Ignition light on

[Hamish]

Hi

Did a great track day in my 1959 TR3a at castle Combe today. 70 plus miles of full on pace even in the wet. No wipers as I had flyscreens.

 

But my ignition light is now permanently on what ever the engine revs. The ammeter shows discharge too.

 

Im still running the dynamo not alternator.

 

I dont understand electricery are there any simple checks a numpty can try ?

 

H

[Ben Freer]

I'd let the poor thing dry out first Hamish! It might - just might, self-rectify itself!

[John McCormack]

Agree, let it rest for awhile. The Prince of Darkness sometimes lets you off with a scare.

 

If it persists check all the battery, generator, earth and regulator wires are clean and tight. Do this anyway.

 

Then put a multimeter on your battery with the engine at 2000 revs, it should show above 14.5-15 volts. If it reads 12-12.5 volts it isn't charging at all and if above 12.5 and less than 14.5 it isn't charging properly.

 

If it isn't charging or not properly, put one lead of the multimeter lead to earth somewhere on the engine (e.g. head stud or bellhousing bolt) and the other on the big cable from the generator. If it is reading 14.5 or higher the generator is charging so it is probably the regulator.

Edited April 5, 2018 by John McCormack

[iain]

More than likely a loose/wet/damp connection on the back of the dynamo.

 

Iain

[Lebro]

Or worn out brushes, or bad / dirty contacts in the regulator.

 

Bob.

[littlejim]

Not in a TR, but have seen a situation where an ancient ignition light bulb caused a similar problem.

[Hamish]

 

 

 

 

Then put a multimeter on your battery with the engine at 2000 revs, it should show above 14.5-15 volts. If it reads 12-12.5 volts it isn't charging at all and if above 12.5 and less than 14.5 it isn't charging properly.

 

 

 

If it isn't charging or not properly, put one lead of the multimeter lead to earth somewhere on the engine (e.g. head stud or bellhousing bolt) and the other on the big cable from the generator. If it is reading 14.5 or higher the generator is charging so it is probably the regulator.

Thanks for the test tips.

 

Earths ok

Inc some temp ones for test purpose engine / chassis to battery.

 

Its all dry

In fact is very hot at the back of the dynamo but has shielding. So doubt the dynamo would be wet.

 

No charge at battery terminals.

 

And the big yellow wire out the back of dynamo measured with earth to head is 2. 8 v ish

 

So I presume dynamo ?!?!

[RobH]

First look at the thinner wire which is the field connection on the dynamo. That should go back to the F terminal on the regulator. Check you have continuity between those two points. The dynamo needs 'excitation' current via that wire to function.

 

If that's OK then check the brushes as Bob suggested above.

Edited April 5, 2018 by RobH

[Hamish]

First look at the thinner wire which is the field connection on the dynamo. That should go back to the F terminal on the regulator. Check you have continuity between those two points. The dynamo needs 'excitation' current via that wire to function.

 

If that's OK then check the brushes as Bob suggested above.

Set to 200ohm I get a resistance (?) of 14.5.

 

The fat yellow wire measures 23 doing the same test D on regulator to dynamo connection

 

So is that dynamo out and clean up / brushes etc.

 

Is now the time to go to an alternator????

Edited April 5, 2018 by Hamish

[RobH]

Did you disconnect the wire from the dynamo before making that measurement? If not, try again with it off end-to-end on just the wire to check the wire itself is OK. The reading you got is high - what does the meter read with the probes shorted together?

Edited April 5, 2018 by RobH

[Hamish]

Hi Rob

 

Thanks for the advice. As you can tell I am a real novice when it comes to electricery.

 

I did not disconnect the wires from either end.

The dynamo connections are very hard to see because of old 4 branch manifold exhaust and a heat shield.

 

Ill have to have another look at the weekend now.

 

If anyone has any pointers I need to try ( in very simple terms !!) all in one go I would apperciate it.

 

Just for completeness I already have - neg earth conversion and the narrow belt conversion.

 

H

[Ian Vincent]

Check that there isnt a short in the field coil on the dynamo causing the regulator to cut out.

