Cooling fans constantly run

Question

This past summer, I inherited a '95 Pontiac Grand Am that, while looking under the hood, I noticed someone had removed the air conditioning unit. I drove it throughout the summer and it wasn't until the winter that I noticed that it was taking a great deal of time for the car to warm up (something you notice quite quickly in northern Wisconsin). It was then I realized the engine cooling fans where constantly running. Just to make sure there was nothing else up, I double checked the radiator and engine coolant hoses and found no leaks and the levels were all normal.

My question is, besides just running cooler, are there any other things that I need to be concerned about with the fans running constantly?

Answer 1

You may have two problems.

Even with the cooling fans running all of the time, the engine thermostat should force the engine to warm up at a normal speed. The thermostat will regulate the coolant to the radiator/fans if it is working properly.

It can be normal for the cooling fans to run constantly under certain conditions. If the car is hot enough, they may be barely keeping up with demand and stay on. Also, most cars will run the fans at a high speed if the A/C is turned on. However, when you first start up a stone cold car with the A/C off, they should not be running.

If they are, the ECU is commanding them on falsely (bad temp sensor or it thinks the missing A/C compressor is "on") or the relay may be stuck closed. Usually you can find another relay of the same type in your fuse box and switch them to see what happens. Testing at the relay would also reveal if the ECU is constantly requesting the relay to the on position.

Answer 2

On some cars, the cooling fans have their own thermostats or are triggered by coolant temp readings on your ECU.

While you don't want your motor to overheat, you want it reaching operating temperature quickly as this is where your motor is most efficient - e.g. lower emissions, better mileage.

Answer 3

Can you describe the behavior - are both fans running constantly, or is one cycling w/ the other constantly on?

Most modern cars with electric fans usually have 2 - one for regular cooling (typically switched by the ECU) and an auxiliary fan for AC. Aux fan control is generally run by a relay, usually tied to whatever engages the compressor clutch (typically the AC switch on your dashboard).

I would be willing to bet when the compressor was removed, someone jumpered out the cooling fan relay(s) so both fans run constantly.

Answer 4

Yes, your fans running constantly indicate a problem. From what I've found in my search, the fans are supposed to come on when your a/c is on, which considering you don't have one anymore might be what started all this. Perhaps the "turn fans on" control from the a/c is active low? With it gone, the fans would then run all the time. But the fan control might come from the ECM. I'd have to look at the wiring diagram for the car. Do you have a shop manual for it?

The fans running constantly would obviously slow down your car's ability to heat up the cabin. The only other worry would be related to my comment above. If you are sure that the actual engine temp is normal, there's no problem. I can think of a scenario where it would be bad such as if the coolant pump impeller is worn. The fans would be trying to make up for it and the cabin temp would be slow to rise because the coolant wouldn't be circulating through the heater core properly. But if that were the case, the temp gauge on your dash would show the overheating issue so I doubt it.

You might wire up a switch in series with the fans to keep them off. But keep an eye on your temp gage to be sure everything's Kosher without them. That's sort of a Sanford and Son approach.