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MG MGA - Very Odd Electrical Glitch

While out for a drive today the electronic rev counter suddenly dropped to zero. While mulling the situation in my mind I noticed that the brake lights and separate circuit indicators had also failed. When I got back home, the wife confirmed the light failures while I sat engine running. I then pressed the garage door opener zapper on my ignition key ring and every thing jumped back to life! I can only imagine that the slight movement/vibration to the ignition key completed a circuit? Anyway, I was unable to reproduce the problem so no need for my minuscule tool kit (nothing) in the boot.

Very odd. I hate these issues. Very difficult to resolve the reasons.

Steve
Steve Gyles

Steve,


I had a similar issue last year while we were in Vancouver Canada. When I went over some rail tracks the car simply stopped running. I pulled over and was able to restart her. The second time we were on a bridge with no place to get out of traffic. In desperation I turned the ignition switch off and on and she immediately restarted on compression. The cutout occurred a few more times, but a quick jiggle of the ignition switch always did the trick.

Back home I tore down the switch, clean it up and reassembled. I also cleaned up the wire ends. Although the switch still feels somewhat sloppy due to wear, it seems to be working reliably again.

On the same trip I temporarily fixed a gas leak on the hose between the carbs with a bit of bubble gum (wife’s of course), a bit of rubber hose and a couple of clamps. That was good enough to get back the B&B. Fortunately the B&B owner had a Jag in the family so he was quite understanding. He was good enough to give me some epoxy which I used replace the bubble gum patch. That fix got me of the way back to Seattle. The fix was good enough that the epoxied hose is now in my spares. Epoxy and self-fusing waterproof tape (it only sticks to itself) are my recent additions to my small spares kit.

John
John Backman

Steve,
If I recall correctly, didn't you have a problem just recently with your "Ign" switch?

Regards
Colin
Colin Manley

Colin

You are right. Just checked the archives. "ignition switch Gremlin". It happened once while converting my indicators. At the time I had another wiring glitch which threw me off the ignition switch problem. I need to study the wiring diagram to figure out what is very intermittently (twice in a year) happening with the switch.

Steve
Steve Gyles

Hi Steve - my switch is also very sensitive to movement - especially over bumps - i think it is the key fob and 2 other keys dangling that set it off - will have to revert to the original leather tab. By the way - just seen a copy of the "Lightning Boys" in the local remainder bookshop.
Cam Cunningham

Cam

Good to know it's not just me.

I am Chapter 17 in the book and Chapter 1 in Lightning Boys 2.

Steve
Steve Gyles

If it were the ignition switch that would have to break the power to the live side of the fuse box which would cut the indicators and the brake lights, but also the power to the coil!
I wonder whether you have a dodgy connection elsewhere which is a bit sensitive to vibration. I've found that bullet connectors can go like that. A very likely candidate may well be the fuse A3/4 not seating cleanly through a bit of corrosion.
Graeme Williams

Another potential culprit is the two-fuse holder on the firewall. I regularly find the screws which take the wiring connections there work loose and need nipping up. Suggest you check if they are tight now. Likewise, the fuses can be loose in there and need the prongs bending to tighten things up. This assumes you have the standard fusing arrangement of course!
Bruce.
B Mayo

Graeme and Bruce

Everything under the bonnet is tight, clean and looking ok. All systems working fine. That's why I said that this sort of very infrequent happening is so frustrating. I just need to get my head under the dash to see if there is anything untoward.

Unfortunately, with my car in its current mod state it's not quite so easy always to refer to the standard wiring diagram for every connection. I have an alternator which has changed the connections through the control box as per Barney instructions; electronic ignition which has added a couple of wires; electronic RPM with its wires; and independent direction indicators with numerous new wires and connectors (the direction indicator relay box is there just for looks, no connections to it).

When the systems failed at the weekend I did wonder why the ignition system was unaffected - sort of ruling out the switch. I presume I had also lost the fuel gauge, but did not look at it under the key fob. Main lights, dips, fogs, wipers, hooter, heater fan were all still working. I was bemused that it was the garage door opener fob that appeared to fire it all back to life. It was instantaneous as I pressed the button!! Maybe something in the MGB electronic tacho?!!

Steve
Steve Gyles

This thread was discussed between 10/04/2016 and 12/04/2016

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