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MG Midget and Sprite Technical - ballast resistor

Can anybody confirm if the pink/white wire in the loom of the 1500 is the ballast resistor wire. I've picked up a sports coil and I'm about to bypass this wire - the trouble is I've just got cold feet and need some reassurance.
Andrew Dunn

Not on my 1500, mine is a piece of fabric insulated wire that is joined at a junction between white ignition wires near the fuse box, and running all the way to a junction at the front grill where it then joins to the white green wire and returns to the coil. ie the ballast is a long piece of wire within the loom.

So the way to bypass it for a non ballasted coil is simply to disconnect the appropriate white green wire at the coil and then run another separate white wire from the ignition switch fed fuse box terminal to your new non ballast coil.

hope this makes sense. I'm sure some more electrically minded members will also help.

regards
steve lowiss
s lowiss

That sounds like a similar wire - the pink/white is definitely connected to the light green/white at the front end and I think it's connected to the white wire at the multiplug in the dashboard - I've moved my fusebox and forgot to update the wiring colours for the ballast wire.
Andrew Dunn

Andrew, if you have a multimeter you could check the resistance of your pink white wire, if it is the ballast wire on later 1500s than my 1975 model, it should have a resistance of about 1.5 ohms ie the difference between a ballast coil which has a low tension resistance of approx 1.5 ohms and a 12v coil which has a low tension resistance of around 3 ohms.

Anyway from what you've just said it sounds like your pink white wire is your ballast wire.
Regards
steve lowiss
s lowiss

You are certain your Sports coil doesn't need a ballast resistor?
Daniel Thirteen-Twelve


If there's any doubt about the coil, use a multimeter set on the ohm scale & take a reading on the coil low tension posts + & -...if it reads 3 ohm, use no ballast, if it reads 1.5 ohm, use a ballast.

I upgraded my ignition to a pertronix system with new distributor & hot coil & pulled a wire from the fuse block to coil +

Runs great, no problems.

Not sure if that was any help or not...

Dave:)
Dave Rhine ('78 1500)

Thanks for replys.
After digesting the wiring diagram further I've now convinced myself that the wire can't be anything other than the ballast resistor wire so hoping to run a new wire from the ignition switch directly to the coil tomorrow. I'll try to do the resistance readings first as confirmation but I know that once I get that soldering iron warm there wil be no stopping me regardless.

Andrew Dunn

Andrew you can run from the ignition switch fed 'fuse box' ie a white feed wire, this is an easy place to take your feed from, as mentioned in my earlier post.
Regards
Steve Lowiss
s lowiss

Also as mentioned earlier, no need for soldering iron just disconnect the ballast resistor wire from the coil, however it should work fine even leaving it connected because electricity likes an easy path and your new feed copper wire will be negligable resistance compared to the original ballast wire.
cheers
steve lowiss
s lowiss

Steve - good idea keeping the existing ballast wire attached - I'm never happy chopping bits of loom out unless absolutely necessary - I may need to revert to std setup if I fry the coil!
There's also some handy free spade connectors at the fuse box and coil ready to accept the new wire. Looks like it may be any easy job - Where have I heard that before?
Andrew Dunn

I've kept all of my unused wires & connectors...just in case!

I put them in a loom to tidy up the appearance.


Dave Rhine ('78 1500)

This thread was discussed between 22/04/2010 and 25/04/2010

MG Midget and Sprite Technical index

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