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MG TD TF 1500 - TF horn and parking lamp connections

The left TF parking lamp is very bright (compared to the right lamp) and generates a lot of heat when switched on during testing. Only one filament is burning (and at 13.5 volts).
1. Does it matter how the bulb holder is wired (red or green)?
2. How about the horns (brown/Gr and brown/Blk)?
3. For a negative ground TF, does the red distributer wire connect to the + or - on the coil? (tough to get a direct answer to this one).

thanks for help. Lots of electrical bits to sort out.

Tyler Irwin

Easy to correct on number 1... remove the bulb and turn it 180 degrees and put it back in. The locating pins are not offset like an 1157 bulb so you have a 50 50 chance of putting it in wrong.

1. No
2. I'd have to get out the diagram but yes the brown leads feed the horns. Should be a pair emerging from loom for each horn.
3. The wire from the distributor should be placed on the negative terminal of the coil for you application. The white wire from the harness should go to the positive terminal of the coil. I don't know where you are getting a red wire from?? Maybe part of the confusion from the group.
L E D LaVerne

Taylor, I usually stay away from TF things, but I think I'm safe on this one. Looking at the TF wiring diagram (WSM N.29) I see that the red wire (41) for the sidelamps goes to the sidelamp circuit and the green/red (18) goes to the turn signals. The turn signal filament is a higher wattage than the sidelamps. You want to swap the wiring for your left lamp.
Horns don't care which wire is connected to which terminal.

Think of the +/- markings on the coil as pointing toward that polarity in your system. If you are set up for negative ground the + terminal wants to be on the +12 volt side and the - terminal wants to be on the negative side, i.e., to the distributor, hence to ground through the points.

I would expect the distributor to have a white wire (9) and a white/black wire (16). Red wires are generally only in lighting circuits, white are 'hot' with the ignition switch. The OEM coil seems to be labelled as 'SW' (switch) and 'CB' (breaker points). The 'SW' is the same as '-' and 'CB' as '+'.

Bud Krueger

I assume the TF has dual filament bulbs.
There is a normal filament and a bright filament.
The normal should be wired for the running lights and the bright one for the directional blinking.

There are two kinds dual filament of bulbs. One has a single bayonet nib, the other has dual nibs at different spacing from the socket end.

If your lamp bases are set for the dual nib and you have a single nib bulb, it is possible to insert the bulb in a reversed fashion.

For TF, WSM shows brown with black from horns to horn button to ground.

Brown with green to A2 fuse.

Jim B.
JA Benjamin

Folks the TF bulbs are two lug but they are not offset (yes they are odd) and it's a lot easier to just flip the bulb 180 degrees than to pull the assembly out and swap the wires.
L E D LaVerne

Forgot about those oddball bulbs and sockets.
Jim, I think that Tyler's concern was with the wires as connected to the horns. It shouldn't matter which side of the horn gets the brown/green (38) and the other side gets the brown/black (40) wire. Bud
Bud Krueger

This is very useful info. Now, I can keep moving on checking the connections. Getting close to starting it up with everything connected.

Tyler Irwin

Don't forget the horn is permantly live and the ground is via the switch. This is a throw back to the days when the horn button was in the centre of the steering wheel. It was safer for the ground wire to pass up the tube in the column than a live one.

Jan T
J Targosz

This thread was discussed between 30/12/2016 and 31/12/2016

MG TD TF 1500 index

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