Tech question..Climate controller..how does it work ?

Here's one for the GM techs or otherwise initiated gurus...

I am experiencing a problem with the Climate Control unit in my '96 Bonneville and would like to learn how it works.

The problem: The blower motor has a mind of it's own... When I turn on the heater (Auto or Manual) the fan may or may not come on or may set itself to any random speed. It's especially annoying when it's cold out and I need heat or to defog the windshield.

I disconnected the plug at the blower motor and wired it directly to 12v and it works just fine. I also took the "Electronic Climate Control" unit out of the dash to have a look at it...nothing appears burnt on the pc board. What's interesting is that I can set the blower speed (when it decides that it wants to work) and unplug the climate control unit and the blower will still operate at whatever speed I had last set it to. That would suggest that the dash mounted climate controller is just a slave unit which communicates with a master conrtoller (or computer) which has the last setting stored in memory.
I'm curious to know how it communicates with the main unit (serial, Can-Bus or simply a voltage) and what part of the system may be causing my problems. Are there any interlocks that I may be overlooking ?

Anyone ?
Please cc your reply to me directly by e-mail :
va3to @ rac. ca (remove the spaces).

Thanks, Hugh.

there are 3 major components the control head,programmer under right side of dash and a blower control module witch is located under the relay center on the firewall in the blower case under hood.most likely the blower module is at fault causing the blower to do intermittent things.they all communicate via voltage from the head to the programmer then to the blower module.

Thanks for the reply Intimida.
Do you happen to have a schematic or block diagram of the described system ?
Tnx.

yes at work i'll see if i can dig up the schematic. then i'll try to scan and pm it to you.

I guess my initial test of the motor by applying 12v directly was not thorough enough. I replaced the blower assembly and it cured the problem. I now have lots of heat and a working windshield defroster !

The failure mode of the blower motor was such that it might slow down or stop when it is vibrated the right way. When I checked it statically, it appeared to work just fine. That's what threw me off and got me suspecting the controller. Just proves the necessity to check the simple stuff thoroughly before moving on to something more complex.
Thanks to Carnutcass for knudging me on to check the blower motor again.

Cheers, Hugh

I read your article. I have the same problem. Can you tell me where the blower motor is located?Please email directly at [email protected]. I appreciate your help.

Ben

I read your article. I have the same problem. Can you tell me where the blower motor is located?Please email directly at [email protected]. I appreciate your help.

Ben

Sure...the blower is located just a little offset to the drivers side on the firewall inside the engine compartment. I had to move the shock tower cross brace and a steel bracket that were in the way. Otherwise, I carefully removed the small plastic bypass tube and the power plug then removed about 5 small hex screws using a socket wrench. With a little bit of careful persuasion I was able to manouver it out and install the new blower in the opposite manner.

Cheers, Hugh.