Corsa - burning out fan speed resistor assy.

Oct 12, 2009 4 Replies
D

Control of the ventilation fan in SWMBO's Corsa is achieved by large green cement resistor with taps at speeds 1, 2, and 3 (speed 4 is flat out, no resistance or current limiting in circuit).



The body of the resistor is mounted on a metal bracket and the



+12volts is fed to the resistor through a thermal cutout mounted above (?) the resistor, spot welded to the iron (?) terminals.

It would appear the current limiter largely exists to monitor the cooling effect of the airflow through the fan, or then again maybe it doesn't.



The whole assembly has a scandalous price and on SWMBO's vehicle the thermal cutoput keeps on blowing. I have bought replacement thermal cutouts but mounting them is a problem because the originals are spot welded.



I was wondering if the cutout is there to monitor the temp. of the whole assy. It is not in circuit at the fastest speed and the performance of the fan then is entirely normal.



Has anybody any better idea what this sorry mess is intended to achieve?



Right now I'm more or less set to bodge it without the current limiter



Derek



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D

Well it stops your fan resistor catching fire.

That's the idea, at the fastest speed then the resostor pack doesn't generate any heat.

That'll just let you burn the resistors out. If it's overheating then there isn't enough airflow, either the fans dirty or sticking ( or the thermal cutout's died but if the replacement ones are going then that's not the issue). You can glue the cutout down with heatsink glue or tape.

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M

does it have the blocked pollen filter that often causes this fault?

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R

The heater resistor pack went on my astravan - started to loose lower speeds then only fast would work. Fitted a 2nd hand but could only get one from a corsa. The connections were the same but it was a different shape and wouldn't fit in the hole under the pollen filter. I re-located it to the opposite end where it now gets a good cooling blast from the fan. Months later it's still working ok. At the time I read on one the Vauxhall forums that the thermal fuse often blows way before it reaches anywhere near critical temp and to fit a slightly higher temp range fuse (about 70p from maplins).

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D

Sorry I dunno the ins and outs of circuits of electrickery. However:

Check for restrictions in the airflow. As others have mentioned a blocked pollen filter or buildup of leaves/dead spiders could be the cause.

I'm not sure what the ventilation arrangements are for a Corsa, but on a

306 in my charge, the cable that controls the airflow flap into the cabin became detatched, the flap jammed shut and the lack of cooling air blew the resistor pack.

New resistor pack was £10 from the dealer.

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