Crossflow - thoughts please for an electrical mystery...

[simon metcalfe]

My car (1990 Crossflow) has mysteriously developed an electrical fault with the instruments and some components which I can't diagnose so I have arranged for an electrical engineer to check it.

I suspect it's an earthing issue but I've checked them all - battery, front to chassis and under the dashboard near the wiper motor - all look fine, as do all the wires and connections.

 

The car was running perfectly last October when I laid it up for the winter. All I’ve done is replace the distributor and coil (with parts supplied from Mick & John when they were still at Redline), and refit the battery which I remove for the winter. I have also disconnected / removed the old Lucas ignition amplifier – and I’m wondering if in doing this (feeding the plug through the bulkhead) I may have dislodged an earth wire or something from the ignition switch – although I can’t see or find any loose wires. I have checked all the fuses - all ok.

 

Symptoms.

 

If the ignition is off – when I switch the sidelights on the blue (main beam) light comes on on the dashboard and the temperature gauge needle goes to max.

 

If the ignition is on (not engine running, I don’t dare try to start it in case it causes further woes, although I'm advised that the ignition circuit is separate from the rest of the wiring) – the red ignition light comes on sometimes but usually not. The fuel gauge reads as normal – but when I turn on the side lights, the fuel gauge switches off (I think its like the polarity has been switched on it) and the temperature gauge goes to max. The indicators don’t work either (tried a new switch) but the hazards are fine.

 

All the lights are working ok, including the brake lights. The wipers don’t work, the washers are ok, and the air horn doesn’t work – the pump weakly whirrs but I think it may be going backwards!

 

The battery voltage is 12.36v ign off, and 12.32 ign on. I’ve checked the voltage to the earth too and that is also 12.3v so I don’t think it’s a main earth issue.

 

I connected all the ignition wires correctly, but have also disconnected it all just in case this was the cause somehow – but it makes no difference. I have also double checked all the connections on the alternator and starter which are fine.

 

Any assistance or suggestions which may help the electrician  would be hugely appreciated as I can’t think of anything else I can check.

 

Kind regards Simon Metcalfe.

 

[revilla]

You couldn't possibly have reversed the battery connections couldn't you?

[Piers300]

Sounds a tricky one Simon. I am sure someone will be along soon to point you in the right direction. 

Hope all well otherwise.

regards

Piers

[elie boone]

did you check the earth connection to the engine ?

[Wrightpayne]

Water ingress to the fuse box?

[virden]

If all the battery connections are correct, take a look under the scuttle, my  X/F (96)  came with a load of loose/ seemingly spare wires there and I found it was easy ( but not obvious) to have disturbed these and cause a localised short when pulling cable through the grommets in the bulkhead.
 

[randybugger]

Double check the wiring you changed, could you have put a live wire to earth that only gets power once the ignition is switched on?

 

[Ian Mackenzie]

Sounds like an earthing issue somewhere....

I'd double check all the wiring that you've touched as discussed, it may also be worth checking the voltage regulator for your instruments you have one fitted, given some of the issues with your gauges...

Cheers

Ian

[john g]

Clutching at straws.......how about putting the old coil and amplifier back and see what happens. ie eliminate what may be a faulty new component.

[Jonathan Kay]

Fascinating problem, and I still can't explain it with one razorish or a few specific causes. Hadn't thought of #2.

My general approach would be to isolate one or more circuits from each other until something worked as it should, then build back up again one at a time until something went wrong. 

Hope you're back in business tomorrow night, and looking forward to the answer.

Jonathan

[Ivaan]

Start by pulling all the fuses & relays one at a time. See what differences, if any, each makes.

[simon metcalfe]

Hello everyone. 

Just thought I'd report back with the now resolved electrical issues.

There were 3 x simultaneous issues...

As suspected (and seems nearly always the case) the main culprit was a poor earth - it was the one under the dash near the wiper motor. Interestingly I'd checked this and all "seemed" ok - but the auto electrician could tell it was poor from his multimeter - tightening the nut with a ratchet sorted this.

Secondly - the hazard light switch (again very temperamental as rarely used) was causing the indicators to fail. This was resolved by soaking it in switch cleaner and turning on and off a few times.

Finally, the ignition light (sometimes on sometimes not with the key at position 2 in the ignition) - this is caused by a poor connection at the alternator - it's the smaller of the 3 x wires. He tightened the connector which seems to have fixed it for now. He pointed out that it's important that this is working correctly otherwise the battery won't charge!

I'm pleased that the new ignition arrangements had nothing to do with the above.

So, thanks to you all for your help - and especially to Jonathan for sending me the wiring diagram which was very useful indeed.

Cheers Simon. 

[john g]

Thanks for the update and pleased it's sorted