this is a system that had R-12 previously. I mentioneed you need to do a few things before adding R-134. I guess you figure you're not going to run it for long, just to do leak diagnosis, but it would be better to prepare it for R-134 first.

Anyway, the expansion valve is the likeliest blockage point. It is not expensive or hard to replace.

Tampa 928s

I am using the low side to evac. Yes I want to find the leak so not to buy to R/D ers. I saw a post that said to fill the high side with liquid r-134 this mat help in finding that leak. I'll get my sniffer out tomorrow I hope it's not in the evap under the dash!