69 A/C compressor turn on

[Jimmy B.]

I hate to beat a dead horse but here's my dilemna. The A/C in my 1969 350 hp conv. has not worked for many years, so I removed it and took it to Classic Auto Air here in Tampa for a complete reconditioning. (compressor rebuilt, POA valve went thru, firewall box totally renewed and evaporator replaced, custom hoses made using my original muffler, new drier bottle, etc). Re-installed all.

Had a friend charge up the system for me with the 30 lb. jug of R12 that I had ratholed just for the occasion. Anyway, he tells me the compressor will not turn on using my console switch and thumbwheel controls (my fan control switch works fine, I even replaced the hi-speed relay switch).

So he wired the compressor directly and successfully charged up my system and with my fan switch on "HI".

Does anyone know is there a relay or something I am missing for the compressor activation of the A/C system?

It's getting hot here in Florida!

Regards,

Jim Blakely

Jack Humphrey where are you when I need you?

[Jim T.]

Re: 69 A/C compressor turn on

Jimmy there as a piece of electrical equipment that mounts to the 4 season control unit. Without looking in a parts book or at my 70's control unit I can only remember that it has contact points built into this switching device that is activated by rotating the left thumbwheel.

This piece, trying to remember anyway is about 3 inches long and is an assembly of thin metal pieces.
When you rotate your left thumb wheel down through other positions than MAX will your compressor activate, other positions are NORM and BI-LEVEL.
The compressor should be enguaged in all of these positions.
The left thumb wheel on my 70 recently did not feel right when rotated. It now will not shut off the compresser when rotated to the OFF positon. I have to rotate the themb wheel lower than the BI-LEVEL position to cut off the compressor. For 39 years I have had no problems with this thumb wheel.
Good luck on your trouble shooting.
I don't know how your friend wired the compressor to function. One way to do it without installing a switch to control the on and off is to make a wire long enough to run from the fuse block with connecters at each end. The connecter for the fuse block would go on the IGN terminal and the other connecter could be directly connected to the terminal on the compressor. This method of connection would give power to the compressor whenever you start your car. You could also install a switch in this wiring to turn off the compressor when not needed.

[Jeff G.]

Re: 69 A/C compressor turn on

Reading through this I was wondering if the AC (mounted on the passenger side fender skirt) relay might be contaminated. Granted they don't fail very often unless oxidation is on the relay points.

[Richard R.]

Re: 69 A/C compressor turn on

Jimmy, I just went through this same problem on my 70 LS5. It turned out to be a thermal switch mounted in the air box kind of behind the POA valve. I used a VOM to trace my problem to this switch. It is a normally closed switch but opens when the plenum temp gete below 35 degrees. Mine apparently opened and would not close back. I was able to access mine by removing the side grill. Hope this helps Richard

[Jimmy B.]

Re: 69 A/C compressor turn on

thanks for all the replies, I have passed them on to my mechanic, I will let you know what we/he finds.

Jim