TR2/3/3A Red ignition light stays on...car has alternator not generator.

[karls59tr]

I just finished adjusting the valves on my TR3. Now the red ignition light is glowing when the car is running? After the valve adjust the idle stayed about the same so I don't think the valve adjust caused the idle to go slow enough to cause the light to stay on? I don't think it can be a voltage control box issue as most of that was bypassed when the conversion was done. What is the best way to track down the electrical issue?

 

[bobhustead]

Does it go out at higher revvs? Put a VOLTmeter on the battery and raise the revvs to 2500 and check the voltage. Should be 12.7 to 14.2 (closer to 14.2) if it is charging. How old is the battery? Perhaps have it load tested.
Bob

 

[karls59tr]

Very strange....when I started the car up today the red ign light did not stay on after start up? I installed a voltmeter in the dash when I converted to an alternator and it shows 13 when the car is running. That's a little concerning as I seem to remember it reading higher than that before. How do I know I'm not just running off the battery? Is there an easy way to test an alternator? Karl

 

[bobhustead]

If the voltage reading when running is higher that when shut off (thus reading battery alone), you are not running just off the battery. Best way to test the alternator is at an alternator shop or many parts shops can test if off the car.
Bob

 

[karls59tr]

If the voltage reading when running is higher that when shut off (thus reading battery alone), you are not running just off the battery. Best way to test the alternator is at an alternator shop or many parts shops can test if off the car.
Bob

Not sure I follow. The voltmeter reads 13 when I turn the key on but when the car is running the voltage does not climb up at all. Shouldn't the voltage rise up if the alternator is charging the battery?....go up to 14.2?

 

[DrEntropy]

Not sure I follow. The voltmeter reads 13 when I turn the key on but when the car is running the voltage does not climb up at all. Shouldn't the voltage rise up if the alternator is charging the battery?....go up to 14.2?

Short answer is: yes.

A VOM at he battery terminals is the best way to initially check things. Ignition off, should see 12V and a bit more. Engine running at off idle (as Bob suggests, over 2K+ RPM) you should see a voltage rise, from 12.5 to 13 at a minimum. If the regulator is working properly and VOM indication doesn't go over 13.5V the battery may be charged well enough that the regulator "sees" that. Can you turn on a load? Headlights? If so watch the VOM and see if it shows the regulator trying to compensate. Otherwise, take the alternator to a place that can test it with a load on it.

 

[karls59tr]

So I put a multimeter across the battery and it showed 12.6 and when I revved the motor It showed 14.7 so I assume the alternator is charging the battery. I am using a Smith's voltmeter in the dash but it shows 13 with the key on but will not show increase in voltage when the engine is revved? Anyone know what would make the dash voltmeter not show correctly?

 

[bobhustead]

The dash instrument is not working properly.
Bob

 

[DrEntropy]

Must be that the voltmeter is faulty. Are you taking the power to the instrument directly from the ignition switch? I've "added" a Smiths voltmeter to the MGB along with an alternator conversion, and it will indicate supply voltage just fine. Got it from Nisonger, matching clock, period correct face and bezel.

 

[karls59tr]

Must be that the voltmeter is faulty. Are you taking the power to the instrument directly from the ignition switch? I've "added" a Smiths voltmeter to the MGB along with an alternator conversion, and it will indicate supply voltage just fine. Got it from Nisonger, matching clock, period correct face and bezel.

Sounds like I have a similar voltmeter i got from Smiths as it it looks a lot like the existing gauges.What puzzles me is that I've had the unit for several years and it has always given me correct readings up until now? I am taking power from the ignition switch and ground from one of those brass wing nuts that attach the backing plate. i found a spare aftermarket gauge in my parts bin that tested good on the battery itself that i was thinking of installing but it does not match up with the other gauges and it stands out as not correct. I was hoping i could try and find out what is wrong with the Smiths gauge.

 

[DrEntropy]

Sounds like I have a similar voltmeter i got from Smiths as it it looks a lot like the existing gauges.<snip> I was hoping i could try and find out what is wrong with the Smiths gauge.

Hope you do! I'd likely disconnect it and put it directly to the battery and see if there's a change as the RPM's come off idle.

 

[karls59tr]

Hope you do! I'd likely disconnect it and put it directly to the battery and see if there's a change as the RPM's come off idle.

Good idea. I'll give that a try.

 

[karls59tr]

Very Strange. I cleaned up the brass eyelet connectors at the ends of the wires with sandpaper till they were shiny. I secured the wires of the Smiths voltmeter gauge to the battery posts and the needle swung to 12.9. I fired up the engine and when it was warm I revved to 2500-3000 rpm but the gauge needle would not go past the 13???? What's up with that?

 

[Sarastro]

Sounds like the voltmeter is sticking at 13V. A common problem.

Now, back to the ignition lamp. It is connected between the battery and a point in the alternator that generates approximately the battery voltage when running. If the alternator is not generating output, that point is 0V and there is ~14V across the lamp, so it goes on. My guess is that the alternator is working but the connection on one side of the lamp is somehow grounded. Make sure all the connections are good.

Also, it's best to do the tests suggested by Dr. E with an analog meter. The digital meters can be upset by electrical noise in the car's electrical system. But since you are seeing a sensible voltage, 14.7V, it's probably OK. Usually noise causes it to give nonsense indications.

 

[karls59tr]

Sounds like the voltmeter is sticking at 13V. A common problem.

Now, back to the ignition lamp. It is connected between the battery and a point in the alternator that generates approximately the battery voltage when running. If the alternator is not generating output, that point is 0V and there is ~14V across the lamp, so it goes on. My guess is that the alternator is working but the connection on one side of the lamp is somehow grounded. Make sure all the connections are good.

Also, it's best to do the tests suggested by Dr. E with an analog meter. The digital meters can be upset by electrical noise in the car's electrical system. But since you are seeing a sensible voltage, 14.7V, it's probably OK. Usually noise causes it to give nonsense indications.

I should have mentioned that the ignition lamp is no longer staying on. It goes out once the engine starts. My concern now is why would the voltmeter gauge stick at 13 when it is installed in the dash but when the gauge is removed and wired 'directly to the battery' it does not stick at 13 but will show higher voltage when the engine is revved? This is a newer Smiths voltmeter that I replaced the ammeter with when I did the alternator conversion a couple of years ago. It.s been trouble free up until now What causes the voltmeter to stick at 13 when it is mounted in the dash?

 

[karls59tr]

I guess "stick" is the wrong term. I should have said "stays" at 13. The voltmeter gauge works fine when it is not in the dash but tested out of the car. This voltmeter is not an old unit. It is fairly new and has worked flawlessly until recently.

 

[DrEntropy]

Are you SURE you're connecting the gauge to a WHITE wire from the switch and NOT a GREEN one?

 

[karls59tr]

Well I pulled the gauge consul out to have a look and found that the brown/ white thick wire and thick brown wire had melted against the black wiper motor switch ground button wire. I joined these two wires together when I did the conversion to the alternator as per British Wiring kit instructions. I found the instructions for the kit and it says to join the the thinner brown/blue wire to the thinner brown /white wire. That connection looks alright. But there is no mention of joining the plain brown thicker wire toto the thicker brown and white wire? I may have screwed that up but I'll have to double check with British Wiring.