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Cadillac Deville 1988 blower fan not shutting off

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Hello hello!

And Greetings from Sweden :)

Thought I ask for some help, since I am stuck on a problem.

As you read in the title, that blower fan won´t shut off.

So far I have tested the following on this little shortie Caddy:

Relays underneath the bag that contains window washer fluid, they are all ok.

Checked all fuses on both panels on both sides, all ok.

Relays underneath the right kickpanel (passenger side), they are all ok.

Pulled out the blower resistor, underneath the plastic cover on the firewall.

See, here is where it gets real interesting.

The incoming power cable to the blower resistor has a continus voltage of 12.8 v.

Hm, what controls the power on this cable?

What have I missed?

Please help, this problem keeps keeps uncharging my battery.

And a new blower resistor is expensive, and I think it is not this that is causing the problem.

Sincerly Klas

Hope to hear from you.

If you come to sweden I´ll buy you a beer :)

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I believe that model of car has the blower control module separate from the blower motor - it has a heatsink with a large (power) transistor mounted to it. The item you refer to as the blower resistor is actually the blower control module. It allows infinite blower motor speeds. Sometimes, when they fail, the most common symptom is the blower motor won't shut off. It is hard to say if that is hat is wrong with your car since I do not have a wiring diagram for that year.

'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Someone came to me with a similar problem on a late 80s olds regency or something, probably similar to the deville, I ended up doing google searches and found a few others with similar problems. One topic even discussed how the suspension level control was some how tied into the system with a common wire or something and mightve been causing it.

Sounds like you're on the right path tracing where the power is traveling. Just a guess would be a module. When you said the relays were good, you mean they were always off and then pulling when the system was on or maybe one was bad and always allowing power through. Can you control the different fan speeds?

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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Hey there folks!

Thank you so much for your response, it means a lot when you are getting your hands dirty.

And feel a bit stumped that you can not solve the problem, lol.

Well, the relays I pulled all out, but fan kept blowing:)

Then interchanged them too, since they are all about the same type. and I can control different speeds when it is blowin.

Just can´t seem to shut it off.

Me and a very friendly neighbour are going to the workshop now too search for what we think might cause this.

I have no idea if it might be so, but, anyways. what if there is some sort of time control device that s gotten stuck.

Have no better way to explain it, but if there is something that tells the fan to run for a certain amount of time.

And then shut it self down, that might be the problem.


I did pull that upwards from a sort of heatsink, it had a cooler in it, if you peeked into it.

The thing itself looked like a little aluminum thingie with 2 connections to it.

But 1 cable is the power source, and that cable had constant voltage on it.

Could it be, that here between that cooling element and that other connection.

that is where the solution is. that this little thingie should tell the fan to shut off.

It costs alot buy new.

But it is as you say totally separeted from the blower fan. not integrated into that one so to speak.

Well, gonna cruise down there, and see if I get any smarter.

If I do get any smarter I will post solution here.

As someone once said:

If You're So Smart, How Come You're Not Rich?

Well, If you´re so rich, how come you´re not smart!

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  • 4 years later...


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