Coil Overheats alfasud 5m

[Jerran]

Hello, Can anyone shed any light? The ignition coil on my 5M seems to get far too hot, after half an hour of tick over the car will cut out, the coil is almost unbearable to hold, at the same time the spark at the plugs is almost non existent. Is this just an over age coil are are there ignition issues elsewhere?

[alfadave]

Had an overheating coil once before,on a ford crossflow.
I had inadvertantly fitted a coil to suit a ballast resisted system on a non ballast resisted car.
Try another coil?

[Spacenut]

I was going to say the same thing - a coil for a ballasted ignition system runs at about 9V due to the volts drop across the ballast resistor. Operating the starter motor bypasses the resistor, putting the full 12V across the coil to get an extra boost to the spark on starting. Once the engine is running, the resistor is put back in circuit and the coil runs on 9V again.

The Alfasud does not have a ballast resistor so a ballasted coil will be running with 12V all the time, which will lead to overheating and eventual failure.

If the engine is cutting out I suspect that the coil is breaking down internally - high voltage is arcing through the insulation (oil) between the HV and LV coils, effectively by-passing the spark plugs. The arcing leaves a trail of carbonised oil particles that can act as stress raisers for further internal arcing.

Even if it is not a ballasted coil, it is clearly of the wrong specification for your ignition system. I believe there were two types of coil resistance used on Alfasuds over the years. You probably need the other one

Not all ignition coils are the same!

Lauren

[Jerran]

I've just ordered an Accuspark high performance ignition coil, no mention in the listing if it had a ballast resistor or not, have I ordered the correct one for my Sud ? Do I need one with a ballast resistor or without ?

[alfadave]

The ballast resistor is a seperate item
you can see one on accusparks website, item BL1

Alfasuds never had ballast resistors

So hopfully you have ordered ACU 105 sports coil,
or ACU 101 standard coil

both ok for non ballasted systems

Dave

[dave.armstrong]

Have you checked that the coil is earthing Ok through the bracket.

[sudboy1490]

I'm having the same problem on a ducellier electronic coil I have. Does anyone know if an Electronic system coil is any different to a point based one. Theres loads advertised on ebay but no mention if they're for electronic or points??

[alfadave]

I thought the only electronic ignition systems on suds were Bosch or Marelli.
I found the Marelli system unreliable......the wire in the dissy flexed as the vac advance operated the moving plate, and the wire bared after a time causing mis fires.

The Bosch system is ,I think more reliable, and parts easily available.....it was used on 83-89 33's.
And some Fords had the same cap/rotor.

I would buy a Bosch dissy/coil unit from Justsuds.....a fairly easy swap.

Dave

[Jerran]

Ok, so my new accuspark coil ( non ballast ) still over heats. In answer to one question, it's not bolted to the body of the car currently, will this affect it ? I'll be getting the car out again tomorrow to test, I'll bolt it to the body by the brake reservoir where it should live. I've replaced the condensor in hope this will help ? Any other thoughts/suggestions welcome as I want to be out there enjoying my 'Sud !

[Spacenut]

Ok, so my new accuspark coil ( non ballast ) still over heats. In answer to one question, it's not bolted to the body of the car currently, will this affect it ? I'll be getting the car out again tomorrow to test, I'll bolt it to the body by the brake reservoir where it should live. I've replaced the condensor in hope this will help ? Any other thoughts/suggestions welcome as I want to be out there enjoying my 'Sud !

Bolting the coil to the chassis shouldn't make any difference, as there is no electrical connection between the can and the transformer windings. The condenser helps to reduce the flash-over when the points open, which again should not affect the coil overheating. The only thing that will cause the coil to get hot is if it is sinking too much current, and that usually means the primary winding has too low a resistance. The secondary coil produces a high voltage, but next to no current.

If you have a ballast resistor lying around, try sticking it in series with the primary winding (ignition to coil + terminal). Failing that, a 21W indicator bulb in series will present about 7 ohms of resistance, if I remembered my electrical theory right...

21W at 12V = 1.75A, Power = I^2 x R, I^2 = 3.06, 21/3.06 = R = 6.8 ohms)

I don't subscribe to the "lightning strikes twice" theory, so I will throw in this query, which is, why do you think the coil is overheating? It should be warm under normal operation, unless it is too hot to touch it might just be running normally?

Lauren

[Jerran]

So a little update, my 5M has been through a rather large rebuild, I checked the coil wiring and it seems the coil wires we not wired correctly. So I swapped them so that now the feed from the distributor goes to the negative side of the coil, the positive to the ignition switch. Took for a run today and ended up having to replace the condenser after a short run. Now have a new condenser and a correctly wired coil that bolted to the body.
Last year I'd been running the coil wired incorrectly the whole time!
Coil now seems to be cooler in operation. There doesn't seem to be a widely available electronic set up available for my ducellier set up so looks like I'll stick with points for now.

[Spacenut]

Ah, OK - the coil will work with the points connected to the + terminal, but in my experience (yes I have done it myself) the engine doesn't run very well, occasionally misfiring. I guess the coil could overheat as well. Glad to hear you have finally got to the bottom of the problem!

Lauren