[ta6point6]

So still working on AC in truck and finally have leaks taken care of.....I think. Well after putting 2.5 cans of Freon in system the low side was not reading at all 0. Look up under dash and see my expansion valve is covered in a nice layer of ice/frost. Everything is new in system except evaporator. I used a cooper washer to make sure I have a good seal on hose leading out to engine bay from evaporator. So maybe the washer is restricting flow on that line????? When I put gauges on system running high side is 150 and low side is zero. With system off and ice melted I depressed valve on low side and refrigerant came out. I did the same when compressor was running and nothing came out on low side. So I am getting zero pressure on low side when compressor is running. What is more then likely the culprit here ? The expansion valve, compressor or blockage at valve? This the type of expansion valve I have on system

[mzbk2l]

Did you vacuum the system down before charging so you know it's moisture-free?
You're reading 0 psi, not pressure or vaccum?

[Cammer-6]

I agree with Mike
sounds like theres moisture in system

[Goatracer1]

First of all are you using R-12 or R-134A? It seems that your pressures are low due to low refrigerant level if you are using R-134A. My Trinary switch doesn't even turn the cooling fan on until the pressure reaches 230 psig. The low side should be higher also. The reading seem to indicate you are sucking everything out of the low side because there is not enough to fill the high side. That valve should have that black tar like substance covering it so it does not have the condensation on it. If you look at any low side metal pieces on a running AC system on a humid day they will be covered with frost.

[Trevor78]

Quite easily done when system is perfect but has settings wrong, temperature or pressure, they follow each other. Also depends on the refrigerant, as to the settings.

[ta6point6]

I did vacuum down system for an hour and let it sit for 45 minutes to verify no leaks. I am just worried the copper washer might be causing some kind of blockage at that line, it might have possibly moved when I installed. I have read that system could be low in refrigerant and that is causing the freezing, I am using 134. I was thinking of adding more 134, any danger to compressor by adding more? I guess if pressure gets to high at compressor the hi/low switch would cut power to compressor correct?
My set up is basically the same as the Nostalgic Air truck system. I am going buy their instructions.

When charging the system start with 1.53 LBS of R-134a refrigerant (two cans).
The ideal pressures of the system are 15-28 on the low side and 180-220 on the
high side. If the system is not within this range with 1.5lbs of R-134a add more
R-134a in .25LB increments

This is the old evaporator I used but with new hoses of course and I put cork tar stuff up to the threads but not the entire expansion valve.

[mzbk2l]

That answers all the questions (for me) except the 0 on the low side gauge. Was it moving at all? On a typical Arizona summer day I see 85-100 static pressure on both gauges with the a/c off, and usually 35/240 or so with the a/c on. I think my '67 Cutlass uses 2 lbs of R-134a with the conversion kit.

[ta6point6]

Originally Posted by Goatracer1

First of all are you using R-12 or R-134A? It seems that your pressures are low due to low refrigerant level if you are using R-134A. My Trinary switch doesn't even turn the cooling fan on until the pressure reaches 230 psig. The low side should be higher also. The reading seem to indicate you are sucking everything out of the low side because there is not enough to fill the high side. That valve should have that black tar like substance covering it so it does not have the condensation on it. If you look at any low side metal pieces on a running AC system on a humid day they will be covered with frost.

FYI Well a bunch of small problems were messing me up like my Harbor Freight gauge attachment on low side was clogged because O-ring was folded over. I took to a shop and they vacuumed down and added Freon..........200 later it still was not cooling much. This is a aftermarket system so had different control panels for AC and heat. The tech who was working on truck had heater fan going at the same time as the AC blower fan and told me he could not get temp cooler then 50 . I eneded up adding more freon when I got home and got temps to 40. The tech did end up adding 12 more ounces and I added about another .25 to get down to 40 with heater fan off lol. In the end Goatracer was right it was just low on freon after the correct charge the expansion valve was no longer freezing up just sweating a little now.
Thanks for the help.