Voltage regulator/electrical mystery

[houseamber]

Hello lovely people,
So here we go again with a new mystery!
Our 1962 Morris has developed a strange issue, the symptoms of which are:

Starts as normal until you turn on the main lights or indicators and then it dies
Terminal A on the voltage regulator feels hot at this point
After a few minutes it will start up again and repeat the cycle

It has an alternator

Any ideas? Bad earth or knackered voltage regulator? Or something else?

Thankyou
Amber

[philthehill]

The voltage regulator is bypassed when an alternator is fitted.
The alternator has its own built in regulator.
There is a revised wiring diagram relative to the fitting of an alternator on this site - just use the search facility.

[houseamber]

Thank you - it's definitely still wired in and getting hot at terminal A.
I presume therefore that as we have an alternator the voltage regulator is in effect not doing anything and therefore it must be a bad earth?

I'll have a look at the wiring diagram in case it sheds any light on the issue

Thanks again

[oliver90owner]

I think a multimeter, to check voltages as the fault develops might well be a good indicator of what is happening.. Quite likely someone will be along shortly to tell you how to do a similar check with a test lamp.

Likely you have an unwanted ‘voltage divider’ in your system which, as the resistance heats up, is reducing the current available to the ignition system, which may be running at lower than peak voltage already.

I have never included a dynamo type voltage regulator in the system, when fitting an alternator. They are not present on a modern vehicle, so are simply not required, once an old vehicle is upgraded to an alternator charging system. Many leave them in situ but to use the connections in the wiring harness. I would not do that because the available current from the alternator may easily be double the original wiring was designed to cope with

PTH’s suggestion is the way to go. More likely to be a bad connection in the supply than an earth fault, I think, but that depends on whether the lights are working when turned on.

[les]

viewtopic.php?f=11&t=39514
Don’t get too bogged down with science. Just check your system with the diagram in the link.

[oliver90owner]

It’s OK les. I did also send the poster a PM.

I was expecting a reply from the other person that does not think a lot..

[les]

Don’t be reluctant to name him, if he doesn’t think, he won’t be hurt !

[geoberni]

I'm intrigued/confused by this fault description.

Starts as normal until you turn on the main lights or indicators and then it dies
Terminal A on the voltage regulator feels hot at this point
After a few minutes it will start up again and repeat the cycle

It has an alternator

So you can start it, and it will happily sit there idling, until you touch the headlight switch or indicators, and that causes it to stop running?
At this point the connection at Voltage Regulator A is hot.

I am wondering if operating the headlights/indicators is a red herring and the car would 'die' anyway?

I'm thinking the car is 'dying' because the alternator is having such a load applied to it, the engine can't cope with turning it, so it's stalling. That would tie in with the cable at A being hot, a massive current going through it.
But the problem there is what route the current is taking to complete the circuit. Why is the wiring not a molten mess?


I certainly wouldn't consider starting the car again or even turning the ignition on, until some more passive investigation has taken place. I'd first be looking for any signs of burning (arching) or other wiring defects.

It's not a 'Bad Earth' a high resistance connection causes less current to flow, not more.
There is only one thing that causes an engine driven generator to stall and that is a massive electrical load, i.c. more current being demanded of the generator.
Think of it like going up hill without changing down the gears or increasing the fuel to the engine, the 'load' on the engine makes it slow until it stops.

What's the background to the car, has it been a recent runner or are you recovering it from being off road a long while?

[kennatt]

is this a new fault, as above was it running ok etc. How low is the tick over speed ,when it cuts out is it when you have the clutch down and then put lights on.The hot terminal may be a red herring.Curious fault. Can't think of where there would be a couple of resistors to set up a voltage divider ,unless one in alt and one in old regulator box.Vey strange

[houseamber]

Thank you for all for your responses. To answer some of the questions posed:
The car has been in our ownership for several years and driven a lot, though out of our Morris's it is the one that has had the least restoration work/renovation but that is more because it was in a pretty good state when we got it.
It is a new fault.
Whilst I was working today my other half went and cleaned and tightened all the connectors on the control box and cleaned the inside of the control box. He found a bad connection behind the dash related to the indicator stem which he redid.
The fault now seems to have resolved and connector A is no longer getting hot.
It's certainly a puzzling one!
If that has solved it, that's even more puzzling!