Vixen electrical issue - help please
Discussion
Sitting outside the local Post Office yesterday with the car idling, suddenly the engine cut out and grey smoke filled the space behind the rev counter glass (inside the rev-counter only). Immediately turned ignition off, smoke cleared. Tried turning the engine over again, would not start and smoke re-filled the rev-counter.
Investigation shows no signs of any melted wires or other indicators of any problem apart from I had fitted an in-line fuse between the starter solenoid & dizzy. This had blown. I replaced the fuse and it immediately blew on turning engine over.
So (I am a numpty with electrics) does this indicate what the fault is ? Starter solenoid or coil as the obvious candidates but all the tests I can find for solenoid only test for working or not (engine turns over fine). I am presuming that the Accuspark electronic ignition unit in the dizzy will have been fried so I don't want to try a replacement coil until I can determine the cause as I don't want to fit a new Accuspark unit just to fry it again.
I am presuming the smoke in the rev-counter was caused by excessive voltage dumped down the wire from the coil + post to the rev counter. Could either the coil or solenoid fail in a way that dumps excessive voltage down this wire?
Thx
Moto
Investigation shows no signs of any melted wires or other indicators of any problem apart from I had fitted an in-line fuse between the starter solenoid & dizzy. This had blown. I replaced the fuse and it immediately blew on turning engine over.
So (I am a numpty with electrics) does this indicate what the fault is ? Starter solenoid or coil as the obvious candidates but all the tests I can find for solenoid only test for working or not (engine turns over fine). I am presuming that the Accuspark electronic ignition unit in the dizzy will have been fried so I don't want to try a replacement coil until I can determine the cause as I don't want to fit a new Accuspark unit just to fry it again.
I am presuming the smoke in the rev-counter was caused by excessive voltage dumped down the wire from the coil + post to the rev counter. Could either the coil or solenoid fail in a way that dumps excessive voltage down this wire?
Thx
Moto
Thx guys.
I don't have a ballast resistor though. The car has always run a non-ballasted coil with a live wire direct from the starter solenoid to the coil. I guess this may have been changed from standard by a previous owner.
I have shone a torch up behind the dash and followed the white wire from the rev counter through the bulkhead to the coil and the white & blue wire from the coil to the solenoid and no signs of damage.
During the week I'll take the rev counter out to check thoroughly and also check the ignition wire that loops across the back of the dash. Yes I did have a copy of your wiring diagram thanks - spent yesterday using it to get my head around what wires are what. Very useful thx.
By the sound of it I get the impression that this is most likely a wiring fault as nobody suggests a fault in the coil or solenoid could have caused it. Is that correct?
Moto
I don't have a ballast resistor though. The car has always run a non-ballasted coil with a live wire direct from the starter solenoid to the coil. I guess this may have been changed from standard by a previous owner.
I have shone a torch up behind the dash and followed the white wire from the rev counter through the bulkhead to the coil and the white & blue wire from the coil to the solenoid and no signs of damage.
During the week I'll take the rev counter out to check thoroughly and also check the ignition wire that loops across the back of the dash. Yes I did have a copy of your wiring diagram thanks - spent yesterday using it to get my head around what wires are what. Very useful thx.
By the sound of it I get the impression that this is most likely a wiring fault as nobody suggests a fault in the coil or solenoid could have caused it. Is that correct?
Moto
The tacho is out and there is a very strong 'burnt something' smell coming from inside, so I'm guessing an internal component is definitely deceased.
The good news is that all the wiring seems to be in good order.
Still unsure about the car cutting out suddenly. I can only assume that a voltage spike killed the Accuspark EI. They are very sensitive to this. Whether a tacho failure could cause this though ???
I'll send the tacho off for repair and see what diagnosis they offer.
Moto
The good news is that all the wiring seems to be in good order.
Still unsure about the car cutting out suddenly. I can only assume that a voltage spike killed the Accuspark EI. They are very sensitive to this. Whether a tacho failure could cause this though ???
I'll send the tacho off for repair and see what diagnosis they offer.
Moto
Decided to strip the tacho just to see for myself what damage had occurred.
You can clearly see the ignition loop wires wrapping twice through the toroid having been fried. So I'm presuming they must have shorted at that point due to deterioration of the wires sheath. I guess they're probably 45 ish years old.
It has also melted the one end of the winding wire.
