Radiator fans - advice please?

[steve_earwig]

Knowledge base, knowledge base,
riding through the glen...

[Owenmc]

I know know as far as cars with the Bitron fan ECU go, but on them, the fan ECU gets its temperature from the engine ECU which gets it from the coolant temperature sensor which'll probably be located near the engine-end of the top radiator hose. Unplugging the sensor connector should cause the fans to come on at full speed as the car will think it's hotter than the sun...

Having fan trouble myself, and a quick skim of the existing threads led me to this one, which seems to fit the bill, so here's to reviving a bit of an old thread....


OK, well for some reason my sensor seems to be acting as if it's disconnected - fan is on 100% of the time, pulling merrily away even when parked with the keys out.
- Engine temp is normal when running - below normal actually, with that much cold air being dragged through the rad.
- Checked round the fuses - nothing blown
- unplugged the sensor and checked connections visually - no reason for contact not to be made, and it was seated properly to start with
- have so far not located the other end of that line - warps itself up into the loom is all I can see - I'll need more light to dig into it further - I'm not exactly the best with cct diagrams, and torch-light is useless to me... just a bit too colour-blind
- yanked the relevant fuse from the engine-bay fusebox to shut it up overnight (no sign of it wanting to shut down at all), but that's no real fix....

Car's a D9, 2l petrol, 2001/Y, aircon, 66K on the clock

Q: How fragile/prone to failure are these sensors ?
Q: Or is it more likely to be the other end of that wiring, wherever it leads?
Q: Any 'try this fix' ideas, before replacement (which'd be a garage/mechanic job - spannering is not my forte :-/ )

thanks,
Owen

[mjb]

First thing I'd suggest would be to test and/or replace the fan relay (sorry, can't tell you which one that is). Then I'd try looking at the coolant temperature sensor. If you can find out what resistance (ohms) should be across it for a given temperature, you can test it with a multimeter, otherwise replacement will cost about £10 I think from a dealer, plus fitting which should take an independent garage about 15 mins

[Owenmc]

First thing I'd suggest would be to test and/or replace the fan relay (sorry, can't tell you which one that is). Then I'd try looking at the coolant temperature sensor. If you can find out what resistance (ohms) should be across it for a given temperature, you can test it with a multimeter, otherwise replacement will cost about £10 I think from a dealer, plus fitting which should take an independent garage about 15 mins

Thanks MJB -

some good news - it's 'gone away'.... That's good news, isn't it

All relays clean as a whistle - all looked as good as new, to be honest, and after I put all that back together again the
fan was still blowing a gale with or without ignition switched on.

Not feeling confident with the temp sensor removal & check I booked a check with a local guy, but when the fuse went
back in this morning (stop/start Monday, seemed wise), all was fine...... I'll be keeping an eye on that, all the same.

[r8tdi]

hi i was wondering if you managed to sort this problem as i have the same problem but i just cannot seem to get the cowling or fans of any advice please?

[mjb]

If there's not a HOWTO in the knowledge base section of the forum, I'll make one in the next couple of weeks when I attempt the job if you can wait a bit