Electrical Ignition gremlin...any help much appreciated

[bonnietiler750]

Just got back from Manchester Airport collecting my Missus, at the lights (huge M56/Bipass junction...of course!) and everything cuts out without warning (this is a Mk2 Auto) I still have lights and Starter motor but no ignition or warning lights indicator lights etc, all interior lights still work, Push car across junction then warning lights are back on, car starts, but only runs for 1/2 mile before fault repeats itself. Wait it starts again etc etc. Get home all fuses are intact of course...could this be the inhibitor switch? why would it be so intermittent,is it heat related. Its my Daily driver so if anybody has an idea please advise!
Many thanks
brian

[trunt]

Ignition switch?? Or plug from it??

Looking at the circuit it has 4 outputs. one is for the starter, one for the radio, one for the Lights(Red wires) and one for the rest (white wires) If the white wire output was bad it would give those symptoms.

On my federal Mk2 cct diagram the battery voltage guage is connected to the white wire.. that may give you a clue..

Its not the inhibitor switch, that would only stop the starter from working

Terry

[bonnietiler750]

Thanks very much, I'll have a look see

[Phil S]

the white wire on the back of the switch had a dry joint on mine, similar problem, looked ok bet fell out with a little wiggle

[DZP]

Hi,
I would be suspecting the ignition switch or the wires from it to fuse panel position 19.
As the starter motor is working, even in fault condition, you must have power to the ignition switch.
On MK II, the Ignition switch output feeds to position 19 on the fuse panel, but it cannot be anything associated with the fuses as you have also lost ignition and instruments, which also feed direct from fuse panel position 19.
As the fault seems to disappear after a "cooling down" period, I would be particularly suspicious of overheating of the connections between the ignition switch and fuse panel position 19 and look for melted wires or loose connections.
If you cannot see anything obvious, then if you have a voltmeter (or spare bulb holder), I would debug as follows:-
Remove the steering column cowl, exposing the ignition switch.
During fault condition, with ignition switch on:-

• Check for 12v at the Ignition Switch white wire.
• If OK, check for 12v at fuse panel position 19 (top of wiper motor fuse)
• If no 12v, then check for 12v at white wire on the steering column Ignition Switch connector plug

I hope that helps.

[PJM Stag]

Not sure if this applies to your car but do you have the insulated connection in the drivers footwell?

[bonnietiler750]

I'm not certain I've never looked

[trunt]

I think he means the terminal on mk1 cars that feeds the battery power into the cabin.

It would only be there if you had a very early mk2

terry

[bonnietiler750]

I had a spare ignition switch and I have fitted that made no difference,I did notice that the voltage meter was showing zero just prior to the last failure,I even swapped the alternator to zero effect..its almost like the car has an immobiliser

[jbuckl]

If / when it fails again, try bridging fuse 1&2 together.

[bonnietiler750]

I have just bridged Battery Control (Fuse 1/2) to Ignition Control (3/4) everything works when this is done, I'm assuming that I am bypassing the Ignition switch by doing this?

[bonnietiler750]

Just a thought when I am bridging the two fuses I can clearly hear a relay, could this have failed on the ignition powering connection?

[trunt]

Just a thought when I am bridging the two fuses I can clearly hear a relay, could this have failed on the ignition powering connection?

Probably not, you are supplying the voltage to the circuit by bridging (when the ignition switch is failing to do that) and it energises, as it should.

You are going to have to chase the circuit. I would start at the plug under the steering wheel, its the one with 2 thick brown wires, white wires (2into1) a white/pink and a red and a white/red starter (at least on mine!) find the white wire pin (mine has 2 together on one pin) unplug it and check between that pin and the fuse 3-4. then if you want, between that pin and a white wire in the instrument panel, the voltage gauge is a good place.

From your description I would say they will be OK the gauge feed and the fuse are seperate wires so unless you have both wires burned up -- unlikely especially as feeding the fuse gets voltage to the instruments via that pin!

Then you can check the ignition switch, on the steering column side of the plug. check between one of the brown wires and the white wire, with ignition on it should be a short you will need to try both as one brown is for lights, the other for ignition, by your description both of those seem to have 12v as 1.you have lights and 2.a starter.

That should isolate where the problem is.

Hope that helps