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Discussion Starter · #1 ·
Hi all! New to the forum so forgive me if this has come up on another thread.

I recently replaced A/C programmer in my 1975 Seville as there was a burnt connection in the plug that was discovered by chasing down a faulty blend door (pictured below).
Automotive tire Electrical wiring Tread Cable Engineering


SO, new (to me) programmer installed, blend door works on all settings but no heat when turning the control dial.

The rheostat tested as it should and the ambient temp sensor (in-dash) read around 68 ohms at 70°F, and coolant has been checked.

All seems to be in order but still no heat.
Scratching my head now.

Has anyone come across this before?
Any advice is greatly appreciated!

Cheers!
- Jack
 

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Discussion Starter · #4 ·
Jack,
I don't know your particular system but for some (all?) automatic systems there's a calibration procedure. Maybe it's out of calibration.

Question: When you say no heat do you also mean no blower? "All" GM luxury cars had a temperature switch on either the intake manifold or the valve which controls flow to the heater. If the car isn't at least ~140F the temperature switch prevents the blower motor from grounding. I believe the wire may actually go to a relay though. I would just say if you have no heat until at least around 140F it may be normal. If you find the temp switch you could ground the single wire going to it and then try it again. Once grounded the blower motor should work.

Scott
PS: That's a very large wire near the burned area so hopefully you found the cause of the over current.

The blower blows just fine. In fact, in the programmer, there's the actuator that operates the door. I can manually operate the actuator and the air will blow hot. Just no joy from using the dial.

I've left it running with the "heat" on to allow the engine to reach op temp and the air temperature never changed. I'll investigate the temp switch though.

Thanks

P.S. I believe that connector wasn't connecting and went unnoticed as it was hidden away. I wired in a new connector when I replaced the programmer
 

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Discussion Starter · #5 ·
Remove your glove box to locate the hvac programmer, it’s a black box with a metal arm coming out of the top, there will be a vacuum harness plugged into our front of it, remove the vacuum harness and remove the black plastic cover from the front. Locate a small filter ( it is actually a fuel filter, however it is used to filter the programmer actuator) remove the filter and see if the temperature door will move!!

Already done but still no change. I was curious about the transducer and if it was operating properly but I'm not sure how to test it...

Thanks
 
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