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MG TD TF 1500 - DOH! I might have become dislexic in my old age!

Got the front "wings" mounted on Sunday....First senior moment was noticing that the hold-down brackets were on backwards!
But , fortunately , I had not bolted down the wings, so aggravating, but not a disaster....
Then it was time to wire the headlamps to the new harness....I was so proud of the wiring job, using my new (and expensive), bullet crimper....(love it , by the way).
Then the moment to test the headlights....Double bright on main, nothing on "dip"...(I'm the dip, I think)....
Got out the wiring diagram...HELLO!...Used double wiring connector on each lamp, so high and low beam were on at the same time....No problem, right?
Well I separated the wires, and could only get high beam...DOH!...Didn't flip the "dip" switch!
Sorry....Had to post this just to laugh at myself.
Seems "Rocky" has the right name!
E.B. Wesson

Edward - Using the information in Rick Astley's book, I added relays to the headlight circuit on both our TD and MGB. In the instructions, Rick gives the option of having both the high beam and low beam filaments active when high beam is selected (just low beam filament active when low beam is selected). I also added a couple of relays to provide daytime running lights to both cars. Cheers - Dave

PS. Those bullet crimpers are the only way to go!
Daved DuBois

Yes , I'm familiar with that circuit...In fact, I have been using it in my Cobra replica for many years...
I haven't really considered it for "Rocky" , since I still have the old-style sealed beam headlamps...They seem to be really bright...
If I have to go to halogens, then I will have no choice, but to use relays.
Thanks for the suggestion.
E.B. Wesson

Having both high and low beams ON at the same time will pull approx 20A - more than a Lucas generator can supply. And, it will cause the lamps to overheat - IF you have full voltage at the lamps - which you won't, especially if you don't fit relays. Also likely to melt the earth connector and wire, which are usually not good to start with, and which carry full current load of both filaments - I recently found both earth contacts/connectors on my newly acquired Mazda van headlamps near molten - and poor light output.

I get HD ceramic connectors from Daniel Stern or Susquehanna Motorsports.

Having measured many cars, of all sorts and conditions, anything but a brand new wiring system will typically show at least a one volt drop between the battery and the lamp, and two or more volts is typical - if you are anywhere close to the 13.5V you should have at the lamp, one volt = 30% of your light output. I find most cars delivering between 9.5 to 11.5V at the bulb if the wiring has not recently been redone, and only relays will give full voltage. At 9.5, you need a flashlight to find the lit headlamp - it is putting out about 20% of rated output. I get all my systems to less than 0.5V drop as measured across the bulb contacts vs gen/alt output.

Further, eliminating the heavy load from the headlamps reduces the loss in the rest of the system, and your tail/brake/TS/wipers/heater will all be much happier - a SERIOUS SAFETY issue, especially on early cars with insignificant taillamps.

FR Millmore

This thread was discussed between 26/09/2012 and 28/09/2012

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