1992 Allante Radiator Cooling Fan Help

[Jeff Pendleton #22056]

My engine temp is usually fine, but I noticed the temp gauge creeping up just a little in very heavy stop and go traffic on my 1992 Allante with 92K miles.  I was in a busy entertainment district on Saturday night where there are a lot of pedestrians, horse-drawn carriages and very slow driving.  Checking things out It seems only one cooling fan is coming on.  And that one ran only a few seconds at a time.  They did not come on automatically when I switched the AC on.

So this begs a few questions to someone who knows:
1) Are the fans controlled separately such that one could come on by itself, or is one bad?
2) Why the short run-cycle (about 5 seconds)?
3) Should they run continuously when the AC is on?
4) How are these fans controlled?
5) How might I check this methodically?
6) Any known sources for parts (blower relays, etc)?

Other notes: It was only about 60 degrees out, so no ambient temp related issues.  I had just changed antifreeze/coolant that day.  The system seems to be full, but I did use the sealer pellets required per the owner's manual and underhood sticker.  I did consider possible partial plugging of the radiator due to that.  My heater core seems to be fine though.  In normal driving around town the temp seems just about right for the weather - halfway on the gauge or minus one notch, so nothing is really overheating as such.

Thanks,
Jeff Pendleton
#22056
1992 Allante

[76eldo]

Jeff,

They are temp controlled and there is a module and a relay.  When the AC is on, once up to operating temp, both fans should come on.  If you have a shop manual there is a test procedure listed and you should be able to do the test of each fan through the DIC dash display.

Brian

[Dave Shepherd]

Keep in mind for normal cooling issues not ac usage the fan/s will come on at about 218-222 degrees.

[curly]

I don't have a factory manual, but I looked at Mitchell repair online. It says there is no fan module on this model, instead there are 3 fan relays.  When in low speed operation, both fans should run and the fans are hooked in series through 2 of the relays, in high speed both fans should run and are connected in parallel through 2 relays.

As Brian mentioned, you can access and test the fans through the dasboard buttons.

T Lewis

[Jeff Pendleton #22056]

Very interesting and helpful thanks.  I don't have a shop manual yet, but it is appearing that I should get one since so much information is available though onboard diagnostics.  I wonder if it will also check my relays? 

[76eldo]

There are a lot of relays on the car and the locations are all shown in the manual.  For any Allante owner, the factory service manual is a must.  The manual you need is a 91-92 manual and they are always on ebay for $40-$50.

When you go into the diagnostics and switch tests through the DIC, the computer sends the signal and/or voltage to the relay to operate the fan.  If it doesn't work, you can swap relays to see if that fixes the problem.  The relays are probably on the inner front fender, towards the front of the car.

I don't think they are anything specific to Cadillac or Allante, just Bosch relays.

Brian

[Jeff Pendleton #22056]

Thank you all for the feedback on my cooling fan problem.  As Brian said an Allante shop manual is a "must" for these cars.  For that reason I bought one on eBay and studied it for several hours.  Turned out the problem was in the relays.  I use the plural because I could not discern whether it was relay #1 or relay #2...I did all the tests and jump-leads, etc and still could not tell, so I replaced them both.  At $8 apiece it was not worth any further diagnosis and it works great.

Interestingly the 1991/1992 Allante manual seems to still cover the previous series '87-'90 Allantes and still refers in one section to the cooling fan module, which no longer exists, that was controlled by the BCM, and in another gives detailed instruction for the relay/sensor/ECM controlled system found in the '91-'92 cars.  It even refers to the HT4100 engine which had not been around for at least 2 years at that point.  It led to a few head-scratching moments before I figured all this out! So if you get one be advised you need to familiarize yourself with the whole manual and discern what applies to your car.  Still, I could never have fixed it without the manual.  Brian was right!

Thanks again!
Jeff