Welcome to our resource for MG Car Information.



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 - Upside down, sparks, then cursing, now silence

I was upside down trying to tighten my new starter cable under the dash when my wrench arc'd on something. After my initial reaction (guess), I checked everything out and it all seemed fine.

Howeever, once on the road I noticed my horns do not work. I checked fuses and they're both fine. No wiring was upset, and the shop manual indicates the fuses and wiring are about the only way to lose connection for the horns. The headlights continue to work as well.

Any ideas what to test next?
Stan Griffis


The horns are actually hot all of the time, the horn button grounds the horns to complete the circuit. Do you still have panel lights? You might want to check and see if you've lost the ground at the red side of the inspection socket. (assuming your car is positive ground.) The panel ground is from a black wire that runs to terminal E on the voltage regulator. ( you could also check continuity between the panel and terminal E.)

If you have turn signals, the indicator light also uses the same ground.

Let us know...

Evan Ford - TD 27621

From memory I know I've got panel lights. I can check the inspection light later today.
Stan Griffis

Did you test the fuses with a meter or light or just look? A fuse can blow and look ok, same with corroded fuse block terminals, etc. You should have 12v at the horn on one terminal, as Evan said the button completes the ground.
George Butz

You might also want to make sure the fuse is making good contact with the fuse holder. The horn fuse is between terminals A1&A2. Note: this is a 50 amp fuse! -the horn wires will get plenty hot before this fuse blows.
Evan Ford - TD 27621

I used my ohm meter to check continuity of A1 and A2's fuses, and they both checked out.

Is the horn fuse independant of the A1 or A2 fuses? I thought there were only 2 fuses in the whole car. Between A1 and A2?

Stan Griffis

Remove the horn cover, and check for voltage at the terminals (one end of your meter to ground). If you have 12v, figure out (remove one) which terminal is the hot side. With the hot one connected, ground the other one and the horn should blow. If that is the case, then it is a ground to the dash panel/horn switch problem. If no juice, trace back to the fuse box. My manuals/diagrams are at home now so I cant' look up which fuse does what. George
George Butz


I just emailed you a simplified wiring diagram.

As for the fuses, the horn fuse connects terminals A1&A2 and the other accessory fuse connects A3&A4. It fuses the wiper motor, brake lights, low fuel light and turn signals.

Evan Ford - TD 27621

Well, since both fuses passed the continuity check, I'm guessing it's the ground issue you mentioned. Tonight I'll check the ground of the inspection light port. I don't have signals, so checking there isn't an option.
Stan Griffis

Okay, so I went out to the car and redid the continuity check on each of the fuses (outside of the holders) and they both tested good. I put them in the block and they tested as they should, except that A1 and A4 when I checked across them (don't ask why, I was checking everything) had continuity.

This confused me.

So, I removed everything again, and nothing passed a continuity check (A1, A2, A3, A4 I mean) so I figured that was good. I reinserted the fuses, and now everything (Horn etc...) works perfectly.

Lord Lucas is chuckling as I type.
Stan Griffis

HeHe Exactly why I never throw out electrical parts for the TD. Have found more than once that sitting on a shelf can somehow miraculously make them work again.
Bruce Cunha

This thread was discussed between 12/08/2004 and 13/08/2004

MG TD TF 1500 index

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