Hopefully it can all be repaired.
Moto
You can clearly see the ignition loop wires wrapping twice through the toroid having been fried. So I'm presuming they must have shorted at that point due to deterioration of the wires sheath. I guess they're probably 45 ish years old.
It has also melted the one end of the winding wire.
Hopefully it can all be repaired.
Moto
RCK974X said:
You can do a cheap repair yourself first.....
That burnt wire is only a simple loop through the coil unit, and you can use a roughly similar piece of wire to repair it.
OK, you may not have the right ends, but it should work with anything (like replacement spades).
Also what you have there is an old style 'current pulse' trigger tacho, which often does not work right with modern electronic ignitions.
So if you are sending it away anyway, consider getting the innards changed for a 'voltage pulse' trigger circuit instead.
(yes you can keep original dial and needle and all the mechanics, you just get a new circuit board inside).
Even though the actual short is probably somewhere else, that wire was the 'weakest' piece (=> the loop means it would heat up first...), but do check it didn't catch
on the case of the tacho somewhere..... if not, then you've got more detective work ahead !
If you did have some kind of ignition amplifier /electronic ignition added, then that unit could have failed and presented as a short across the battery, although it would be unusual if it didn't also get very hot (so will be stained/marked).
Otherwise, favourite is still a wire (or a couple) which has rubbed/ broken insulation somewhere to cause the short.
I was going to do as you suggest & replace the ignition wire myself until I noticed the winding wire end had also melted & broken. In the photo you can just make it out. I don't have the tools to attempt to repair such a fine wire and reattach it to the blue blob thing (I have no idea what it is).That burnt wire is only a simple loop through the coil unit, and you can use a roughly similar piece of wire to repair it.
OK, you may not have the right ends, but it should work with anything (like replacement spades).
Also what you have there is an old style 'current pulse' trigger tacho, which often does not work right with modern electronic ignitions.
So if you are sending it away anyway, consider getting the innards changed for a 'voltage pulse' trigger circuit instead.
(yes you can keep original dial and needle and all the mechanics, you just get a new circuit board inside).
Even though the actual short is probably somewhere else, that wire was the 'weakest' piece (=> the loop means it would heat up first...), but do check it didn't catch
on the case of the tacho somewhere..... if not, then you've got more detective work ahead !
If you did have some kind of ignition amplifier /electronic ignition added, then that unit could have failed and presented as a short across the battery, although it would be unusual if it didn't also get very hot (so will be stained/marked).
Otherwise, favourite is still a wire (or a couple) which has rubbed/ broken insulation somewhere to cause the short.
Edited by RCK974X on Tuesday 25th December 02:17
Also as I'm unsure as to any other damage to capacitors / resistors etc it needs to be checked & tested.
Thx for the info about changing to a voltage pulse trigger circuit. I'll speak with Smiths repairer about that.
Cheers for all the advice guys, will update you when I've made progress. Have a very Merry Christmas Day.
Moto
After many unsuccessful hours spent tracing the wires along the loom and behind the dash, I decided the time was right to completely rewire the car. It had been on my wish list for a while as the original wiring was not great and a major issue was inevitable at some point.
A quick call to a local chap and 2 weeks later the car is done. The only original wiring left is the aerial cable and the interior light wire behind the roof lining.
I've had a few mods - a cut out switch now replaces the cigar lighter, a manual over ride switch on the engine fan and a dash light to show when on, wiring taken to behind rear trim for a rain light incase ever required, fully fused for each consumer unit, dynamo replaced with an alternator (so voltage stabiliser also gone) and a push button starter solenoid mounted in the engine bay drivers side so I can easily crank the engine when working on it.
Oh, and the tacho repaired and modified for electronic ignition.
All in a tidy job.
A quick call to a local chap and 2 weeks later the car is done. The only original wiring left is the aerial cable and the interior light wire behind the roof lining.
I've had a few mods - a cut out switch now replaces the cigar lighter, a manual over ride switch on the engine fan and a dash light to show when on, wiring taken to behind rear trim for a rain light incase ever required, fully fused for each consumer unit, dynamo replaced with an alternator (so voltage stabiliser also gone) and a push button starter solenoid mounted in the engine bay drivers side so I can easily crank the engine when working on it.
Oh, and the tacho repaired and modified for electronic ignition.
All in a tidy job.
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