Hello from Ireland

[Malcolm C]

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The Bristol lads are having a great time in Ireland doing the Gordon Bennett event
One of our members did have a big problem when his car caught fire.
The oil had exploded,setting fire to the engine.
He was helped out by lots of people i.e. fire extinguisher,and a lone off one the UK lads had a spare coil and a set of HT leads.
With a lot of work on the wiring he's up and running
Any one any ideals why a coil would explode
Malcolm

[Seaking]

Hi Malcolm sorry cannot helpwith why but hose that engine down and get rig of that extinguisher asap it can be corrosive

[V Mad]

The coil may have been overloaded. If you run a ballast type coil without a ballast they can get very hot.

[ChasR]

Hi and welcome to the forum. Quite a few chaps here should help you with your cause .

Incorrect wiring (lacking a ballast resistor) could cause this (as said above) but a number of the aftermatket oil filled coils on sale have been proven not to be so great.

http://www.british-cars.net/mga-bbs/another-exploding-coil-2010041820424025508.htm

[Malcolm C]

We found the cause of the coil blowing up,someone in the past had run a wire from the fuse box to the coil,so the coil was getting 12 volts,plus the 6 volts from the ballast resister,it a wonder the poor coil did not blow many years ago
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[V Mad]

We found the cause of the coil blowing up,someone in the past had run a wire from the fuse box to the coil,so the coil was getting 12 volts,plus the 6 volts from the ballast resister,it a wonder the poor coil did not blow many years ago

BALLAST BYPASS CAUSES FIRE: This sort of information is really important to get through to owners who may not be aware of this risk. We all need to check out cars when they are new to us.

Thanks to Malcolm C for the info.

[saxplayer]

if memory serves me correctly , is there a 12v feed from the startor solenoid to give 12v to the coil during engine cranking?
shaun

[Malcolm C]

Your correct,but the way this was wired was that it had a permanent 12v from the fuse box plus 6v from the ballast resister,then god knows how many volts when the engine was cranking

if memory serves me correctly , is there a 12v feed from the startor solenoid to give 12v to the coil during engine cranking?
shaun

[ChasR]

It's amazing some of the botchery you see, and then seeing these cars get a bad name. Kenlowe fan wire across the fuse box anyone (unfused)? It only blew half of the fuses if the fan was on for a while...

[73stagman]

Your correct,but the way this was wired was that it had a permanent 12v from the fuse box plus 6v from the ballast resister,then god knows how many volts when the engine was cranking

The significant fact is the 12volts permanent feed. The voltage s wont add up as they are connected in parrallel. Ie 6 volts from the ballast resistor 12 volts from the live feed 12 volts from the starter solenoid all just means that during cranking the 12 volts comes from the starter and then when the 6volts should be powered through the ballast resistor it is instead being fed 12 volts directly. (You wont read 30 volts at the coil when the engine is cranking as it was wired or with correct wiring 18 volts...) you will always only read 12 volts or 6 volts (sometimes 9 volts depending on the ballast resistor)
What happens especially in cheaper aluminium canned coils is that the oil gets warmer and warmer and expands as it gets hotter and so increases the pressure inside the can. If the pressure inside the coil can overcomes the yield strength of the crimping around the top it will just let go. As it does so it may be possible as in this case for the live feed to short out, spark and then light the hot oil.

[Malcolm C]

I am no auto electrician,but we had a multi tester and at the coil there 16 volts.

[73stagman]

With a (properly charged) 12volt battery system you should only ever see 12 volt maximum anywhere in the system with the engine off. (unless you have another battery (alarm backup system? wrongly wired in series)behaving like a 24 volt truck system) When its running you can see 14 to 15 volts (I think the theory value is 14.4 volts) because the regulator on the alternator (if it is internal then its factory set)switches the alternator on as the voltage falls and off once it has reaches the maximum. If you see much more than this then the regulator may be overcharging the system anyway. And so the problem with your coil is made worse because it would see the over voltage and so be even hotter.

A useful read http://www.familycar.com/Classroom/charging.htm

[SUTTY1]

Glad the cars sorted and hope the rest off the trip goes well!!!


A useful read http://www.familycar.com/Classroom/charging.htm

Thats a good link, easy to read and understand. If it wasnt copyright protected I would pinch some to use in the training centre I work in

[jleyton]

When its running you can see 14 to 15 volts (I think the theory value is 14.4 volts) because the regulator on the alternator (if it is internal then its factory set)switches the alternator on as the voltage falls and off once it has reaches the maximum. If you see much more than this then the regulator may be overcharging the system anyway.

During my recent 1000 mile trip to Belgium, my alternator was overcharging at about 15-17 v .

Although I reckon I'm pretty good with vehicle wiring, I'm hopeless when it comes to the detail of things like alternators.

I was therefore well pleased with myself when I removed and dismantled my alternator and swapped over the voltage regulator with one from an old alternator (kindly donated by Staginhiding) and it worked What's more, I amazed myself by only taking about an hour to do the whole job.

The lesson is, study first, as I was on the point of simply buying a new alternator.

Cheers

Julian

[Rubce]

Yes Mr Julian Teacher Sir. What homework assignment have you set for us this week? Chuckle. Bruce