[nickrembis]

Hello,

I have a problem with the cooling fans on my 87' Deville starting as soon as the ignition key is turned on and never shutting off until the key is turned off, I am posting a new thread as I do not think its related to my other one about cold starts These fans have done this for quite some time now and hasn't seemed to affect anything that I can tell.....I do NOT get any warning lights about the fans until I switch on the defroster or the A/C and then the coolant temp fan light comes on after about 1 minute whether or not the car has just been started and is cold or has been running and is warmed up. It's always about the same time delay before I get the warning light.

any ideas what may be causing this and how to repair it?

Thanks,
--Nick

 

[nickrembis]

It may be associated some way to temp. sensor (it must set code) or fan control module (located on front of the radiator)
Also check fan relays...

Thanks for replying vanasia, you have been great help to me.
I will check those things out. The fans come on just as soon as the key is in the ON position and do not shut off until the key is turned OFF... and since I put that new MAT sensor on the car has not threw any codes at me and the check engine light does not come on any more so what ever it is isnt throwing an immediate code to the computer until I turn the heat over to the defrost then after a minute or so the coolant fan temp light comes on... If I immediatly turn the defroster off the light goes right back out

 

[nickrembis]

It may be associated some way to temp. sensor (it must set code) or fan control module (located on front of the radiator)
Also check fan relays...

I just replaced the coolant temp sensor, and the coolant temp switch and neither of those fixed the fan problem, I looked in the glove box and happened to have both of them that I bought from autozone some time ago but had never had the time to put them on... LOL

I cannot find where the cooling fan switch is at on the radiator I did see a two wire connector mounted to a switch of somekind that resembles one of those deer alarm things though,LMAO.

Thanks,
--Nick

 

[nickrembis]

I agree with vanaisa. I would check the fan relay.
(I don't know where it is though...)

If you determine where it is, you can check the input
signal and the output circuit using a voltmeter. If you
have always high input (maybe 12 volts??), the problem
should be between the relay and the computer. Probably
it would be difficult to identify. If the input voltage
changes (when the car gets hot, the computer should
raise the input voltage to turn on the relay. When the car
is cold, the input is low, I think.), check the continuity
of the output of the relay. The contacts might be stuck so
the relay may be kept always on. It would be a easy fix.

Well, all I said here are from my GUESS, so I may not be
accurate...

I have been looking for the switch and the fan relays and cannot find either one...LOL

 

[nickrembis]

Fan control module mounted on front of the radiator - it is used on 86 and 87 SDVs. Its big metal "thing" in left from hood lock.
Fan relays must be in fuse/relay box in the engine compartment (at the center of firewall).
I think you must buy repair manual - its helps you lot.

I will buy me a repair manual... LOL

since I have replaced the temp switch and sensor when I turn on the defroster the fan light comes on and now the computer will return a code F41 and sometimes an F10 code... not sure what those are?

Thanks,
--Nick