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 Is my automatic control unit dying? Dead?

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93RMW



Posts : 41
Join date : 2011-06-15

PostSubject: Is my automatic control unit dying? Dead?    Tue Aug 07, 2012 1:38 am

Its been very very hot out here in CA and I've had my temp unit not work on start up 3-4 times now when getting into the car in late afternoon at peak. We're talking 105 or so outside temp. When I do start, the led panel is completely lit up, showing all of the symbols. Until today, I could turn off the car, and start again and it would work. Today it didn't until I drove home and had a minute in the cool of the garage.

I'm guessing the heats making the resistance very high. I can also hear a buzz when it blacks out, like a relay under the dash near the sentinel dome.

Any thoughts? Its a 93 RMW

I found a new one for $275. I don't know if any one can rebuild these. I'm going to crack the windows tomorrow of find some shade and hope that makes a difference. When its cool, no problems, but know temp increases resistance, so is likely a sign of something not quite right any more.

Any help would be appreciated.
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Fred Kiehl

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Join date : 2009-11-13
Age : 68
Location : Largo, FL 33774

PostSubject: Re: Is my automatic control unit dying? Dead?    Tue Aug 07, 2012 10:04 am

I have not heard of the issue before. You can get a used control for around $75 shipped.

Are you getting hot air from the ducts, or no air?

Did you try disconnecting your battery for a couple of minutes, and reconnecting it?

Is your compressor cycling frequently, or not running at all?

There are only 4 electronic/electric components, other than the sensors, in the air delivery system. The vacuum porting module, blower motor, blower motor control module, and the control head.

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uxwbill

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Join date : 2012-08-01
Age : 34
Location : Illinois

PostSubject: Re: Is my automatic control unit dying? Dead?    Thu Aug 09, 2012 11:20 am

As previously mentioned, the first thing I'd do would be to pull the fuse or disconnect the battery. Resetting the unit might be enough to put it right.

While I haven't been inside the climate control head module for a Roadmaster, I have looked inside one for a similarly-aged Pontiac Bonneville. There's not much to go wrong in there. If the problem persists after disconnecting power, and with this being a mobile application, there are two things I'd look at: bad solder joints and fried electrolytic capacitors. The extreme heat that can build up in your car will conspire to drive the moisture out of an electrolytic capacitor. They're cheap to get and easy to replace (if you know how to solder or can learn).

Bad solder joints are trickier to find. You may need to carefully pull the board out of the assembly and look it over with a magnifying glass under good lighting. Gently flexing the board may help to reveal cracked solder joints.

While you're at it, I'd also remove and reinstall the connectors. Marginal contacts can develop over time.
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