Cooling fans won't turn off

[kenny]

Hey all,
A strange issue.
When I turned the car off last night the cooling fans kept running for a few mins. The only way I could get them to stop is with the battery disconnect switch. Repeated process: Started the car again, no fans on. Turned on the aircon again and fans came on, switched off engine again and the fans stayed on and wouldn't turn off.

I have Dave McKeens new fan relay and his fan fail relay and both have been working great for a few years.
The fan relay keeps the fans running for 20 secs after engine is turned off.

Looking at the electric schematic the otterstat should not affect the fan relay when key is removed.
Likewise the compressor wire to the relay is only on when the accessory relay is on.

Hopefully will get a chance to look at the car today. Will be easy to check with a multimeter, initial thoughts are that the fan relay is failing closed but am I missing something else obvious?

[Bitsyncmaster]

Check your ground pins (resistance) back to the common ground point (I use the group of black wires at the back of the relay compartment.

Also check the fan relay if it shows any heat damage.

[David T]

Check your ground pins (resistance) back to the common ground point (I use the group of black wires at the back of the relay compartment.

Also check the fan relay if it shows any heat damage.

The next time it happens pull the fan relay. If the fans stop the relay is stuck.
David Teitelbaum

[jjdaily]

I have also had the otterstat fail in the on position.

[kenny]

Thanks for the feedback guys.
Did some testing.
Relay shows no sign of heat damage.
Unplugged all the cables from the relay socket.
The ground wire is good, less than 2ohms resistance to main ground.
The black/ orange wire from the otter stat/ ac compressor drops to 0v when mode switch is turned off and 12v when on so it functions ok.
Live feed gives over 14 volts with engine running.
When relay is plugged in the fans will not shut off after ac is turned off and there is also a 9 volt reading at the black/ orange wire when fans running. Looks to be an internal problem with the relay so it is giving voltage out this pin.
When I physically unplug this wire the fans sometimes stop 20 secs later, sometimes not.
I will bench test with a 12v power supply on Monday but am 99% sure the relay is at fault.