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MG TD TF 1500 - Coil Wiring

Hi All
I've looked in the archives but can't find anything
Does the wire from the distributor go to The negative or positive side of the coil?? My coil is not marked SW or CB
Regards J
J A Davies

Pretty sure this depends on how your car is earthed, either + or -. Apparently the coil is slightly less efficient if wired in reverse. Polarity is critical however if you have a pertronix or 123 electronic ignition fitted. Cheers
Peter TD 5801
P Hehir

The + terminal on the coil goes to the positive side of the car i.e. on a positive car + terminal goes to the points and the - terminal goes to the ignition. On a car with a good ignition system, it really doesn't matter which way the coil is installed, but in a car with a flakey ignition, the way the coil is wired could be the difference between the ignition working and not.

The ignition coil is actually an auto transformer, where the primary and secondary coils are in series with each other so the direction of the current flow in the primary can be wired such that the current flow through both of the coils can be additive or the primary can subtract from the final output. This produces a small difference with the output of the secondary coil.
DW DuBois


In a neg ground car the (neg) - terminal of coil goes to distributor.

In a pos ground car the (pos) + terminal of coil goes
to distributor.

D mckellar

Many thanks for the help all sorted now
J A Davies

This thread was discussed between 10/04/2017 and 12/04/2017

MG TD TF 1500 index

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