British-Cars.org

Welcome to the DMR Site for British 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 - Alternator conversion/ignition warning light

Conversion of my '53 TD to a '78-'80 MGB style alternator went well except for an odd ignition warning light problem. Turning the ignition key on for the initial start-up turned the warning light on and showed a slight discharge on the ammeter. Starting the engine made the light go out and a proper charge indication on the ammeter. Turned the key off and the light came on. Turned the key back on and the light went out. The engine would continue to start OK; the light would come on during ignition and would go out when the engine started. Turn the key off and the light would come on. If I disconnect the battery cable (with an accompanying "thunk" from the regulator) and then reconnect, the start-up process will go correctly as on the initial start-up after the conversion. Turn the key off and the malfunction happens again. I went through the same series of events several times and decided that I should ask for comments from this site. Any suggestions would certainly be appreciated!

Regards,

Bobby Loughridge
B. F. Loughridge

Bobby - I assume that you also converted to positive ground when you installed the alternator. You mention that the regulator goes 'thunk' when you disconnect the battery, which prompts me to ask if you are still using the original TD regulator? If so, then that is your problem. Depending on the MGB alternator you got, it may have a remote regulator that is specific to the alternator or it will have a built in regulator, in which case, you shouldn't be using a remote regulator. Cheers - Dave
David DuBois

Bobby. This is as it should be.
An alternator is chrging the battery from the
first turn and the light goes out showing that the battery is being charged ok. While
a generator needs more speed to charge the battery. I believe. Somebody corect me if I
am wrong.

regards Thoralf TD 4490
Thoralf Sorensen (TD4490)

Bobby/Dave -
That would be "converted to negative ground" as virtually all alternators including this one are negative ground.
And this alternator certainly does have an internal regulator, as most modern ones do.
So, you have managed to wire it such that you have the OE regulator pulling in and not releasing. Review the wiring instructions you used in the conversion - it varies by which method you use and can be problematic if you use the OE reg as a connection point. This problem has been recently discussed on one of these boards, probably the MGA one.

FRM
FR Millmore

Dave and FRM; Yes, I converted from positive to negative ground in the process. Actually, I used Moss Motors instructions for installing the MGB alternator in an MGA, since the MGA uses the same regulator as a TD. Of course, that may explain why Moss sells a conversion kit for the MGA and not the TD. The directions are fairly straightforward; move the yellow wire from the 'D' terminal to the 'A' terminal and attach the yellow wire at the alternator to one of two large connectors. Move the yellow/green wire from 'F' terminal to the 'D' terminal and attach it at the alternator at the small connector. The yellow ignition warning-light wire apparently stays connected to the 'D' terminal. Depending on what I learn here, I am considering disconnecting the yellow ignition warning-light wire from the 'D' terminal or else try moving it with the main yellow (battery) wire to the 'A' terminal.
FRM; I was reasonably certain that the MGB alternator was externally regulated, since that is what Moss sells in their generator conversion kits for both the MGA and early MGB and provide directions for wiring via the existing regulators. I should also mention that Moss has a strong admonition about the need for cleaning and adjusting contacts for regulators that it sells and has a very good write-up on the matter. They also sell one that is precleaned and adjusted.

Thanks and regards,

Bobby L.
B. F. Loughridge

Thanks, FRM. I went to the MGA archives and found the same problem described in about 2006. Reference was made to MGAguru.com page AC101. The guru discussed exactly what I had experienced (including following the same directions that I had used with the same result) and described a simpler way to do it. I'm still using the old regulator for a connector box, but will be substituting heavier wire, possibly going directly to the battery/starter post. I disconnected both the yellow green wire and the yellow ignition warning-light wire from terminal 'D' and simply connected the two wires. As far as I can tell right now, the system is working as it is supposed to. Thanks again for pointing me in the right direction!

Regards,

Bobby L.
B. F. Loughridge

Bobby -
Yes, the use of the old reg as a connection point can lead to odd things. I haven't done it and am not likely to, preferring to keep things functionally straightforward at the expense of "ease of conversion". There was more discussion that involved people putting insulating material between regulator contacts for a similar problem.

FRM
FR Millmore

This thread was discussed between 21/08/2010 and 22/08/2010

MG TD TF 1500 index

This thread is from the archives. Join this live forum now