So the CJ passed its test, BUT... (there's always a 'but', isn't there?)

[strangeangel]

Aced it. No advisories or anything...

 

BUT after it had been sat running for a while for the emissions the tester backed it out of the garage and turned it off. The fan was on by now and kept running once the engine was off - nothing unusual to start with - except that it stayed on. I had to go to work, about five miles away, and it was still on when I got there. There were no warning lights and no signs of overheating so I just disconnected the battery while I was in work, thinking I could sort it when I got home.

 

When it came time to leave, two hours later, I connected the battery. No fan, so I drove home. Parked up on the drive and set about doing a couple of jobs in the garage, when after about five minutes the fan came on again. I opened the bonnet and there was a burning smell now, and small wisps of acrid smoke. I opened the little fusebox by the radiator and pulled a 25A fuse which killed the fan. I have disconnected the battery again, just to be sure we don't have any embarrassing fire-related cock-ups while I'm here typing this.

 

Any ideas what's causing this please?

 

[DaveAspley]

Unplug the fan and unplug the switch. Connect a voltmeter to battery negative terminal and probe the pins on the fan plug to see if it's picking up 12v from somewhere, ie a short from another circuit. If no voltage is present then most probable cause is the fan switch.

[strangeangel]

Thanks Dave, I only got as far as unplugging the switch. That's what had melted and it broke off, leaving half of it stuck in the wiring connector:

 

 

I'm thinking this was caused by the damaged wiring here:

 

 

which in turn was caused by coming into contact with this (presumably very hot) resistor, which was just dangling down amongst the wiring, rather than being fastened up out of the way somewhere:

 

 

I've ordered a new thermo switch, but I also need to replace the knackered bit of wiring loom that connects to it...

[strangeangel]

Update: The charred bit of wiring will soon be replaced courtesy of E. CABBAGE ESQ. of this fine parish