XJ12L hot coil

[nigel0658717]

Good afternoon,

It's me again. The next item on my list is the very hot running. The additional Kenlowe fan is permanently on, but it's still hot. Water levels in both radiator and overflow tanks is mine.

On a run in the heat thus week, the coil was so hot that it was impossible to get anywhere near it.

A Lumenition replacement system was recommended, but, given that they're not cheap, I am hesitant to purchase unless I am confident that this will be worthwhile.

Any thoughts will be gratefully received.

Thanks

[PaulGover]

Nigel, can you give us some more details of your car - age etc.? The V12 ignition system has had several variants over the years, as indeed have most of the engine gubbins. If you're not too sure, a close photo of the engine bay might help.

On overheating:
AFAIR the electric fan will stay on if you have air-con switched on, as the car assumes the extra load will need it.
What does the temperature gauge say?

[nigel0658717]

Hi Paul,

It’s a 1973 series 1, registered June 73, so towards the end of S1 production. No air con.

A pal today has gone through the wiring with the help of Haynes manual, and carried out their suggested checks. The conclusion so far is that the ballast resistor is really hot too, pulling 9v instead of 2v on start up.

Holden offer a replacement kit, but, also, not cheap, and I’d like to be certain it will solve the problem.

[PaulGover]

Ah, too early for me to be able to offer any insights. I can tell you lots about the Marelli electronic ignition in my Facelist, almost 20 years younger...

[poprivet]

There are a couple of E Type V12 forums which may be of help and may reach more owners then here.

Is it the engine heating the coil or just a very hot coil?

[PaulGover]

... A pal today has gone through the wiring with the help of Haynes manual, and carried out their suggested checks. The conclusion so far is that the ballast resistor is really hot too, pulling 9v instead of 2v on start up. ...

If the resistor is dropping 9V, then the coil is only dropping 3.5V, which is about the inverse of normal. It would mean a current of around 9A rather then the usual 2A or thereabouts, so I'd suggest your coil is seriously defective. Replacing that should be pretty cheap to try.

That's assuming I understand what you mean by "pulling 9v instead of 2v on start up". It's normal for the ballast resistor to be shorted out at start-up (and therfor should drop 0V) to provide ample volts to the coil while the starter motor spins (taking ~500A, and dropping the battery voltage to around 9V). As soon as the engine fires and the starter stops, the ballast resistor comes back into circuit so the coil sees a roughly constant 9-10V feed.

edit to add:
AFAIR, the early cars should have two coils - one with nothing connected to the high tension side, but the normal connections on the low tension side. That's so you get twice the magnetic field built up before the points (or electronic equivalent) open. Then you get two fields collapsing at once, to provide a fatter spark - or as the V12 fires twice as often as a 6-cylinder car, about the same spark as you'd normally see.

[nigel0658717]

Hi Paul,

Thanks for your informative reply. The car definitely has one coil and a balance resistor, so this may be a modification. The Haynes manual also says 2 coils, although on the next page discusses how to test the balance resistor.

Going through the Haynes checks all electrical readings readings are exactly as they recommend with the exception of the balance resistor which was reading 9v instead of the recommended 2-3v.

The fault diagnosis section suggests the amplifier may be the problem, so I'm not any clearer, whether coil, amplifier and/or balance resistor is the problem area.

I'm picking the collective brains because I don't want to shell out only to find there is a less expensive solution, or that the replacement sytems don't resolve the problem.

Thanks again.

[mike020150]

I suspect you need to go back to square one with this query to establish precisely which ignition components you have on the car. One coil is not a problem as long as it's the correct Lucas low voltage coil for this application. Similarly, there are multiple versions of the ballast resistor pack (all basically looking the same), so you need the correct one. Coils and amplifier units are matched. Again, an incorrect combination will cause problems. If you list all of the stamped markings and labels on the amplifier, the coil and ballast resistor, it may be possible to see if your car has the correct combination of these units. Mike.

[nigel0658717]

Thanks Mike.

[nigel0658717]

Thanks to those who contributed their thoughts to my original query.

I feel that the conclusion is that I need to replace the entire system and there are 2 likely candidates, both costing around £650.

Is the collective thought that I should go for a Lumenition system or the Opus replacement from SNG Barrett/Holden? The SNG Barrett bundle comprises Coil, Balance resistor, Amplifier (which Haynes manual says is the most likely failure) and distributor.

Thanks

[mike020150]

FWIW if you decide to replace the complete system, the SNGB replacement system has been around a long time and has proved reliable in service. Mike.