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MG TD TF 1500 - ignition light & ammeter

I'm a relatively new (6 mo.) owner of a 1952 TD. My ignition light does not illuminate when I turn the ignition key to the "on" position. When I start the car, the light comes on and, the faster the engine revs, the brighter the light gets. I am sure that my generator is working because my battery has not drawn down since I bought the car and I have driven it relatively frequently. Sometime in the past, the wiring loom was replaced with a homemade version. None of the wire colors in the loom match the wiring diagrams in the manuals. In fact, every wire under my dashboard is yellow.

I believe that the wiring is not correct to the ignition light and that, because of this, it is working just the oposite of the way that it should. Is correction of this problem likely to be as simple as switching the wires on the light?

Oh, yeah. The ammeter has been pegged at 0 since I got the car and doesn't move. Don't know if this is related or not.
NHW Wilson

BHW,

Unfortunately, switching the wires at the light won't have an effect.

Check and make sure your ignition lamp wire is connected to terminal "D" on the voltage regulator. (From your description above, I would say you need to replace your wiring over the winter.) Next I would check to see if the generator leads are connected to the correct terminals on the genny and the regulator. The large wire yellow-green should be on terminal "F" and the large post of the genny. The smaller yellow wire should be on terminal "D" and the small genny post. Your light is working as if it is connected to the yellow-green generator output.

On the ammeter, it should show a negative reading when you turn the headlights on. If there is no deflection, its either wired wrong or bad. Check and see if it is wired between the hot side of the starter switch and terminal "A" of the voltage regulator. If it is, the meter is likely bad.

Let us know what you find!

Good luck,
Evan

Evan Ford - TD 27621

I would suspect the connections to the regulator. the ammeter should be between the battery hot lead on the starter switch and terminal A on the regulator.

The ignition lamp should be between the D terminal and the switched terminal on the ignition switch.
It sounds like you have it between D and ground so it is reading the generator output voltage rather than the difference between generator and battery.

I agree with above rewire at the earliest oppertunity.
Don Harmer

Hello NHW -- Evan got a typo in his response to you, the orig. yellow/green wire goes to the smaller terminal on the genny(field), the larger wire, yellow, goes to thelarger terminal on the genny(armature). Since your car has been rewired with non-standard colors you will have to disconnect at least one end of wires to make sure you are not measuring contenuity thru other parts of the circuit.

As you check continuity it might be smart to put a label on each wire with the color code it is supposed to have.Yellow is 25 for instance. This will help trouble shooting until you can get a harness with the correct colors installed.

Contact me if you have further questions.

Bob
R. K. (Bob) Jeffers

Thanks for your help everyone! New wiring harness is on my list for this winter. I will let you know how I come out with the ignition light. By the way, I guess I didn't fill the form out properly when I signed up. For some reason, my initials insist on appearing by my last name. My first name is Nelson. It was nice chatting with you.

Nelson (TD Mark II, 11793)
NHW Wilson

Welcome to the BBS Nelson.

Evan Ford - TD 27621

Hello Nelson
You should join one of the local MG clubs and have a tech section in which you and your local club members install your new wiring harness. Sounds like a good time in the making. John
John Hambleton

I'll piggy back on this thread with a similar problem: My ignition light behaves properly but the ammeter pretty much just stays at 0, no matter what. There is very slight movement when the fuel pump is ticking, so I know its getting some juice. Before I got a new voltage regulator the ammeter would read +15 amps when going up a hill or revving the engine. Is a consistent "0" ammeter reading "normal/acceptable"?

Bryan
52 TD Mk II
B Sieling

I have a fair bit of movement... when i accelerate it climbs then drops back a bit...with lights on it drops until i get the revs up... with lights, brakes and signals it drops all the way (my third brake light seems to draw a lot)...and then climbs when i rev.... seems to be a lot of plus/minus movement.
When i got the car it was stuck in the plus side and never moved... took off the bezel and found the needle stuck to the dial face (not sure how that happens even in a barn)... anyway... the needle is really fragile and it was hard getting back together and working....
gordon lawson - TD 27667

This thread was discussed between 20/10/2005 and 24/10/2005

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.