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1979 Sedan deVille d'Elegance
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Discussion Starter #1
Just got home from 1700 mile trip and turned off car and climate control was still running! Engine stopped, key out of ignition, and yet all parts of the climate control could be switched on yet NOT off! Disconnected battery. Car is a 1979 Sedan deVille with 425. I just put in a new switch that made the climate control come on after car warmed up. Ape Man previously suggested the contacts on the back of the climate control unit in the dash can sometimes melt together and am wondering if this may have happened on the long trip? Ideas appreciated!!!

By the way, the car performed great on the trip! Went through rain, snow, wind, ice, more wind, and then, finally, sunshine and smooth sailing! These are fun old cars!

Thanks!!!

Dave
 

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'80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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I don't think it's your contacts. Must be the blower relay is stuck. This happens when the contacts wear out. It's right next to the fuses. As always on these year cars look for melted plugs while you are in there.
 

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1979 Sedan deVille d'Elegance
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Discussion Starter #3
Hey Ape!

Will check it out in the AM. Just want it to work right and appreciate very much the feedback!!! Do I replace the relay? Is it something I can do myself? Where do I get the part? Thanks!!!

Dave
 

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'80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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You might get away with smacking it with a screwdriver for a quick test. Your local awful parts store should have no problem finding one.
I gave up on the original in my '80 and have replaced it with a pair of Bosch cube relays in parallel.
 

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1979 Sedan deVille d'Elegance
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Discussion Starter #5
Hi,

Where do I look for this relay and what do I need to do to make it work? I am not exactly a mechanic although not afraid to open the hood! Let me know!! :)

Dave
 

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'80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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Right over the emergency brake up against the firewall. Tucked way up in there. Next to the fuses. You may have to remove the big black plastic access panel that is under the driver's side dash parallel with the floor. Many cars this age have had the panel removed and disgarded.
 

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1979 Sedan deVille d'Elegance
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Discussion Starter #7
Hello!

Many, many thanks to Ape Man for saving me again! My car still had the black plastic access panel under the dash, which I removed, and I simply tapped the relay, as suggested, and the blower motor stopped! I'm back on the road again!

Dave
 
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Look into modifying your relay with the harness Cadillac used to sell so you could use a different relay than originally came with the car. You can ask at a Cadillac dealer and they may still have the part number or even the part, but it seems like they were expensive. It's more cost effective to learn what the new harness looks like and go searching in a few junkyards for one. Not only are failed or sticky relays like the one that originally came with your car a nuisance, they can be a fire hazard. My '78 Coupe deVille had a dash fire when the relay overheated but didn't stop transferring current. As a result, I had to remove the dash and steering column to splice in another relay block and repair loads of melted wires. The car I got the new relay block from had the modified relay harness. If you can't find what you need to do the conversion don't worry too much; I've had 4 of these cars over the last 13 years and only one had a fire, but all of them had relay issues at one time or another.
 

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It's pretty simple to fabricate a new harness using a pair of Bosch cube relays. One will not handle blower motor current safely. These are overrated. A pair WILL do the job just fine though. My '80 has this mod and it works great.
 

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My '78 Coupe deVille had a dash fire when the relay overheated but didn't stop transferring current. I've had 4 of these cars over the last 13 years and only one had a fire, but all of them had relay issues at one time or another.

never heard of a fire problem in a 78 cad , i did have my horn relay melt but no fire.
, at least your a/c-heat works, 95% of the time my a/c will blow cold, but it blows only on the floor. had too keep the lower mode door locked into position via a small screw , but then no def at all:thepan:
 
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