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MG Midget and Sprite General - Why is both my dissy and my coil super hot

Okay here is a strange one

Both my coil and my dissy are super hot...in fact I got a nice crispy burn on my finger tip from touching the metal body of the dissy.

After about 30 minutes of a nice spirited run I broke (ANOTHER) bicycle cable, so while messing with it at the shop in near dark, the engine shut down like the key was turned off, so feeling around for loose wires I burnt my fingwr on the dissy and felt the coil was super hot, but the wireing was all cool...

I havent tested for spark or investigated further,,,,but im 99 % sure its electrical...there where no issues before hand, vary smooth, no stuttering, missing, ect...vary nice and even

Soooooo....what would cause both the dissy and the coil to be super hot after 30 minutes, but leave the ALL the wires cool or are the dissy / coil heat issue unrelated

1971 1275 USA spec. pretronix chip, stock dissy, standard coil..no ballast resistor....all wires are in new shape, and have solid connections,,,,(from what could see and feel)

Prop
Prop

Surely it has something to do with the power being sucked to your gauge/iphone installation, it has to be! LOL!!

Reminds me of Chevie Chase in National Lampoon christmas movie when puts power on his christmaslight installation on the house. :)
Arie de Best

Are you saying the distributor was hotter than the engine block? It may have felt hotter since it is aluminum and transfer energy faster than the iron block.
Trevor Jessie

Prop,

Sounds like a grounding issue. Try running a heavy duty ground wire from the coil mount to the negative ground on your battery.

L.C.
Larry C '69 Midget

Exactly treavor....i know it should be warm, but this was brutle

Grounding issue is all I can think of as well....ive just never seen both being an issue, but id thought the wiring would have at least shown signs of heat there fine, almost to cool.....

headed to the shop in a few minutes to see whats up before work

Prop
Prop

I kind of wonder if I got 2 seperate issues and the dissy is rejecting its bearing

Ive got a gut feel that the heat toasted, the P. Chip

Prop
Prop

Prop, always start with the simplest explanation for a problem first before charging out for more complicated causes. Common cause for a hot coil, too much voltage! That's it. Most often caused when the proper dropping resistor is not installed when converting to an electronic ignition system. Some use resistors, some don't. You need to find out which type you have.
Second cause is power to coil all the time, should be switched off when the ignition switch is off. Check your wiring.
Either cause would heat up the coil and also the ignition module in the distributor due to excessive current.
What are the bicycle cables you're talking about? If you've broken two of them in such a short time you need to find something more reliable, they shouldn't break that often.
B Young

What was it then? Sounds interesting.

If the coil and the dis were both hot, (excessively) then it's obviously electrical and not mechanical, unless by coincidence you do indeed have two seperate issues. One mecahnical like a bearing, and one electrical, like a poor connection.

I'd go for HT related. The LT wires would burn out long before the coil and dissy both got hot enough to burn your fingers, unless you wired the lt in heavy duty cable of course. :)

But you said this was cool, so it spoints to HT.
Was the coil to dis HT lead hot too?

Eliminate the electronics, and put the points back in for a test if you still haven't sussed it.

And how about that bike cable, this may be related if it shorted something.

Lawrence Slater

This thread was discussed between 13/07/2011 and 16/07/2011

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