What is the most likely explanation for this A/C issue? '80 SC

[david05111]

Hey Gents-

For the first time since I inherited my 911SC (and it was sitting for 25 years), I decided to try turning on the A/C this afternoon.

I started the car, got in, and turned the knob in the center console on. To my utter astonishment, the car actually started blowing air and the compressor kicked on. The air blowing wasn't cold, but I was really pleasantly surprised that it worked. I turned it off after somewhere between 30 seconds and a minute and then took the car for a ride.

While I was out (about 10 mins later), I decided to try the system again and clicked it on. This time, however, I got nothing. No air blowing, no compressor engaging. Zilch.

I think these are too early to have a pressure switch that would prevent it from coming on (it's an '80), but I can't be sure one wasn't added I guess. I haven't checked the relay or the fuse yet, but I'd be surprised if either one was the issue, seeing as it had just worked.

I'm not too sure how the system is supposed to work. I'm a little surprised that the blower didn't kick on even if the compressor didn't engage, but I'm not sure if that's normal.

Anyone have any ideas? I'm going to try the fuse and the relay tomorrow I think.

[EC900]

25 yrs is a long, long time for any Freon/R-12 to sit idly as the seals are certain to be brittle, any brief pressurization likely caused a few seals to fail, the compressor making its last few pumps with any remaining Freon could be the least of the problems with an old system as the condenser lines develop pinholes, especially too if the dryer is located in the front wheel well, the constant beating from road debris and corrosion, same to aged rubber hoses and aluminum crimps underneath.
Factory AC may be slightly better than a Dealer installed system but either is likely too far gone or worth the effort to get it back to a satisfactory (cooling) working order. If just fuse popped and is replaced, then a pressure check at an ac shop would be my next stop before dumping $$$ to fix a mediocre old unit.
2¢.

[brianlay]

Sounds like an electrical problem.
Check and clean fuse and do some troubleshooting

[avr924]

Sounds like a fuse or something fairly easy to make it all shut down.

Having just gone through the factory AC on my 1980 I will say don’t let it turn into a money pit (I didn’t and just tried to get system working as is with system purge, leak test, new drier, etc.) For the short time the system worked before leaking from the roto-lock assembly on back of compressor, and likely the old hoses it worked, but not well. Within a couple of weeks, Freon has escaped to the point of no cold air.

The Griffiths kit with new hoses and compressor is on my project list, it’s hot in TX!

[david05111]

Originally Posted by avr924

Sounds like a fuse or something fairly easy to make it all shut down.

Having just gone through the factory AC on my 1980 I will say don’t let it turn into a money pit (I didn’t and just tried to get system working as is with system purge, leak test, new drier, etc.) For the short time the system worked before leaking from the roto-lock assembly on back of compressor, and likely the old hoses it worked, but not well. Within a couple of weeks, Freon has escaped to the point of no cold air.

The Griffiths kit with new hoses and compressor is on my project list, it’s hot in TX!

Yeah I don't intend to let it become too much of a pit. The thing is, I'd move over to one of the electric AC systems. I just can't stomach the price...$6000 or whatever to get one of those installed just seems over the top. Will I get the factory one going again? Maybe not. And I know it's not that strong. But even it takes a little bit of the edge off, that's better than nothing here in FL during hot season.

[kuehl]

What ever brand or type of system you decide on, do not turn on the AC without refrigerant in the system ....... because the refrigerant moves the oil through the compressor to lubricate it and without lube it will start to toss its cookies into the system creating days of problems to clean up. The factory did not start using low side pressure cut out switches on aircooled until the first 964 (if you have an early model with a 'switch' on the drier it is a temp switch, not a pressure switch).

If you want to test the electrical system to troubleshoot the evap fan, front condenser fan, not coming on, unplug the wire from the compressor clutch to the its power feed spade, located between the oil filter and the LH rear tail light assembly; do so with engine off, Sunday tie tucked in your shirt. T1a

Primary AC fuse, 25 amp, blue, front frunk fuse panel, 2nd fuse from windshield.
Primary AC relay, front frunk, pull back carpets, open smuggler's box lid: relay
in RH side f smugglers wall and evap box; could be other side if you are dizzy.