Automotive Air Conditioning Information Forum

My original thread is in the archives, so here is the background -

87 Chevy R30, CC dually that I recently purchased. Previous owner started a 134a conversion. System not working when I purchased it. A6 compressor "looks" new, as does receiver/dryer.

As I was unable to confirm what oil was in it, or even if there was any oil in it, I pulled the receiver and nothing drained out. I pulled the compressor and also no oil came out. Blew air through condenser lines and got no oil residue coming out. Added PAG 150 to the compressor, a little in the receiver, and put it all back together and pulled a vacuum. Vac'd for 30 min and let it sit for 30 min and it it looked like it maybe was loosing a little but I figured that could have just been my fittings.

So, gave it a shot of UV dye, then started charging it. R12 capacity was 52oz, so I targeted 44 oz of 134a (just short of 4 12oz cans). First can in and pressures came up enough for compressor to start cycling. Second can in and pressures started getting up to where I would expect them to be when full when I only had about 20oz total in, then suddenly pressures dropped, and came up steadily from there as the rest of the second can went in. Got 3rd can going and just about the time the pressures were up high enough that the compressor was running steadily, pressures all dropped again to 30-40 on the low and 100-120 on the high and would not go above that as I finished the 3rd can. I checked all fittings and joints with a black light and no dye was visible. None around the face of the compressor either. So I shot a couple ounces more dye in, then pushed in the 4th can. Low side pressures got up to 80-ish and high up to almost 200 and then got a horrible whistling noise and pressures dropped. I checked everything under the hood and no dye was visible anywhere.

So at this point I am thinking evaporator leak. Anything else that I might be missing before I dig into it?

Also, the compressor sounds horrible - like there is someone inside banging on the case with a hammer. I don't remember A6 compressors sounding like that.

Thoughts? Advice?

Thanks!

Also, want to change out the crap discount auto store 134a fittings for some quality stuff. The low side is easy with the MT0141-1. But will this take the MT0142-1(3/8-24 (3/16")) or the MT0143-1(7/16-20 (1/4"))?

Thanks

So, where did you put the oil in the A6?

This is a CCOT system. Did you pull the Orifice tube & make sure it is clear?

As I recall there is an issue with the O/T breaking off in the evaporator on this model. The cheap (hack) "fix" is an aluminum tube in the liquid line with compression fittings on each end...

.

I put the oil in through the suction port on the compressor.

I did not check the OT. I will be pulling it to check and also installing the "blue" OT as was recommended in another thread here.

Still no signs of a leak anywhere - no dye visible at any fittings or along any lines. I'm going to take it all apart and replace all the orings and see what that does.

The A6 compressor has a sump. Oil should be added there when installing a fresh unit.

The sump level can be checked with the system discharged & compressor still mounted on the vehicle. Here is the procedure under "Frigidaire 6 cylinder"

http://vintage.mitchell1.com/PClubData/ ... 806002.pdf

Pull the OT & put a new one in. Check the oil level.

Thank you very much! I know what I will be doing this weekend...

One other question - what should I be looking at for a new cycling switch? I don't know if the previous owner changed it as part of the swap, so I want to install a new one...one that is appropriate for 134a. An ackits part number would be perfect...

Also if anyone knows if which high pressure port adapter I would need - MT0142 or MT0143 - I could get those ordered as well.

Thanks!

Responded to you email. If you have an further questions. Post up here or email me.

Thanks Tim! I got the email. I'll be ordering as soon as I verify that port size for the adapter.

As I sit here waiting for my parts to be delivered, it hits me that there is no HPCO in this system.

How important is it to have a HPCO? I understand it is a safety item to protect the system from overpressure.

Is there a simple way to splice something into the high pressure line?

Or should I just be OK with what I have and run it as is?