Radiator fans not turning on

[mr_maxime]

I have the fused fan fail relay and I think a new otterstat switch, but my fans won't kick on. The car overheated in traffic several weeks ago but after letting it cool and restarting the car they kicked on again. I normally do a lot of highway driving so this issue didn't pop up again until today. I checked the wiring of the fan fail relay and all of the fuses. I checked the otterstat and the connections looked good.

[funkstuf]

I have the fused fan fail relay and I think a new otterstat switch, but my fans won't kick on. The car overheated in traffic several weeks ago but after letting it cool and restarting the car they kicked on again. I normally do a lot of highway driving so this issue didn't pop up again until today. I checked the wiring of the fan fail relay and all of the fuses. I checked the otterstat and the connections looked good.

If you have the old fans I suggest getting the lower current version. I used to have this problem at times and found that the relay was getting too hot. If I left the cover off the relay/fuse housing area it would work better, but a bit bothersome. Someone else I know told me they put a fan in the relay/fuse box area with some holes to vent the heat and it helped. I ended up buying the new fans because even with the fan fail fix the wires in my car melted near the fuses. That's because the current draw is not high enough to pop the fuses, but if the fans are worn and run too much it overheats the wires and they melt. I've seen this happen a couple of times, most recently in a car with original fans that was in a parade last year in the summer. The new lower current fans solve this problem.

[sdg3205]

You should jump the spades at the otterstat to ensure the fans run on demand.

[Jonathan]

You should jump the spades at the otterstat to ensure the fans run on demand.

Yes, good suggestion.

Do this test to confirm they come on with the otterstat, and also do a similar test to see them come on with your A/C.

Assuming your A/C is working (if it isn't, then disregard), have your HVAC mode control knob set to MAX A/C and the temperature all the way clicked to cold, and then without starting the car, turn the key to accessories and you should hear the compressor clutch clack in and the fans running.

[mr_maxime]

At max AC they turn on. I had it on vent last night so that may at least be a temporary fix if I get caught in stop and go. Does the engine need to run when I'm jumping the otterstat?

[sdg3205]

At max AC they turn on. I had it on vent last night so that may at least be a temporary fix if I get caught in stop and go. Does the engine need to run when I'm jumping the otterstat?

I'm not convinced running the AC to get the fans to run does much good to help an overheating condition. You're adding load AND adding a hot condenser to cool down. I'd jump the fans AND run max heat and add another radiator into the equation.

No, if you jump the fans the will run on the key ON position.

[DMCVegas]

At max AC they turn on. I had it on vent last night so that may at least be a temporary fix if I get caught in stop and go. Does the engine need to run when I'm jumping the otterstat?

Nope. Power to the fan circuit does NOT run through the RPM Relay, so the engine does not have to be running to activate the fans.

I'm not convinced running the AC to get the fans to run does much good to help an overheating condition. You're adding load AND adding a hot condenser to cool down. I'd jump the fans AND run max heat and add another radiator into the equation.

I actually mostly agree with you on this this, but for an entirely different reason.

The cooling system is designed to withstand the load of the engine, AND the Air Conditioning at the same time. To remedy an overheating engine, no, it isn't the best idea, but if it's needed to get the fans running, then go ahead and do it.. But never when set to MAX!

When your engine overheats (and by overheat in this case we mean go past 220, but not yet blow the radiator cap) what you want to do is actually crank the heater all the way up to it's maximum setting. Your Heater Core is of course a small radiator which works on the exact same principal as your large one up front. So when you crank the heat up and divert air over across it, you're still cooling a decent amount of water. Not enough to run an engine properly, no, but definitely enough to take the edge off, and in some cases avoid overheating all together and avoiding popping a radiator cap so that you're not stranded. This is especially true of older, and even late-model cars with thermocouple fans where you're going up a hill and start to run too hot and just need to make it over the crest.

Running the A/C isn't the best idea, but if it's needed to run electric cooling fans to get the engine back down to temp, that's better than nothing. EXCEPT when running it on MAX. And the reason is this right here:



This isn't just a DeLorean thing, it's an every car thing. That's the water valve that feeds the hot water supply into the Heater Core. Water is always flowing through the Heater Core, unless you've got MAX A/C turned on. At that point, aside from closing the damper door to recycle internal air only, it also closes the Hot Water Valve pictured above. So when that valve closes, and no water flows through the heater core, then you can't use the heater for additional cooling.

[mr_maxime]

Alright I'll jump it tomorrow. Running the heat probably isn't an option since the heat doesn't work in my car.

[DMCVegas]

Alright I'll jump it tomorrow. Running the heat probably isn't an option since the heat doesn't work in my car.

Is your Hot Water Valve just stuck in place? Or are you that low on coolant?

[sdg3205]

Is your Hot Water Valve just stuck in place? Or are you that low on coolant?

Or is the core bypassed?