MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Generator / voltage regulator problem

In the early stage of checking the generator and voltage regulator, not wiring the car yet. I've connected the generator, fuel pump, coil, ground, ignition and ammeter to the regulator, no lights horn, ect. When I rev the engine the voltage going to the battery continues to climb up to 16 volts and higher at wot. That seems excessive to me. The second problem is when I turn on the ignition key the fuel pump starts and current flows to the coil but when I turn off the ignition the engine continues to run. I realize this could be a complicated problem but I thought someone might have a simple solution. Thanks

Tim
TD12524
TW Burchfield

Tim, what do mean by ' not wiring the car yet'? Are you using the wiring harness, except for the lighting, horns and wiper circuits? Or, have to point-to-point wired the networks? Bud
Bud Krueger

Bud, point to point using individual wires not the harness. After doing some reading I think the 16 volts is acceptable and I now know how to adjust the output with the car running. But I'm stumped as to why the car continues to run after the ignition is shut off. I have the coil, fuel pump and the Gen Output wire D (generator to regulator regulator to ign) connected to the ign post on the ignition wire. Post A is connected to one side of the ammeter and the other side is connected to the hot side of the ignition switch. A1 is connected to position A on the ignition switch. I do not have the ignition warning light installed. I've tried 2 regulators and each one charges but the car won't shut off when the ignition switch is turned off.

Tim
TW Burchfield

16 Volts is close (I think) but may be too high for sustained highway type driving. The easy adjustment (if it is a bit too high) is to turn on your headlights for daytime driving. Otherwise, there is an adjusting screw and a locknut on the backside frame of the regulator. Regulator has less windings on its coil than the cutout coil. See page 13 here for info.

http://mgaguru.com/mgtech/books/lts_otcc/Session5_GeneratorControl.pdf

As close as 16 volts is to 15 or 15.5 volts, the adjuster screw will likely only need to be turned about a 1/4 turn. I suggest you leave alone the "air gaps" for now.


D mckellar

D mckellar, thanks. I looked at a few You Tube videos and saw what you are referring to. Any idea why the car continues to run after I turn off the ignition switch? I didn't let it run too long. Maybe there is some residual current in the system?

Tim
TD12524
TW Burchfield

Tim, it sounds like you are still getting voltage from the generator when you turn the ignition switch off enabling the motor to run. Maybe when you finish wiring up it will work correctly. Checking generators years ago without an amp. meter you would start the engine then disconnect the battery, if it still ran then the generator was working.
Regards, Don TF 4887 "Figaro' TC 1736 "Sibelius'
Don Walker

Thanks for posting the Lucas booklet: it will fit nicely in the new building I'm putting up to store all the Lucas, SU, MG, etc, literature I continue to accumulate from reading car forums.
T W Moore

Tim- One side of ammeter (A) goes to A of regulator. A1 on regulator is connected to A of ignition switch. I think you might have this mixed up.

The other side of ammeter (B) should only go to the starter motor and to something like panel lights, not to anywhere on ignition switch. A much bigger cable also goes to starter motor- from the battery.

2 wires should be coming off IG of ignition switch. One goes direct to A3 of regulator, and another wire comes off A3 to feed coil, fuel pump. The other wire coming off IG goes go to D of regulator, but first goes through the resistance wound ignition warning light.

I dont have a TD diagram handy, but these are mostly similar. A bigger diagram may be helpful, heres is a TC, which should be the same for the things you have wired. Double check first, of course.

https://fromtheframeup.com/uploads/TT_EL972_Wire_Diagram_TC_EXU.pdf



D mckellar

16 V will be too high for the battery and for the dynamo itself. Please adjust the regulator after correct wiring to get a voltage of 14,3... 14,6V.
W. Mueller

Have a look at healey6.com/bulletin.htm this will give you all the info you need on your electrics.
PS download but do not print as it is massive
Ray TF 2884
Ray Lee

D mckellar, sorry in my rush to post I typed, "Post A is connected to one side of the ammeter and the other side is connected to the hot side of the ignition switch." I should have said, "...hot side of the starter switch." Thanks for catching that.

W. Mueller, I will adjust the voltage at half throttle to 15 v as a starting in point. Thanks.

Not sure if it will make a difference but I'll install the gen warning light this morning.

Thanks everyone.

Tim
TW Burchfield

Just in case anyone is wondering why I am doing this rudimentary wiring: I have finished the engine, chassis, brakes, shocks, etc. I am test fitting the body before paint and I want to drive the car before I officially say the chassis et al are finished. Once the body is back off I'll start installing the wiring harness. Thanks again for all of the suggestions.

Regards

Tim
TW Burchfield

I had a strange problem like that with a Jag xk140. I had installed a new electric fan on front of the radiator. When turning of the ignition switch the engine would continue to run for about 30 seconds and then slowly shut down.
If the fan was turned off the engine would shut down immediately.
It was the fan becoming a small generator and back feeding the coil till the fan slowed down.
Sandy
Sandy Saunders

OK, problem solved. I installed the GEN warning lamp and the engine now shuts down when the ignition is turned off. Thanks again for all the help. This is a great forum.

Tim
TD12524
TW Burchfield

A brief description on the workings of the ignition warning light. Scroll down a little bit.

http://www.nemgtr.org/53-news/tech-topics/130-the-ignition-warning-light.html

Of note is that several normally good replacement part's suppliers offer new ignition warning lights that are only of any value because they will let you know if your key is on, while the engine is still. They do not have the resistance windings, so that with engine running, they never glow dimly or medium bright, as at low idle for instance. They also use a 12V bulb, instead of the 2.5V bulb, which is correct for the resistance wound units.
D mckellar

D McKellar, Thanks for posting that. My voltage regulator on my '51 has five terminals and the two diagrams I have show nine. I'm trying to figure why my amp meter never moves. I've checked continuity between the "A" terminal and the meter and between the meter and the starter and they check out. Bad meter?
Bob McLeod TD 5618

Bob, should be battery voltage (from starter) at "B" side of Ammeter. "A" side of ammeter should go direct to voltage regulator terminal A. If they are reversed on your ammeter, the needle should still move--backwards.

The RF96 (5 post) is a common replacement for the 9 post. The 5 are A1, A, F, D, E. Any replacement regulator should have the same number (or real close) of windings around the "regulator" bobbin. Less bobbin windings are for a more powerful dynamo. "A1" on the 5 post takes all the A's connections from the 9 post, I think, except of course the "A" wire. These are things like fuel pump, coil, stop lamps, screenwiper, blinkers etc that get current available when the ignition key is turned on.

*** The A post of the regulator should just have the one wire attached, on either 9 or 5 post, and that one wire goes to the ammeter, as above.

Could well be a bad ammeter. If you want a temporary one, it is a pretty standard size instrument and mount, and should be available (often as a trio kit of oil pressure, temp gauge and ammeter) at WalMart or an auto parts store or ebay, etc.
D mckellar

D mckeler, thanks for posting that TSO article. Do you or anyone know where that wiring diagram shown in the article can be obtained?

Tim
TD12524
TW Burchfield

This thread was discussed on 28/10/2016

MG TD TF 1500 index

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