Radiator fan motor

[Falcon_LS]

Been experiencing some cooling issues with my '01 Grand Marquis over the course of the last several months. I have a 180°F thermostat with the cooling fan programmed to turn on full blast once coolant temperature hits 206°F. Once up to operating temperature, coolant temperature is barely under 211°F. What's more worrying is ATF temperature, which shot up to 230°F in traffic. The AC isn't cooling as well as it should either.

I haven't really heard the fan on full blast for a while, and you don't feel as much air being pulled by the fan. I decided to swap the cooling fan's high relay with a spare one I had, same result. The other thing I noticed was on a cold engine, the fan's connector gets hot after a minute or two of operation. The connector is not burnt or anything, there are no codes stored in the PCM.

The Bosch fan motor is the factory original, but if the fan was the culprit, would it still work on the low speed setting?

 

[clinebarger]

Motors lose efficiency, Draw more amperage, & slow down over time/duty cycle. An amp clamp will probably tell you as much.

 

[WobblyElvis]

I would give the Radiator and A/C Condenser a good cleaning. Could make a big difference.

 

[Dave9]

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The other thing I noticed was on a cold engine, the fan's connector gets hot after a minute or two of operation. The connector is not burnt or anything,


Why would the fan be running with a cold engine? The connector should not get hot, either the contacts in it are fouled, or the wire is frayed immediately before the connector, or the motor has a shorted winding.

DC brushed motors do not lose much efficiency at all until a fault develops. It is not about time and duty cycle until one of various things happens like the insulation on the windings breaks down, or the bearings fail, or the brushes wear down, or the commutator oxidizes if it isn't ran for a long time, or the windings lose good contact with the commutator, or it gets clogged (far more likely if there's an internal cooling fan which is unlikely in exterior automotive apps).

Measuring current is a good idea, but leave the connector alone, measure elsewhere like where the relay would be. Higher than expected current signals a motor problem (assuming no wiring shorts, do check for any). Lower than expected could be a motor problem or a connector problem.

If lower than expected, then use insulation piercing multimeter probes to measure the voltage drop across the wires on both sides of the connector. I mean the voltage difference of the positive power leads on both sides of the connector, not voltage relative to chassis ground, and also, measure the voltage drop on the ground conductor wires on both sides of the connector. Measure voltage on the positive lead relative to negative too, to ensure it's near 14V when the fan should be on.

If part of these measurements are impossible because the end on the fan has no wires, and you still have not found the fault, all you can do to rule out the connector is disassemble and inspect or replace it, and/or the motor (or whole motor/blade/frame assembly, check the blades for cracks before deciding motor vs whole assembly).

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The Bosch fan motor is the factory original, but if the fan was the culprit, would it still work on the low speed setting?


In most cases a bad fan that still spins on a high setting would work on a low setting, also spinning slower than normal for that setting. A connector problem could also cause a reduction in RPM on a low setting.

Lastly, try not to get your fingers cut off.