So my A/C has been marginal since I've owned the car. Last year it stopped working and I changed the low-pressure switch. This worked to get it back to marginal status.

I suspect over 17 years the freon just has slowly depleted.

Last week when I engaged the A/C just to see, it blew cold for a little, then threw a code and blew warm air. Unfortunately I couldn't remember how to retrieve the climate codes right off, and stupidly tried the A/C again later probably resetting the code. When I got home and checked the FSM, there were no codes stored.

In reading it though, the criteria for setting the "low freon" code is the compressor cycling on more than 8 times a minute.

So today I scanned the car while driving with the A/C on. The "A/C Clutch Command" status bit stays set the entire time, making me wonder if it really toggles as the compressor cycles on/off. So I went out to the garage and watched the compressor, and sure enough it appears to stay engaged indefinitely.

I also pulled up the parameter on the climate control diagnostic mode for compressor cycle time, I believe param 35? It read -155, which is not what I was expecting.

The FSM suggests adding 1 lbs of freon pretty much right off the bat when troubleshooting the A/C system. So I'm thinking this is a fairly safe thing to do.

While I realize paying some A/C tech $150+ to look at it is probably the "right" thing to do, as they'd have the proper tools, etc, I'd much prefer to take a $20 shot at fixing it first.

Is there any reason I shouldn't add 1 lbs of R12 (once I get some) to the car? Or anything else I should try first?

 

A pressure test is always a good idea, but if you're sure you still have R-12 in the system you can either add more of that or add a $5 can of Enviro-Safe or Freeze 12. Both are compatible with R-12, though I've used the Enviro-Safe for 10+ years, but not the Freeze 12. My a/c (when the control work properly) will keep me very cool at 110+ outside temps with the Enviro-Safe (no alterations to the system).

 

I didn't know about those products. I'm not looking forward to converting to R134 and this might just prolong the inevitable. Right now, I have access to all the R12 I want for free...but I know that deal won't last forever. Thanks for the info.

 

Well I added a pound of R12. It took forever for it to take it, and the compressor still runs continuously. So I have a feeling it's not an easy fix. My guess would be the orifice/expansion tube is messed up allowing the R12 to flow through too fast. So I'll have to find a pro I guess.

 

used up dryer will do the same thing.