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MG TD TF 1500 - TF 1500 coil overheats

Coil on my 1955 mgtf 1500 overheats badley. I replaced it and the problem still exists. Could this be related to the voltage requlator?
bill angevine

How much is badly? I don't know if mine runs warm/hot/cold or not...never thought to touch it?
gordon lawson - TD 27667

Bill,
Could also be related to wires! When I was running "the popular re-placement wires" I had same problem. Switched to Lucas "Bumble-Bee" cable and coil is much cooler now. (Lucas Sports Coil)
Cheers,
David 55 TF1500 #7427
David Sheward

Gordon - thanks for the fast response, Hot means too hot to touch - damp finger sizzles.

David - the wires have not been changed since restoration in 1999. I have checked all connection and the wires themselves and they all look OK so I ruled wires/connections out.

Need some help on the voltage regulator, as that may be the problem
bill angevine

Bill,
You can have "good continunlty" but still too much "resistance". Same princple as running a hi-amp power tool through a "cheap" extension cord! The cord & the breaker will heat up before the breaker pops! The "DYI" wire kit sold for these cars is crap wire. I went through 3 of them in a season and 2 coils that "looked" like low spark output and overheating problems. I had also fitted a spare VR to the car. (MY TF "came" with "spare" VR, coil, dizzy & wires) All of those had been on the car at sometime! Once I changed the wires to better quality I aquired some "good spares". In hide-site this should have been a big red flag to me. Since changing the wires I have had to install a cig-lighter as I can no longer get a lite off the coil! LOL
Cheers,
David 55 TF1500 #7427
David Sheward

bill A -- I can't offer any comments on the coil being hot. But I can give you some insite into the VR. First the voltage tests outlined in the shopmanual are pretty comprehensive. But if you study the proceedure I think you will discover that the battery is disconnected during the voltage output adjustment procedure. I find that when the battery is disconnected the voltage goes up about 1 volt. So maybe the voltages in the shopmanual are not as high as I originally thought. What I like to see is the ammeter go up pretty good right after a start then start to come down. When it gets down to a few amps, then I like to see 14.2-14.3 volts across the battery. To see if the vr is regulating turn on the sidelights (parking) lights. The voltage and the ammeter should remain the same. As the regulator picks up the load of the lights.

The coils will run warm but so hot as to sizzle when touched with a wet finger is a bit much. The original coil for the TF was a Lucas LA-12.
Primary Inductance 11.0 mHY
Primary Resistance 3.3 ohms
Secondary Inductance 55.3 Hy
Secondary Resistance 8,250 ohms

The usual Sports Coil was an SA-12.
Primary Inductance 10.39 mHY
Primary Resistance 2.6 ohms
Secondary Inductance 76.3 HY
Secondary Resistance 10,050 ohms

I hope some of this helps.
Cheers,
Bob
R. K. (Bob) Jeffers

Bill - Check the gap or dwell for your points. If the gap closes up (and it does as the rubbing block wears), the dwell or time that the points are closed and current is flowing through the coil increases, making the coil run hotter. The more the points close up, the hotter the coil will get. Also Bob Jeffers above, is too ethical to advertize on this board, but I can tell you that he makes a solid state replacement regulator that will fit in yur original housing if your regulator does turn out to be bad. Bob turns out a really nice looking, well designed product and then polishes the housing he puts it in so that it looks better than new. Cheers - Dave
David DuBois

David DuBois makes a good "point" (pun intended here)!
I kind of skipped right over that as I still had overheating in mine even after changing to a pertronix unit.
Cheers,
David 55 TF1500 #7427
David Sheward

Bill,

I think your problem is with the coil itself. This may sound a bit strange, but the coil you are attempting to use either has a built-in "ballast" and the MG system doesn't require it OR the coil does NOT have a built-in ballast and the MG system does require it. I know from experience that this ballast issue causes the exact result you describe. Eventually the coil will literally burst open.

Reed Yates
'54 TF
Reed Yates

I also found that as my points wore, the car became so hard to start that I re-set them before they had a chance to heat up the coil by much? Not sure where it came from, but my coil has a giant heat sink (Lucas Sport Coil #?)
gordon lawson - TD 27667

Gordon,
You sure that isn't a Ballast Resistor? Our LBC's need a 3 ohm coil. ( These ballast look like a big heat sink) By the way you are allways best off to check this with a meter. I had 3 coils I purchased for our Opel GT that were marked incorrectly from the maker!
Same is true of + and - markings on speakers. I used to get them all the time marked wrong and would end up installed out-of-phase.....cheap trick for those, 9 volt battery across the terminals ..cone moves "out" for "in-phase" / "in" for "out of phase!
Cheers,
David 55 TF 1500 #7427
David Sheward

Grabbed a photo-
Coil: http://gblandco.com/gb/2006spring/coil.jpg
Oil Gauge connection: same photo
Sidecurtain rivets: http://gblandco.com/gb/2006spring/curtain1.jpg
Sidecurtain rivets: http://gblandco.com/gb/2006spring/curtain2.jpg

I thought the coil was just a 'finned' cover, but when I removed it to paint, all the threads were 'peaned' over. I was then told that that is the whole coil rather then a cover! Still have to sand/polish the fins.
gordon lawson - TD 27667

Gordon....never seen that one before!
David Sheward

Thank you all for your help and advice! The regulator problem, causeing the coil to over heat, was corrected by cleaning the points, regaping them and adjusting cut in and cut out times with a meter. We found the old fashioned style with a gauge was more stable and useful. The main issues are patience and luck!
Thanks again - bill
bill angevine

Not the selfsame Bill Angevine who works for the same company I do, is it? Didn't know you have a TF.

Cheers,
Lew Palmer

Lew Palmer

This thread was discussed between 14/07/2006 and 17/07/2006

MG TD TF 1500 index

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