Help....I turn off the ignition and then my problems start

[Tim-b-123]

Hi,

This is one of those questions that either no one has ever heard of before and you'll burst out laughing, or if I search though this forum it's a known problem !.

On turning off the ignition, the engine stops (as you would expect) but the two cooling fans immediately come on (whether the engine is hot or not). They do not time-out and if left will continue forever. Starting the engine removes the problem.
If I turn the ignition back on (without starting the engine) and a couple of minutes have passed for the immobiliser to kick in, the fans stop BUT all the ignition lights turn on and remain on even when I remove the key.

So, whenever I park up the only option to avoid a flat battery or leaving it with the ignition lights on, is to go into the footwell and disconnect the battery !.

My first thoughts are a stuck relay, but this is a guess and I'm not sure which relay to check.

Any help would be appreciated.

Thanks
T

[pupp]

Are you sure the fans are not running when the engine is running too (you might not hear them)? The circuitry for the fans is pretty simple and the switching is done by an 'otter' switch that senses coolant temperature... these are notorious for playing up and are not an expensive part. If someone has wired the fans to a permanent live rather than through the ignition (ie to give some fan over-run when leaving a hot car), then a faulty otter may well cause what you describe. As an easier work-round in the interim, you could just pull the wires off the otter, which is on the bottom of the swirl-pot. Commonly this is also the point where a manual switch is wired in to let the driver turn on fans at will.

[Tim-b-123]

Hi Pupp - thanks for the response, but I've already investigated that and the fans work as they should when the engine is running. The problem starts when I turn off.

[Cider Andy]

The symptoms you've described don't make sense. When electrical things don't make sense, suspect a faulty earth.

[pupp]

Maybe not much immediate help but something to be aware of is that some cars get modified by the addition of a 'two stage' fan kit that either alters fan speeds or independently switches the two fans at specific temperature points. I've not had any experience of these but there will be some 'logic' at work (probaby using relays etc) that is more complex than the standard simple arrangement. I suppose IF such a kit was fitted and somewiring defect like a bad earth occurred then strange behaviour could arise. Start by pulling fuses and checking earths... afraid it's one of those that needs a patient and methodical approach. Just trying to remember if anything eles shares the fan fuses... someone will be along who'll know. Good luck.

[TVR keith]

I think the horn is on the same circuit, not sure how that helps, perhaps disconnect the horn and see what happens then

[pblake]

Is the charge/battery light working as it should with the ignition on. if not you could have a diode gone in the alternator back feeding the ignition with it off. Other than that bad earth would be favorite.

[jonathant]

I've the exact same symptoms but still not diagnosed the problem yet. Apparently there's an earth strap around the front of the radiator that gets easily corroded. When I get the chance this is the next place for me to look.

[shpub]

It;s actually under the radiator...

[tim-b-123]

Well I've cracked it (or the garage has !!)

Despite checking every earth I could find, the otter switch, checking various circuits as advised by you all (thanks for your suggestions) - nothing.
I still had the same problem, the cooling fans and the ignition lights coming on when I stopped the engine.

So for your information and to stop you having to spend a fortune on garage labour charges, if the problem either appears on your car or you read about it here .......check the relays.

Apparently there was a fault on the fuel pump (or fuel ignition) relay - both situated near the main fuse box. Once the engine was switched off there was an electrical leakage back towards the ignition and cooling fan circuit.
Replacing both the relays (to be on the safe side) sorted the problem out.

As I said earlier, thanks for the advice.

Tim

[pupp]

Those relays are certainly known for causing occasional problems but that's the first time I've seen those symptoms described as a result... strange one! Glad you got it sorted, these sorts of things can be a nightmare and cheers for sharing the outcome. One to remember.