I've just come to the forum with this problem on my 2005 Octavia. The resistor pack was replaced by me on purchase in November 2008 because it only worked on position 4 and lasted 8000miles until August 09 when it was replaced again due to the same fault. I shrugged it off as a poor quality component due to the volume of complaints on this forum but it has lasted not 3 months and 3000miles and gone again. I am buying a third resistor pack inside of 12months! I am tempted to replace the fan motor at the same time as I cannot see what else can be causing this component to overheat. Can anyone advise what can be causing repeated failure other than a dodgy fan motor?

Have you access to a test meter so that you can check voltages and currents ?

If the resistor pack overheated, it could have melted some wires somewhere and this will be causing a short. For it to burn out a second time suggests that there's too much current going through it, again indicative of a short. Without a test meter and some readings, we'd just be guessing where the problem lies.

D

Try removing the fan and cleaning the turns of the coil and lubricating the bearings.

The whole assembly is open to dirt and moisture, so the coils become clogged with dirt and grime where the bushes/bearings become a little stiff.

I'm only assuming it has failed due to overheating...is there some sort of thermal protection built in so that wires don't melt and you lose all the positions 1-3 rather than one at a time? There is no discolouration or external damage to the pack (due to ceramic coating?) I'm assuming (again) that a fault in the fan motor or the high resistance due to dirt or blockage you speak of is causing too much current to flow through the resistor pack. I can lay hands on a multimeter and I suppose I'll need a new resistor pack to make any checks?

If there's a transistor in it, the transistor normally burns out to protect the fuse

40A is excessive - that's 480W (or 0.7BHP in real money). If you're blowing 40A fuses, then most test meters will struggle to measure that sort of current. You'll need to measure the current flow indirectly, possibly by fitting a known low value high power resistor in series with the motor (0.1Ohm, 200W) should give a drop of 1V per 10 AMPS (or 0.01 Ohm at 25W for 0.1V/10 Amps).

TBH it sounds as if the motor is really knackered. It's probably overheated due to the bearings drying out and the coil insulation has melted shorting some of the windings either to earth or to each other.

Regards,

D

You' ve helped me make up my mind - I'll throw £76 for the motor plus another £28 for resistor pack - and fingers crossed after that - at 96k you've got to expect these things! I'll comment again if the new and old fan motors feel very different when they are out. I appreciate I can possibly lubricate / clean up the bearings but the fan is quiet and runs smoothly when the pack is working. The electrical checks you kindly suggest are beyond my knowledge/skill sadly.

A can of carb cleaner some good quality oil and a hour of your time would be alot cheaper in my eyes matey.

Removing the fan is a case of unplugging the loom, then twisting the housing and pulling it out.

Press out the 3 rubber bungs holding the motor to the plastic assembly. Watch the wires though as you do as it will still be connected to the housing. Flush the windings with the carb cleaner and allow to dry, then apply a good quality oil to the bearings the shaft and give it a few turns then repeat it a few times in as they will more than likely be rusty. Rebuild the motor and re assemble, then fit a new thermal resistor pack.

Or the resistor packs can be repaired with a new thermal resistor, the problem being if the poles become too hot the resistor can slide down and short the pack out blowing the thermal resistor again.

But then again i wish i'd have thought about that in the first place, as i'd have found another way to secure it so it didnt drop in the event that the solder did melt down to a high resistance.