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MG TD TF 1500 - Generator or Voltage Regulator, how to diagnose

First the good news. I got my TF started today, for the first time since I've owned it(> 3 years). It started right up, and ran great. I ran it in for 20 minutes at 2000 rpm to bed in the cam, and I feel great about that. Except for a minor coolant leak caused by a loose hose clamp and a minor electrical problem, everything went great.

Now about that electrical problem. The ignition warning lamp does not come on when the key is turned on, but comes on when the car starts, and glows dimly when the car is idling. It gets much brighter when the car revs, but seems to occasionally blink off.

I thought this might be due to the previous owner converting to negative ground, although I don't know whether or not it was, since I don't have much history on the car and it was not running and had no battery when I got it.

I tried polarizing the generator by making an intermittent contact with a (-) hot wired jumper on the field coil, as recommended on several sites that show how to do this. This didn't make any difference in the behaviour, the ignition light still acted the same.

I think the generator is charging, because the ammeter registers + 15 amps or so when the car is at 2500 rpms, and I'm fairly sure the ammeter is wired correctly since it ticks a few amps negative when the fuel pump clicks. So it may be the regulator. I'm going to test the voltage sometime tomorrow when the car is running, but I'm too tired right now.

So how do I test this? I'm tempted to just order a regulator from Moss, since it's relatively cheap, and might fix the problem. If that does not work, then I can just order a generator, or try to get mine fixed.

Any ideas?
Mark B.

Congratuations... great feeling to hear it actually run for the first time isn't it? (Will never forget mine first starting).
Don' t know about the electrical probem... my light stayed on until I cleaned the generator... yours sounds different.
gordon lawson

Thanks, Gordon. I figured it out. I had the indicator bulbs for the low fuel light and ignition reversed. Now that the bulbs are in the correctly wired circuits, it functions correctly. The order of the indicator lamps in the wiring diagram are different than their actual physical order, and I got confused. It's electrically correct now, although I now have the ignition warning lamp on the left instead of the center, with the jewels reversed for the fuel and ignition indicators.

While the blue indicator looks pretty cool, I think I'm going to correct it as soon as I have time. I really hate working on the dash after it's installed, though, those little sockets are really hard to get to.
Mark B.

Congrats on the first start Mark!
Nothing like the first tyme you hear that lil' 4 banger purrr! Can't wait to hear mine again ....she a pile of pieces right now.
Cheers,
David 55 TF1500 #7427
David Sheward

Mark...

This was on an earlier thread... however, if I read your post right I think your lights might be in the wrong place?
http://www3.sympatico.ca/gordonblawson/td/td102.jpg
The three warning lights from left to center:
Red ignition light, Green fuel warning light, Red turnsignal light.

Not sure if that is how yours is or not.

I have found that while driving, the turn signal light in the middle is covered by the steering wheel.. have thought about changing the ign and signal lamps so I can catch it if I leave it on....

In my photo the ign is hidden by the wheel.
gordon lawson

Left to Right the TF has: Blue Low Fuel Light - Red Ignition - Green flashing Indicator Light.
John James

Yes, Gordon, I now have the lights in the wrong order. The jewels are correct (blue, red, green, from left to right), but now the ignition is on the left (blue) and low fuel light is in the center (red). I'll have to fix the wiring to the sockets later, since both of these sockets are isolated from ground. I wired the low fuel light so that the socket was hot and the current return is through the bulb.

That might be kind of backwards, but it works, so long as the socket does not short out, causing major damage to the harness. There's a similar situation with the ignition light, and both sides of the ignition light circuit are hot and capable of delivering lots of current. Now that I think of it, I may put a small fuse into each lead that feed the hot sockets while I'm changing them over to the correct one.
Mark B.

When the socket wiring is correct on the low fuel lamp grounding the socket causes no disaster, the low fuel lamp simply lights.
If not grounding connecvts the switched side of the ignition switch to ground...instant disaster.

The socket side of the ignition lamp should go to D on the regulator.
Don Harmer

Thanks for the help, Don. I somehow managed to get both of those backwards and on the wrong socket, to boot. I see a dashboard pulling in my future, since it's just about impossible to do it from underneath.
Mark Barrington

Mark, which terminal of your battery is connected to ground? Your first posting sounds as if you've polarized your generator to provide a negative output voltage, i.e., positive ground.
Bud Krueger

Yes, positive earth.
Mark Barrington

Mark,
When in doubt....FUSE IT!
I highly recomend fusing to the headlamps for sure... that is one of the highest amperage "loads" in the whole car..so is one of the best/worst chances of a harness fire! Please tell us you have fitted the little darling with a fire extingusher!
A "cut-off" at the battery is not a bad idea either.
Best Regards,
David 55 TF1500 #7427
David Sheward

can anyone help me. i was replacing the sidelight bulb on my 1999 mgf and somehow managed to short it out. as a result the front and rear nearside side lights have went out and also th dashboard lights. ive checked the main fuses but they are ok and the offside lights have not been affected.
graham foley

Graham - You need to post this querie on the MGF BBS. If it is any later than 1955, nobody here knows anything about it (or at least nothing they will admit to) ;) Cheers - Dave
David DuBois

This thread was discussed between 14/02/2005 and 01/03/2005

MG TD TF 1500 index

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