Mgzt kv6 51 plate
 

Engine fan runs constantly even with ignition off

Fan
 

Could be the relay or it could be the temperature sensor on the blink! Its the temperature gauge working correctly or is it half way when you switch on the ignition switch?

Temperature gauge is ok not moved but not let it run too long so could be a stuck relay

Relay in control box behind bumper is stuck

Hello Dave,

Can I clear up which engine you have please? In the title of your post you say KV6 but your profile says you have a diesel. :confused:

There are circumstances where a KV6 radiator fan can run for up to a maximum of 10 minutes once the engine has been stopped with the temperature gauge remaining at the normal position.
It's very, very uncommon for a fan relay to fail on a petrol engined car.

The symptom you've described most closely matches a faulty PCB in the fan control box exclusive to the diesel.

Simon

Hi yes I did have a diesel but this is a 51 plate kv6 been in garage a long time so just recommissioned her in really good condition have give it a full service putting new brakes and tyres all round apart from number plate light and small vacuum pipe the fan seems to be only problem any help would be greatly appreciated cheers dave

Thanks for the confirmation Dave (when you get a moment perhaps you could update your profile).

You've reported that the radiator fan is running constantly with the ignition off. Does this mean that to stop the fan you've had to disconnect the car's battery?

If so, with a stone cold engine, does the fan immediately start running when you reconnect the battery with the key out of the ignition?

Simon

Hi to stop fan have to disconnect battery but does not start again until I start engine

Sorry yes fan does start with key in ignition

Thanks for the reply Dave. Maybe a typo but this is what I need to know ...
Simon

Yes I think it does sorry for being vague I only got it out yesterday and took it to work was trying to make list of everything but am sure when you connect battery fan starts

Thanks Dave.
I'm glad that you are DIY-minded because the front bumper will need to be removed to access the control box to find out what's going on. Although it remains a possibility I am reluctant to diagnose relay contacts welded together as the factory items are a heavy duty spec. made to withstand the heavy current involved.

I take it that you haven't had this ZT from new. Do you know whether the fan system is the original or a replacement and whether any modifications have been made (for example the use of a lower-rated relay)?

Simon

Would say they are all original will take bumper off during week and report back if that’s ok and thanks for your help

Please do report back, I think we're all interested to see what you find.

If original, the fan motor should have four wires and the control box lid will have KV6 printed on it.
Inside the box should be three relays. The large one should be a Siemens V23134.
Any photos you can post will be helpful.

Cheers,

Simon

Hi just checked fan does not come with ignition starts about 3 to 5 seconds after engine starts but does not go off unless you disconnect battery heater air on unit all off just wondering if something else before l take bumper off sorry about earlier information am with car all day so can have a look cheers dave

Thanks very much Dave for the correction. That's important information because it shows that relay contacts cannot be "stuck".

Don't take the bumper off yet. Can you go for a drive please with the instrument pack diagnostics activated to show the digital display of actual coolant temperature. I'd like to know the highest figure you get.

Simon

Yes will do but may late this afternoon cheers dave

Hi just done a short run in car on private industrial estate as no tax or mot yet let the car warm up with no fan on pull fuse drove it for short period no movement on temp garage at all dash reading-128
Put fuse back just same -128
I would take it to be the coolant temperature sensor in my humble and very limited knowledge cheers dave

:D Now we're getting somewhere!

If the temperature gauge is not moving off the six o'clock position, the fan is running continuously and the digital coolant temperature display (IPK diagnostics test 7.0) is reading minus 128˚C then I'd say you have reached the correct diagnosis Dave, well done! :hurray:

The coolant temperature sensor wiring leads to a connector positioned under the manifold chamber near to the purge valve. I'd advise checking that first for security since an open circuit could also cause the reading you've noted.

Simon

Thanks so much for your help will report back when all fixed cheers dave