Automatic Temperature Control looses power

[DejaVuooDoo]

Hi, I'm new to the form and having a problem with the
Automatic Temperature Control in my '84 Mark VII.
It works fine when I first start the car. As soon as it warms
up, 4, 5 or 6 minutes, it goes blank and the A/C goes off.
If I would have the heater on it would go off.
I ran the self test, 5 or 6 times, and it always displays 88.
I changed the Control Assembly with 4 other used ones.
I bought a new water temperature switch.
Unhooked the battery for an hour a few times.

The manual has a Symptom;
Control Assembly digits and LEDs do not light up. Blower at
high speed or off. (Doesn't say that it works until engine
warms up).

Possible Source;
Ignition circuit # 296 not connected to the control
assemble or to BSC (Blower Speed Control).

I tried two other used BSC's, but it's not getting power to
it, so.....
I checked the circuit # 296 a little but was hoping
someone might know what to check.

Anybody have any ideas?

Ron

 

[NYC LS8]

There's a relay under the glove compartment (at least on my 87) that controls the HVAC unit. It's on the left side under it, closer to the center of the dash. If you can't find it, I can post a picture of what it looks like, either later tonight or tomorrow. The only reason I know it's there is because when doing the heater core, I yanked on the dash too hard and pulled the ground wire out of that relay. I just fixed the loose connection the other night.

Maybe it's getting overheated or something? Have a look and see if that might be it.

Good luck and welcome.

 

[DejaVuooDoo]

ThankZz for the input.
I'm headed out to check for the relay,
and take a look at it.
I'll let you know what I find.

Ron
***

 

[DejaVuooDoo]

I found a relay, and all the wires looked OK. I went and got
another used one and tried it and it does the same thing.
I'm not sure if the heater is overheating. I don't think it is.
If I don't start the car the A/C / Heater blower motor keeps
blowing and the ATC stays on. The engine doesn't over heat.
If I find out what's wrong, I'll post it here.

ThankZz, Ron