Quick, the Manta's on fire!

Five words you never want to hear (well, if you're a Manta owner, that is)...

Jo yelled this as she got home last night and I was straight downstairs with a fire extinguisher in my hand. I got to the car, expecting flames but I didn't see anything. Initially Jo pointed to the vents and said she'd seen and smelled smoke, so I thought it must be either the A/C blower resistor or the fan that was overheating, but lifting the bonnet it looked fine. The only minor issue was the blower motor cooling hose had come off (must use a tie wrap to hold it on) and the fan was warm but nothing really out of the ordinary.

I turned the heater blower up full and sniffed the vent and couldn't smell anything so I was reasonably satisfied that all was OK.

No, says Jo, it seemed to be coming from the heater CONTROL, not the vents. Well, all seemed OK now so I told her to park it near the house as normal and I'd pull the lower part of the dash and the instrument cover off and have a look.

Off came the lower part of the dash underneath the instruments. If there was any wiring problem then it was likely to be there as that's where the bulk of the wiring terminates (that's where the fuse box is), but again everything looked OK.

The instrument cover came off fairly easily (I've done it loads of times in the 30 years I've had a Manta...) and nothing looked out of the ordinary either. One thing I did notice was that, there seemed to be a slight melted area around the lighting switch. I pulled the lighting switch out for a better look and it really did look like there was a problem. In fact, you could smell a little of the burning smell on the back of the switch, so it might be the culprit.

I reconnected the switch and noticed that as the sidelights went on the engine note changed, suggesting a large current draw. Hmmm, that should only be a few amps, certainly not enough to drop the engine speed by a large amount. Turning round to the headlamps was more surprising - the headlamps didn't come on. That was really weird, because Jo had arrived home with the headlamps on so the switch worked a few minutes ago.

I went and got a spare headlamp switch and tried it in the car, and the headlamps worked OK, so the switch had burnt out. But that wasn't the problem because I could smell the burning smell again...

At this point I finally worked out where the smell was coming from - the fusebox around the number 1 fuse was looking slightly melted! A quick finger on the fuse (and a burnt finger) and I knew I hadn't fixed the issue yet. I pulled the (hot) fuse and realized why it was hot - it was 25A rather than the 5A it should be...

The number 1 fuse on a Manta is part of the sidelamps circuit, and also powers the dash lights and the horn. This could be a big issue to diagnose as the wires for this go all over the car. At least the wires going from the fuse weren't melted (testament to over-engineering).

So first things first, let's work out what's affected by the number 1 fuse. I put the number 2 fuse back in the box and turned on the sidelights. The dash lights stayed off but the left front and rear sidelamps came on. So the number 1 fuse had to operate the right side sidelamps and the dash lights. That at least cut the culprits down to just a few possibles.

I decided to start at the back. Jo uses the right side of the boot a lot for her rucksack and gym bag, so if she'd disturbed one of the rear lamps we might have an issue back there. I looked in the boot on the right hand side and almost immediately found the culprit - the sidemarkers.

In the US you need to have sidelamps visible from the side of the car and, since the Manta didn't have them as standard, they were (badly) put on by the person who originally brought the car into the country. To wire them up they used scotchloks to connect to the main wiring harness and then just ran a pair of wires over to the sidemarker lamps. of course, in an unlined boot like the Manta's, those wires can easily be pulled from the sidemarker lamp unit and just end up dangling in the boot.

In a fit of uncharacteristic tidiness, Jo had obviously pushed them behind a piece of insulation and that had been fine, right up to the point where the live wire touched a rusty spot. The rust had conducted just enough electricity to avoid the fuse blowing, allowing the circuit to overload and overheat with the large current it was drawing. The 25A fuse had meant the circuit didn't blow as it should have done.

Jo had stopped at the drug store on the way home and had luckily only had the headlamps (and therefore sidelights) on for a mile or so, otherwise it may have been a lot worse than it was...

So everything's OK now. I checked each fuse and put in the correct one (most were wrong) and I've also reconnected the sidemarker lamp wires. I must make a better solution for the wiring for the sidemarkers when I have time, but at least Jo knows what can happen if the wires hit bare metal!