Yet more fan woes.

[BillyBoy]

Following on from this thread:

http://forums.mercedesclub.org.uk/showthread.php?t=49841

I had a new fan fitted (non-MB), which went ok for a couple of months, then it failed - The fan was coming on full speed whenever I started the engine. The diagnosis from Malcolm, myself and a garage all concured and pointed to the fan control unit. Took the fan back to KMS where I got it from under warrenty and exchanged it for another. Fitted this back in September and it was fine until Tuesday when the same fault occured. Fan now doesn't run, but I do get an error on the dashboard telling me the fan has a fault (interestingly this didn't happen with the other the fans when they failed).

Question is, is there any underlying issues anyone knows of that can cause this? The first fan was the original as far as I know and it is conceivable that this did fail after 5 years and it failed by not operating rather than running full power, however for the other two failing so soon after fitting, though possible, seems unlikely.

It could be coincidence and possibly a bad batch from the manufacturer, but before fitting yet another fan, I want to try and rule out an underlying problem with the car.

Cheers,
Bill

 

[television]

Only water from a blocked air intake could cause damage. you can try the fan on 12v from a battery charger or the cars battery, if the fan is running only at its slowest speed then the regulator could be at fault and a common fault.

Nothing other than water could cause it to fail

 

[BillyBoy]

Which air intake do you mean Malcolm? This is the engine cooling fan, so the only air intake is via the radiator. Couldn't see any intake into the control module, that seems to just have a vane heatsink on it to disapate any heat from the (presumably) power transistors that control the fan speed, but apart from that are sealed units.

I don't think I can put 12 volts across the motor as it is a multipole brushless motor, and needs the control from the unit to turn I think. It has permenent power supply (when ignition on) and two data cables which presumably send the required speed from the engine management unit.

Do you know if the data circuits are 12 volt on these or are they 5 volt? If they are 5 volt, I can imagine that a fault on the data bus could blow some control circuitry, but I would have thought they'd have a zener or something to protect against that, and would have thought it unlikely to be isolated just to one component.

As I say, it could be coincidence as I can't really think of anything that could cause the fans to fail, but it does seem odd. (having said that, I do tend to be naturally unlucky ;-)

Cheers,
Bill

 

[television]

Sorry I did not read it properly,and I was refering to car heater fan.

The fans are 12v, but the ECUs could be any voltage, and I will take another look, there are such things as bad batches