 

Rgds Ian

Edited April 6, 2018 by Ian Vincent

[Hamish]

Check that there isnt a short in the field coil on the distributor causing the regulator to cut out.

 

Rgds Ian

A short what ??

[RobH]

Before you make any resistance measurements you need to connect the meter probes together. It ought to read zero. If it doesn't, either adjust the meter to zero (if it's got an adjustment control) or note the reading and subtract it from the measurements you make.

 

 

You probably won't be able to do the check Ian has just suggested ( I think he means dynamo not distributor). The reading to earth will be very low anyway (<10 Ohms) and you need special test kit to check for shorted turns.

 

This site shows some basic voltage checks you can do. https://www.howacarworks.com/electrical-systems/testing-a-dynamo-and-checking-output

If you run the engine with the dynamo connections shorted as they show, do make sure you do not rev the engine beyond a slow idle as that will generate a higher voltage which may damage something.

[Ian Vincent]

Correct, I did mean dynamo, sorry about that. I only suggested it because I had that happen to me once and it took a while to find it. In the end I took the car to an autoelectrician and he found the problem.

 

Rgds Ian

Edited April 6, 2018 by Ian Vincent

[Hamish]

Hope to get on this later.

Off out shopping for wedding rings and a grooms suit !!!!!

 

Watch this space. Car update stuff obviously !!

As I will need more electricery advice.

[Hamish]

Ok a mixed day.

Plus side (Suzie - my better half and I ) bought our wedding rings

[RobH]

Well that's a dilemma. If you've got to tear it down anyway there are advantages with an alternator unless you want to keep originality. The complication is if you don't already have a narrow fan-belt conversion. You can use an alternator with a wide belt by re-using the dynamo pulley, though it's not optimum because the speed is lower than it should be so you don't get the full benefit of higher charge at idle.

 

If you decide to retain the dynamo then yes - while you've got it out and if there's no fault in the wiring new brushes might save more work later.

 

You might be able to check the dynamo operation while off the car if you can spin it with an electric drill, so you know its good before replacing it.

[Lebro]

Why not just measure the field resistance from the other end of the wire - where it goes into the regulator on "F"

(disconnect from "F" first)

 

Bob.

Edited April 7, 2018 by Lebro

[Don H.]

I'm not crazy about the condition of those connectors, Hamish. Definitely worth a moment to make sure they have bright metal-to-bright metal contact. It's amazing how many electrical problems are bad connections in the end -- Occam's Razor at work.

[brenda]

H I would find the fault first before you change to a alternator,electric on a car is a pain you could have cooked the rear of you dynamo, I have a dynamo off my car you could try if you like.

 

Mike

Redrose group

[Z320]

Hi Harmish,

 

the rear bearing of the dynamo is only a bronze bush.

It needs some oil from time to time AND the fan belt must not be to tight.

Otherwise the rotation shaft destructs the bronze bush and you loose electrical contact.

 

It that is the case and you drive on next the shaft damages the aluminium rear shield of the dynamo.

That's only a few miles later.

 

If there is attention of the driver for that the dynamo does a great job ????

 

Good luck

Marco

Edited April 8, 2018 by Z320

[Hamish]

Thanks Mike thats kind of you

I may take you up in that.

 

I suspect its the brushes have worn then finally failed.

 

The car has been running and competing brilliantly over the nearly 2 years Ive had it and many years before that by P.O. in its current set up of dynamo/ heat shield/ exhaust etc

 

Perhaps the 70 odd track miles, thus fairly sustained higher revs on Wednesday was a shock to the system for the poor thing.

 

Ill have to bite the bullit and strip down that side of the engine and get the dynamo out as my first championship round is 5th May.

H

[brenda]

H. It’s in the boot of tr if your at the meeting today if not we can meet and you can check it fits no rush for it back as it’s on a shelf in the garage with all the other bit and bobs.

 

Mike

Redrose group

[Hamish]

Cheers Mike

 

Ive ordered a repair kit but borrowing yours could be a great diagnostic tool.

 

Not sure Ill be at meet - in favour of spanner work ????