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MG TD TF 1500 - Converting to Negative ground Early TD

Sorry everyone as I know this has been talked about before. I tried the archive search and quite frankly find it useless most of the time as nothing ever comes up when I do a search. That being said...What is the correct procedure when it comes to converting the wiring etc to go to a negative ground system. I have a new upgrade turn signal full harness system in the car but it uses my original regulator with the built in fuses Car # TD4834. I want to have everything in place so when I finally get my engine in the car I can insure that all the Lucas smoke stays in the harness.


Bill Chasser jr
W. A. Chasser Jr

There is no need to convert to negative ground.
It is useful when using modern electrical equipment or an alternator.
Jim B.
JA Benjamin

Bill - See the article, Polarity Change in the other Tech Articles section of my Homepage at: Cheers - Dave
D W DuBois

Here's a test run through the archives for you...

1 go up and click "Archive"

2 enter "negatvie ground conversion"

3 click "all of these words" this is important to eliminate unrelated posts

4 click "START SEARCH"

Jim, I have the need to switch over or I wouldn't be asking. Thanks for your input.

Dave, thank you. I knew the information was out there some where. I was on your site before I posted this but missed it I have new transistor blue tape pumps

Jim, I do that but I'm always getting no hits. I've even done it to my own threads and they don't come up

Thanks everyone

Bill Chasser jr
W. A. Chasser Jr

Bill, Jim's search above returns a whole screen full of hits but you must spell the word "negative" correctly (sorry Jim). You can search for "this phrase" or "all these words" and get many hits. Maybe you're using the "Search" feature instead of the "Archive" feature above? The former doesn't work. The latter works fine.
efh Haskell

Bill read Daves article. If you have LED lights you may need to change their polarity and if you have an electronic fuel pump wired for positive ground you will need to change that too. But it is really pretty straightforward. If you need more email me I think I assembled more info on the subject before I did mine and probably have it somewhere...
Geoffrey M Baker

Thanks Geoffrey. Yes I went to search not archive. I thought the search would automatically access all sources. Go figure? Any way What I have done is installed two new negative ground SU electronic pumps on the firewall, Negative ground LEDs will be installed in the tail lights, I have an O2 sensor going into my header, iT may get an electric fan down the road for cooling if I have an issue as well In reading Dave's tech sheet on his site, there are no wires to change on the regulator. It is only the ammeter wires that need to be switched and remove both wires from the dynamo and jump a wire to the starter wire to excite the charging system. Seems pretty straight forward.

On a side note is there a LED to install in the wing marker lights that also carry a turn signal circuit? Moss doesn't show one
W. A. Chasser Jr

It is pretty simple. I had to redo my rear LED lights to neg ground and rewire Dave's optoelectronic pump, but other than that it was extremely simple (although I really was nervous changing it over!)
Good luck - and it's a good idea - anyone using modern electronics (sound system, security, gps etc) should convert over plus it saves the danger of a helpful individual with jumper cables or a well meaning but ignorant mechanic blowing it for you! One piece of advice - I added a large laminated sticker to the toolbox warning that this car had been changed to negative ground....
As far as LEDs on the front, I haven't got around to building my own high power bulbs yet (but plan on it). There should be suitable bulbs available at, but they may not be as bright as you want.
Geoffrey M Baker

Re: LED's in the front turn signals - I did a small retrofit (very easy) and installed two bulbs in the front unit - one white as original and the other yellow for the turn signal. I then tried to convert to LED bulbs and just cannot find any that give out as much light, so for the time being I've left them as is.
Chris Malcolm (TD29228)

It's been about five years since I built my own high power LEDs for the taillights . I still haven't found a "drop-in" LED bulb that is anywhere near as bright. But soon, I think... there will be more powerful drop in bulbs. I did built a prototype front one, but I couldn't get it to work with a positive ground flasher (they didn't at the time make LED-ready positive ground flashers, the existing positive ground flashers din't work as they need more current draw to operate). I have converted to negative ground since, and a no-load LED compatible flasher should work just fine, but I just haven't got around to converting the front bulbs yet.
It's amazing how engine failure can get in the way of your other projects :)
Geoffrey M Baker

This thread was discussed between 13/04/2015 and 14/04/2015

MG TD TF 1500 index

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