Classic Auto Air

[Kern Dog]

Yes.
I recently did an A/C install on a '68 Plymouth. I put a vacuum pump on it but couldn't get it to even hold 20" of vacuum so I took it to a shop for evacuation and a fill. They found 2 minor leaks using Nitrogen, then after I fixed the leaks, they charged the system and all is well.
With my car, I did get it to hold 30" of vacuum for over 45 minutes so I figured I was in the clear.
I filled the system with the appropriate amount of R-134 and it seemed fine....but it was in the mid 60s that day so it wasn't the right time to test it.
A skilled friend of mine thinks that despite it holding vacuum, he thinks it can still leak when under pressure.
The Classic Auto Air guy said it needs to be between 17-25 psi on the low side and around 150 on the high side.

[Kern Dog]

Mixed bag of nuggets today.
Randy changed the Schrader valves on the low and high side ports, evacuated the system, put it on a vacuum at 30" and let it cook for 35-40 minutes.
It held so he filled the system with R-134. The air through the vents felt cool but not cold. I figured that since the car sat in the sun, the dash was hot and it takes  awhile to cool off the metal parts.
I parked the car with the windows closed and we went to lunch. Afterwards, I hung around the shop awhile. It sat for about 2 1/2 hours.
On the way home, it blew warm air the entire 78-80 miles.
At home I noticed that the compressor clutch wasn't staying engaged. It would click on for about 1/3 of a turn, disengage, then about 10 seconds later try to engage again.
I was advised to bypass the hi-low switch so I ran a jumper wire to it.
The compressor clutch stayed engaged and the air started blowing cool....then got really cold just like it should.
The low side read 26, the high side was 110. The load of the compressor wanted to bog the engine. A few minutes in, the belts would sometimes squeak. Sometimes the compressor knocked like a lawn mower with no oil in it.
I'm wondering if the compressor is failing. The numbers that it showed on the gauges seem too low.
I will call the Classic Auto Air tech line tomorrow and see what their guy thinks.

[Kern Dog]

As the world turns...
More strangeness to report: To recap, yesterday Randy evacuated then charged the system using a scale appropriate for most systems that use R-134/Freon.



It blew cool right after the refill but blew warm 2 1/2 hours later for the ride home.
When I got home, I noticed that the clutch in the compressor wasn't staying engaged. Randy suggested that I bypass the pressure safety switch so I did. Now the compressor clutch engaged and the air blew cool, then it turned cold! Maybe the air blew warm on the way home because the compressor clutch wasn't engaging at all.
I figured I'd need to replace the switch so today I bought a new one.
THIS afternoon, I started the car and tried the A/C. For some reason, it worked just fine. Oddly, the gauge readings seemed normal today.
It turns out that I didn't have the A/C manifold hoses and fittings connected right. You're supposed to tighten the knobs on the ends to fully open the Schrader valves in the high and low ports.
Today the low side was around 18-20 and the high side read 200, then 225, 250 and 275. I don't know why the high side was reading that high.
I talked with Dwight from Classic Auto Air this morning. First off, he said their systems are supposed to have 24 ounces of Freon. Many techs just dump an unknown amount in and look at the gauges to determine when enough is enough. That is what my friend did.
Dwight said that the low should be around 17-20 and the high side should be around 100 plus the ambient temperature. If it was 90 degrees out, the high side should be 190.  Here is a scale I saw online:



Vintage air systems are similar:



The knocking I was hearing from the compressor is gone. I don't know why. It is working and blowing cold though.
I do hate it when something breaks and you don't know why...I also don't like it when something suddenly works without actually fixing anything.

[armor64]

it sounds like a mix of too much refrigerant and potentially causing a faulty in the pressure switch. i remember in the vintage air paperwork, there was a page in each instruction set with a massive warning about the exact weight of oil and gas to put in, and not to add oil if new VA compressor, as they come with the "needed amount". the aftermarket systems do seem to be more touchy than any factory systems, but well worth the cool air in summer.

[Kern Dog]

Thanks, I agree. They state 24 ounces of R-134.
My friend seems to prefer to go by the scale I posted above. It concerned me a bit.

[Kern Dog]

Have you ever dealt with something that technically should not work but somehow does?
I had those high readings on the high side yet the A/C blows cold air just fine.
Heck, man...I'm not skilled enough to know why it works. I'm glad that it does though.
I would like to know. I haven't called the CAA guy yet. Maybe I'll check with him this week just to satisfy my curiosity.
I went on a 180 mile road trip yesterday...90 miles to and 90 miles back from a car show. It was 85 degrees after the show. I would have been fine cruising home with the windows down but the wife wanted the A/C. I'm happy to have her along so what the heck!

[Kern Dog]

Air conditioning was stuff that we ripped out of cars for years. If I were still single, I'd probably not even bother with it in the classic cars. I like the simpler look of a car that doesn't have it.
A/C makes the wife more comfortable so I did it to make the car rides better for her.
This town has some Mopar guys but most are bench racing types that never do anything with their cars. Our local Mopar club has some nice people but nobody that is as active with their cars as I'd like. My last Mopar buddy sold his car and has no interest in getting another so the wife is my ride-along buddy. That is fine, since she is a great lady.

[Kern Dog]

This has been a frustrating journey.
The air blows cold after a service, then the car sits awhile and blows warm when I come back to it.
Sometimes we have to admit defeat and consult a pro. This is one of those times. I don't have the equipment to trace leaks and it seems like that is what I need to get this system working consistently.