A different CDTi fan problem

RayH · 16th July 2015, 13:42

In a nutshell 2 speed fan with neither speed working, fan runs if you apply 12v directly.

A bit of background, I bought the car recently and noticed no low speed fan, didn't try high speed at that point.

A couple of weeks ago I took of the silver resistor, found it to be open circuit and replaced it. Re-assembled, still not working, bridged trinary switch - nothing!

As the car isn't my daily I got around to having another look today.
Stripped it out and found if you apply 12v to fan it runs, so no motor issues.

I have 12v on the connector in the wing, so fuse okay and ground on the other connector. I have checked the relays in the fan control box, by removing them and testing with 12v to coil and continuity across switched contacts.

So what am I missing?
Am I right in thinking the trinary switch when bridged by-passes every other control, so I'm not looking at ECU or anything horrible?
The only thing left that I can think of is the PCB in the fan control box itself.

Your thoughts would be appreciated gents - thanks Ray

16th July 2015, 13:42	#1
RayH Posted a thing or two Rover 75 Saloon Join Date: Jun 2009 Location: Kidwelly Posts: 1,649 Thanks: 287 Thanked 276 Times in 238 Posts	A different CDTi fan problem In a nutshell 2 speed fan with neither speed working, fan runs if you apply 12v directly. A bit of background, I bought the car recently and noticed no low speed fan, didn't try high speed at that point. A couple of weeks ago I took of the silver resistor, found it to be open circuit and replaced it. Re-assembled, still not working, bridged trinary switch - nothing! As the car isn't my daily I got around to having another look today. Stripped it out and found if you apply 12v to fan it runs, so no motor issues. I have 12v on the connector in the wing, so fuse okay and ground on the other connector. I have checked the relays in the fan control box, by removing them and testing with 12v to coil and continuity across switched contacts. So what am I missing? Am I right in thinking the trinary switch when bridged by-passes every other control, so I'm not looking at ECU or anything horrible? The only thing left that I can think of is the PCB in the fan control box itself. Your thoughts would be appreciated gents - thanks Ray