bizarre cooling fan operation

[jonathant]

ok, I'll start by saying that apart from a leaky radiator (which is going to be fixed soon) the cooling system on my 99 Chim 450 behaves as you'd expect it to: comes up to temperature quickly-ish; fans come on for a bit; fans then go off; fans do not run when car is turned off; etc etc.

so, the following happens maybe once a month and only when starting from cold: I go to the garage, start the car and back it out then realise I've forgotten something so turn off the engine. Hmmm, cooling fans come ON. Turn on ignition (but don't start car), fans go OFF. Turn off ignition, fans stay off. Restart car - everything back to normal.

Thoughts?

[shpub]

Bad earth or poor connection on the fan connectors.

[jonathant]

for my benefit, how would this make the fans go ON when the ignition is OFF?

[shpub]

What happens is the the electrical current can find different pathways and all sorts of funnies can occur. Like wipers coming on unexpectedly when the indicators are used. The main earth for the fans is bolted under the rad. If that is leaking, quite common for it to corrode and become a bad contact.

[dlewis]

sticking relay???

[alanw]

what can you do to fix a sticky relay? Is the solution just to replace??

[minirace]

Had the same problem with my 430 chim for years, I replaced the earth lead to an alternative good earth. both the fans now work perfectly all the time and it never gets too hot. Been ok for about 2 years now.

[red griff roger]

Don't forget anything when you leave the garage

[M@H]

red griff roger said:

Don't forget anything when you leave the garage

[jonathant]

well, as a follow-up, my local diagnosed the problem to a faulty "trinary switch" - something to do with aircon. Now replaced - fingers crossed.