Fans on randomly - engine off and not started for 2 weeks

[FlipFlopGriff]

Mrs FFG walks by the Griff and the fans are running at full speed. Car is on the drive and not been started recently so why are they on? Given shes just had a knee op and struggles walking disconnecting the battery wasn't an option so got her to disconnect the connections at the top of the rad which did stop them. Anyone know where I can start to look to see where the problem is?
FFG

[BJWoods]

Otter switch playing up...? just this week mine had fans coming on, when started from cold.. and staying on all the time.
after a week of doing this, it has cured itself!.. could just be a bad connection?

[FlipFlopGriff]

Thanks Barry. Strangely was happening on the pre cat earlier in the year and changed the otter. Is OK now but haven't driven it since. What are the chances of 2 going (this time the 500) at the same time?
Where does the wiring go when it disappears behind the rad, ie any more connections other than the 2 I can easily see/get to?
FFG

[pb450]

I thought the fans were on the ignition circuit. Clearly not if they were running without the ignition on. Very odd...

[ruaricoles]

Yes they should be on the ignition circuit surely

Paul did your fans previously run on when you switch the engine off when it’s hot?

Ruari

[Aussie John]

Hi Paul, you may find if you had disconnected the otter switch the fans will still run and the problem is the relay contacts are stuck on. the otter switch circuit is switched via the ignition but the relay contacts are not. Good luck, cheers, John.

Edited by Aussie John on Friday 10th November 06:48

[anonymous-user]

Remove wires from otter switch, link them and if the fans run the 12V is ok. Not sure you should have power without ignition on tbh. On mine the insulation had been melted away shorting it all out.

[FlipFlopGriff]

Ignition wasn't on, in fact the car was locked. It was only when a neighbour walked passed the Griff did she notice a loud noise.
From memory the fans don't run when the key is out?
FFG

[anonymous-user]

Has to be a short somewhere to 12V. I would get in and around the wiring and move it around with the ignition off and see if you can duplicate the issue?

[Monkeylegend]

Have you got an override switch that has been knocked on somehow, but bypassing the ignition switch?

[Penelope Stoppedit]

Hello FlipFlop
You may find it worth your while in first proving that the fans are wired through ignition +ive or permanent battery +ive

If wired to permanent battery +ive, the fans could operate when they shouldn't be due to a faulty otter switch, a faulty relay or a short in the wiring harness

If wired to ignition +ive, the fans could operate when they shouldn't be due to a faulty relay or a short in the wiring harness. This is if the otter switch is switching a ignition +ive and not a earth/return

Something for you to think about is "perhaps the relay has moisture/water in it"

[anonymous-user]

My fan wiring to the otter switch. The wires had been twisted together and the heat had got to them. The insulation was missing all the way back to where the loom came out of the block area.



It was switched via the ignition but if it had been a permanent live it would have shown a similar issue to the OP.

[Steve_D]

Penelope Stoppedit said:

Hello FlipFlop
You may find it worth your while in first proving that the fans are wired through ignition +ive or permanent battery +ive

If wired to permanent battery +ive, the fans could operate when they shouldn't be due to a faulty otter switch, a faulty relay or a short in the wiring harness

If wired to ignition +ive, the fans could operate when they shouldn't be due to a faulty relay or a short in the wiring harness. This is if the otter switch is switching a ignition +ive and not a earth/return

Something for you to think about is "perhaps the relay has moisture/water in it"

Faulty relay has to be a strong possibility as the power contacts in the relay are permanent +12v and the actuating coil is ignition switched +12v.
So water or burnt/fused contacts could be passing permanent +12v to the fans.

Steve

[FlipFlopGriff]

Connected it back up after a few days and its been fine since.
FFG

[Penelope Stoppedit]

Possibly dried out over time

[tofts]

If in standard trim, Fans on after car off is a sign that the relay is sticky. Given a tap, it will probably stop.

I see it a lot with cheap Chinese relays.

[mhag]

Same problem, wife reporting strange noise from garage, I was at work & had to talk her through disconnecting the fan
Same problem when I left the car at TVRSSW, Col was just closing shop when he heard the fan come on on it’s own...
Faulty relay...
All good now

[jesfirth]

I had exactly the same last year - mine was brittle wiring above the rad allowing the wires to short out.. the biggest problem was that I use a special very light 2kg li-ion battery which the fans flattened so it killed the battery - that cost me £400 for a new one!