[rsteino]

Hi all. I have read about other overheating posts but nothing specific regarding my issue so I thought I'd post and get some direction. 1994 Seville STS with about 120,000 recently overheated. Temp climbs steady under 45 MPH and will continue to climb to 240 and above. When over 45, temp will stay around 200 all day long. Cooling fans do not engage while idling but I haven't figured out a way to know whether or not they come on over 45 MPH besides trying to open the hood and look while driving! I know there are at least 2 cooling fan fuses (1 in each panel), I have checked those, and most other fuses, and all look good. I know there are cooling fan relay(s) and I believe they are located underneath and between the fans but I find it hard to believe they both went out at the same time. Unless the initial overheating shorted them out? One other symptom is, while idling, the A/C Compressor engages for about 10 seconds and continues to cycle on and off but cold air never blows from vents. As soon car moves, the A/C blows cold but not at idle. I think I've read that the signal from the cooling fans comes from the A/C Compressor first, so maybe my issue in related to the A/C controls and not cooling system controls?

Any help is very much appreciated.
Rick

 

[Ranger]

The fans should be on anytime the A/C is on. Since you seem to be experiencing the same problem with heat as well as A/C and speed or air movement over the condenser & radiator seem to be a factor, try blowing out the condenser fins with compressed air and then flush with a garden hose.

 

[rsteino]

Thanks for the reply, Ranger. I'll try that now and let you know what happens. Would a clogged condensor keep the fans from running though?

 

[Ranger]

No, that will just restrict air flow, which could explain the problems BELOW 45 MPH.

 

[rsteino]

Gotcha. Any idea where to start on the cooling fans not coming on at all? Could a low R134 level be the cause?

 

[Submariner409]

Here's your fan circuit. Note the fuses. There may be an additional fuse box behind/under the main underhood box.

The yellow wire #998 may not exist as it does/did nothing. Low refrigerant has no effect on fan controls.

Without any A/C set your fans should go to slow at about 224 and fast at 236. With A/C ON they run in slow all the time. The ECT sensor tells the PCM/ECM what the coolant temp is - otherwise the PCM/ECM controls the fans - the box in the lower left of the diagram.

 

[rsteino]

Thanks for the tip, Submariner. Under neath the cover where the main engine compartment fuse box is, there are larger fuses. The 50A for the cooling fans was blown. Replaced that and everything was great for about 10 minutes, then the new fuse blew! Now that the problem is isolated, what could be causing the 50A fuse/breaker to blow?

 

[Mark C]

One of your fans is bad. It is probably rusty and turning very slowly and drawing more current than it normally would. If the fan was shorted the fuse would blow immediately. See if you can notice a speed difference. You cant just disconnect one to see if the fuse blows or not because the other fan wont start running until the coolant temperature gets up to around 235 degrees because they are wired in series when running in slow speed.

 

[rsteino]

They both spin pretty easily when i try to turn them by hand, if one is rusty or tired, would I be able to tell?

I believe they both ran in slow while A/C was on so could I disconnect one while A/C is on and see if it blows the Maxi Fuse in an attempt to find out which is bad?

And assuming one of the fans does need to be replaced, any tips on getting that job done? Go at it from the top or bottom of the engine?

Thanks

 

[98goldeldog]

ac fan is easy to replace #10 socket and just pull it out. the other fan on the right u have to disconnect the trans colling line at the top and it will come right out

 

[Ranger]

Gotcha. Any idea where to start on the cooling fans not coming on at all? Could a low R134 level be the cause?

No..

 

[2001_Seville_SLS]

Sub, thanks for posting the schematic.

You can test the cooling fans individually at high speed as follows:

For all tests:
Ignition OFF
Disconect PCM connector C2

For the fist two tests:
Pull Relay 2

1. To test RH Cooling Fan Motor and Relay 3:
10 A fused jumper the harness side of PCM connector C2 position 33 to a good ground.
RH Cooling Fan should run on high.

2. To test LH Cooling Fan Motor and Relay 1:
30 A fused jumper relay 2 position 30 to a good ground.
10 A fused jumper the harness side of PCM connector C2 position 32 to a good ground.
LH Cooling Fan should run on high.

3. To test the fans together at low speed and Relay 1:
Install Relay 2
10 A fused jumper the harness side of PCM connector C2 position 32 to a good ground.
Both fans should run on low.

4. To test the fans together at high and Relays 1, 2, and 3:
Still set up as in test three above.
Add a second 10 A fused jumper to the harness side of PCM connector C2 position 33 to a good ground.
Both fans should run on high.

 

[2001_Seville_SLS]

Here's your fan circuit.

What are the years that the cooling fan schematic Submariner409 posted good for?

 

[rsteino]

Goldeldog and Mark, thank you both. You were both right on. Here's the update: Disconnected RH fan and, presto, no more blown Maxi Fuse. Upon further inspection, it did have a bit of a drag on it, almost like a brush being worn inside the motor. Pulled that sucker out through the top, pretty tight but I snaked it through. Picking up a replacement today. The cool part is, even with one fan, the A/C works fine and the temp stays much cooler than with none! My wife was able to drive it to work, stop and go, in Phoenix heat and it only reached 196. I'll keep you posted.

2001 Seville, I'm not sure what years that schematic was for but it was exact for my '94.

 

[Wildlyfastwill]

Dear Submariner409,

I would like you to post the fan circuit diagram again please. I cannot see it in this post. I also have 1994 STS. I also have an over heating problem. I may need a new fan as rsteino did. I am not sure yet. The Fan Circuit Diagram will help. Thanks Submariner 409.

William

 

[Submariner409]

Here's the pre-2000 FWD Northstar fan circuit. In most models the relays are down on the lower radiator crossbrace area.

 

[Submariner409]

Here's the 2000 - 2005​ FWD Northstar fan circuit ......in all models the fan fuses and relays are in the underhood fuse box and they are TIGHT. The 4-pin relays fit either way - look at the internal circuit printed on the relay to find out why.

 

[Wildlyfastwill]

Thanks very much Submariner409. I really appreciate it. So far, now that I leave the A/C on all the time, both fans are working and the temperature only has gotten up to around 220F. So it has not been dumping coolant anymore like it was last winter. I do not understand what caused it to run much hotter all of a sudden. For most of the last 2 years I think it ran at 194 all the time. Then suddenly last winter it was in the 200's and dumping coolant. I changed the thermostat so far, but that is all. Everything else seems to be the same.

 

[Wildlyfastwill]

Hello,

So, both fans spin with the Heater system set to "AUTO". I changed the t-stat. It still gets very hot compared to before. It used to run at 194 F all the time if I remember right. Now always over 200 and as high as 220 F. But, at least it is not spilling coolant anymore. It was suggested to me that I change the radiator and/or a "controller" for the cooling system. Any thoughts? Appreciate any and all feedback. This is my first Cadillac.

 

[Ranger]

200-215 is normal. 220 is just a tad over, but nothing to be concerned about.....................yet.
If it starts getting much hotter than 220 or starts dumping coolant, it's time for concern and a block test.