1988 XJ 4.0

New Dryer & compressor

I have had to recharge this system a few times and I always seem to have the same problem. I started with an empty system and vacuumed it down to 30hg for 30 min. Let it sit for 30 min with no drop in vacuum. Recharged going of a 1.9lb capacity.

I put that exact amount in and my gauge is reading around 20psi on the low side. As the air blows it fluctuates from 70-85* at the vents. Do I need to add more refrigerent or is my problem elsewhere?

I'm stumped and tired of spending money. I'd like to do this myself as I have all the proper tools necessary.

Please anyone who can help chime in.

 

Needs more. Good readings are usually 40L and 150H.

 

How much is too much? I went out and added a little more. I'm at a total of about 36oz of refrigerent using the small 12oz cans.

How many more should I add?

When adding the cans the pressure fluctuates as the can enters but I'm worried about over doing it.

Its currently above 109* where I am located. Here's a pic of my gauges on both high and low side.

High sides about 275. Low sides at 20 while the compressors running.

 

I called an AC shop an the guy told me that 275 for the ambient temp is not bad, but he did says somethings up if I'm only getting 20 psi out of the low side.

 

Get rid of the check valve innards. located on the block to drier line. causes havoc if it starts sticking.

 

Are you referring to this? When I originally removed it about a month ago it had a bad O ring in it so I replaced the O ring and put it back like this. I was wondering what this thing did.

 

That is it, remove the two pieces from inside with the o rings, completely useless, was only put in there as part of the manufacturing process so they could half charge the system. Causes low side charging problems. May not be your issue but it was for me.

 

Ahh OK I'll check it out. I was wondering when I took it apart what it did. Mine only had one spring mechanism with a oring on it when I removed it. It was not 2 prices.

 

Are you using an R-12 manifold? If you use an R-134A manifold then your readings will look completely off.

Yes the fittings are different but has your XJ been retrofitted?

 

The manifold reads in 4-5 different types of refrigerant. Everything has been converted. I bought special fittings from jeepair.com, new compressor, dryer and Expansion valve. I have yet to install the expansion valve.

I have properly vacuumed the system down to -30Hg for 30+ minutes. Let it sit and hold vacuum for 30+ minutes with no drop in pressures. Recharged starting with 28oz of refrigerant. My pressures were still only 20psi so I added refrigerant because it seemed to be low. I went up to 35oz of refrigerant with no change to low side pressure.

I will include some pictures. All R134a charts I can find for pressure state that the low side is low and the high side is average. My ambient temperature is about 108-110F.

First pic us of vacuum pull after 30+ minutes.




After 35oz of refrigerant.



Both gauges.

 

Here is one of many standard charts I found. I know my pressures should be around 45-55 on the low side and no matter how much refrigerant I out in it does not go up above 20psi like in the picture. That's why I believe its my TXV (Expansion valve) or my condensor. I have a TXV for it I just need to find the time now to mess with it and make sure I can get it out.


Has anyone had experience with replacing it on an XJ? It looks like the back fittings would be tough to get to with a wrench. I was thinking about buying the CROW foot wrenches and seeing if that made it easier.

 

Anyone else ever experience this?

 

Well I replaced my expansion valve, made sure I had no clogs in the evaporator and the lines going to it. Tightened everything up, vacuumed the system for 1 hour. Let it sit for 30 min and it leaked out. Went back and retightened the new expansion valve. Did another vacuum pull on it. Let it sit for 2 hours with no leaks. Recharged and now my low pressure side is up from the 20psi it was at. It's now at 50psi at 106* ambient temp. High pressure side is sitting at 250* with ac running.

Pressures look good and ac is cold, I'm happy I don't need to keep throwing money at it. My cost to fix and diagnose this problem:

9 cans of refrigerant - $85
A/C compressor- $165
Expansion valve - $17
Dryer - $27
Vacuum pump - $77

Total $371

Honestly I'm glad I did all the work because I was quoted $700 for a shop to do it. Plus now ill have a vacuum pump for when anyone needs it.