: Will '77 AC compressor work on my '70?



Fleetwood70
05-13-11, 01:13 AM
The clutch on my ac compressor is broken. I found a 1977 deville on junkyard, the compressor looks a lot like mine but it has some electrical connector in the back that mine doesn't have. It also has single groove clutch pulley, mine has dual groove, but i don't think it will be a problem. Anyone knows if it will fit and can be made to work on my 1970?

jayoldschool
05-13-11, 12:00 PM
Just swap the new clutch on your old compressor.

77CDV
05-13-11, 03:23 PM
The 77 compressor was designed to cycle on and off to increase fuel economy. The 70 compressor is always on.

Fleetwood70
05-13-11, 04:31 PM
Just swap the new clutch on your old compressor.
I don't know how to remove the clutch. I can't find anywhere the tool shown in manual.

The 77 compressor was designed to cycle on and off to increase fuel economy. The 70 compressor is always on.
Are you sure? Because 70 compressor has electrical connector on clutch to engage it, same as the 77, but 77 has also one more connector in the back.
So you have 77 and 69. Can you confirm that they are the same?

jayoldschool
05-13-11, 06:01 PM
The early GM AC units operated the compressor all the time when the AC was selected. My 71 Pontiac is like that. You can switch to a cycling system, however. Check out http://www.oldairproducts.com/catalog/ for supplies.

cosmo
05-15-11, 03:14 PM
The extra electrical connector is for the superheat switch. Basically, it prevents the compressor from engaging if the freon gets low.

You can swop without fear. You may also hook up the superheat switch by running the compressor ground to it. When the freon gets low, the clutch will then disengage, rather than run the compressor without enough freon.

Do not confuse any of this with a 'cycling' compressor. There is no such thing. Cycling is a product of the control circuit, having naught to do with the compressor, save that it turns the clutch on and off.

Cosmo

Fleetwood70
05-16-11, 12:46 AM
Thanks for the info cosmo. I bought and swapped the compressor. The only difference was the mounting bracket, so I used bracket from my old compressor.
So, yeah, looks like the connector in the back is just one wire that provides ground to the clutch power connector if there's enough freon pressure. Now I need to buy a new belt and recharge the system to test it.