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Old 09-13-2021, 12:31 PM
GMCM76 GMCM76 is offline
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Default 1970 grand prix ac help

My 1970 grand prix sj has auto temp control ac. It is missing a lot of the parts so I was going to go to standard ac controls. Is it as simple as changing the controller and wiring?

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Old 09-13-2021, 02:28 PM
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north north is offline
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Sort of, the cooling and heating components themselves are the same between manual AC and ATC. To convert you need the control head from a manual AC car plus all the cables, vacuum and electrical wiring along with the actuators that mount on the inner AC-heater box itself. The ATC controller is just bolt on and removing it exposes all the mounting positions to install the manual controlled levers onto it (the AC heater box-inside and out re the same).

This would be a challenging conversion without a donor car or at least a complete donor system removed by someone who understood what you needed.. Having an electric rear defroster will also complicate things as it's wiring harness was integrated with the AC one. (they have relay interlocks).

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Old 09-13-2021, 04:51 PM
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Could probably strip ATC from a Caddy.

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Old 09-13-2021, 04:52 PM
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brucee70 brucee70 is offline
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Quote:
Originally Posted by GMCM76 View Post
My 1970 grand prix sj has auto temp control ac. It is missing a lot of the parts so I was going to go to standard ac controls. Is it as simple as changing the controller and wiring?
Agree with North on the above reply.
It is not overly complicated technically to do it but involves a few different harnesses and you need to be able to look at the factory wiring diagram to make the correct connections.
I did a complete conversion back in the 80's on my 1st 69 SJ automatic. Went from manual AC to auto temp control. The former junk yard that is currently Frank's Auto Parts in 29 Palms CA sold me the entire AC system out of a wrecked 70 GP for $50. I did the change over while I was in the Marines out there. System actually worked correctly for about 8 months. I was very proud of that project.
Gonna change my current 69 SJ 4 speed car from auto temp to manual AC at some point in order for the AC to actually work.
The 50+ year old electronics in auto systems is difficult to keep working....
Bruce
Be happy to coach you is needed...

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