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MG TD TF 1500 - Ground Design

I have always been intrigued by the ground design throughout the TD. It's as though the engineer that designed it quit half way through and some else finished it. The tail lights all have a dedicated ground to the frame whereas the front are dependent on a metal to metal contact at the fender mount. The engine is nicely grounded by a dedicated large strap to the frame yet the firewall is dependent on metal to metal contact. I can see where a problem could exist when in restoration one does an outstanding paint job inhibiting the metal to metal ground. I will definitely be cleaning paint off certain mounts and performing continuity checks between panels.
Mike Hart (52 TD 16378)

You are sure right about ground problems. Read David DuBois's article on how to prepare painted holes, conductive coatings, etc. George
George Butz

An odd thing, Mike --- it's actually the firewall that gets the primary ground connection via the battery cable. The engine ground depends upon how well the frame is electrically connected to the firewall. I seem to recall that Dave DuBois has some good suggestions on grounding. (Or, is it another Dave?) Bud
Bud Krueger

See the article, Electrical Connection Preparation in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ for information on how to insure a good, long lasting ground connection. I have been a long time advocate of running dedicated ground wires into the headlight buckets instead of depending on 4 different junctions of various components to carry the return current back to the battery. I hadn't given the firewall any thought as Bud mentions, but it would be a good idea to add a ground cable between the firewall (prepared as in my article) to the same cable connection as the engine ground. The less ground paths that depend on the structural connections to double as electrical connections, the less number of potential problem points there will be. Cheers - Dave
David DuBois

I fully agree with you Dave. It seems odd they would provide a dedicated ground to the rear light and not front. I plan to install the same type ground between the firewall and frame as the engine and frame.
Mike
Mike Hart (52 TD 16378)

Speaking of grounds....my right front headlight when turned on is very dim...I tap the bucket (sometimes with great vigor) and it pops back to bright....I have removed it a dozen times and tried to find a bad connection (bulb to holder...holder to frame...etc etc) and no matter what I do it remains dim till I hit it..... any hints....?
gblawson(gordon- TD27667)

Gordon - This is he very thing I addressed above. The ground for each headlight is a push connector inside the bucket. the ground path then is the headlight bucket to the mounting bracket, from the bracket to the fender, from the fender to the frame of the car. To take this even further in light of the battery being grounded to the fire wall, we now have the headlight ground going from the frame to the firewall via the right and left towers and then to the battery. The only two connections in this whole chain that have anywhere near a good connection (no paint or corrosion between the two surfaces) are the push connector in the head light bucket and the battery ground cable to the firewall. Kind of make one wonder how the headlights shine any brighter than a flashlight with 2 year old batteries. In your situation, it sounds like the push connector in the headlight bucket is probably in need of some attention. Cheers - Dave
David DuBois

Thanks Dave...will pull it apart again...I have sanded and scraped every piece of metal that makes contact with another....but.... will do it again. Haven't done anything outside the casing, but thought because it worked when I banged it that it had to be inside?
gblawson(gordon- TD27667)

Gordon - It could be where the swivel mounts in the bracket. The ultimate fix is to run a ground wire from a convenient point on the frame of the car up into the headlight bucket and attach it directly to the ground wire for the light socket - a big job, but would eliminate any ground problems for the headlights. Cheers - Dave
David DuBois

This thread was discussed between 06/11/2010 and 07/11/2010

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