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Overheating Coil on Bedford OY?


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Hello Mate,

I have a classic car shop near me, and i just ask for a standard 12 volt coil. The mw has run ok on them. You just need to make sure you don't get a more modern 9 volt coil.

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Thanks guys that is exactly what I got off a good friend. But alas that has not done the job :cry: . I drive 1100 yards or so and the coil gets incredibly hot and of course breaksdown. I have also now changed the condenser and checked the points gap and that all seems fine. Any suggestions?

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Thanks guys that is exactly what I got off a good friend. But alas that has not done the job :cry: . I drive 1100 yards or so and the coil gets incredibly hot and of course breaksdown. I have also now changed the condenser and checked the points gap and that all seems fine. Any suggestions?

Ballast resistor??

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Thanks guys that is exactly what I got off a good friend. But alas that has not done the job :cry: . I drive 1100 yards or so and the coil gets incredibly hot and of course breaksdown. I have also now changed the condenser and checked the points gap and that all seems fine. Any suggestions?

 

Check the ohms of the coil, it should be about 3 ohms for 12 volt standard coil or about 1.6 ohms for 6 volt standard coil.

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  • 2 weeks later...

I posted an earlier thread on the subject and agreed with all that posted that it looked like the coil had well gone off its mortal coil so to speak. Well we changed the coil and to be on the safe side we changed it the condensor as well and checked the points. We set off back to our secret lair were she is stored and got no more than 400 yards when she died. Upon inspecting the coil was so hot you could have fried eggs on it! We have gone through several coils now just to be sure that it was not another duff one. We have checked the voltage in the circuit and it is charging the battery around the 13v mark so we know the regulator is fine. :nut:

 

What is wierd is that when we run her at high tick over the coil doesn't even get tepid!I am now at a loss as to what the hell it could be! Whoever gets the answer to this one I will drive over and buy them a beer of their choice as we are all at a bit of a loss. :cry:

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I posted an earlier thread on the subject and agreed with all that posted that it looked like the coil had well gone off its mortal coil so to speak. Well we changed the coil and to be on the safe side we changed it the condensor as well and checked the points. We set off back to our secret lair were she is stored and got no more than 400 yards when she died. Upon inspecting the coil was so hot you could have fried eggs on it! We have gone through several coils now just to be sure that it was not another duff one. We have checked the voltage in the circuit and it is charging the battery around the 13v mark so we know the regulator is fine. :nut:

 

What is wierd is that when we run her at high tick over the coil doesn't even get tepid!I am now at a loss as to what the hell it could be! Whoever gets the answer to this one I will drive over and buy them a beer of their choice as we are all at a bit of a loss. :cry:

 

are you fitting the correct voltage coil. If it for use with a ballast resister it will be a 9v coil and will overheat very quickly, a coil off most late 50s early 60s cars ie. mini 1100 ect will work but not escort viva ect these had a resister. Try an old spares dealer as they understand the problem. best of luck.

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High resistance in the plug leads/caps?

That is what I am beginning to think. I am considering replacing all the HT leads. When it first failed there was considerable discolouring on each end of the HT lead and the cap to coil. It infact look as if it had got very hot too.

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  • 4 years later...

Reviving this thread to ask if you fixed the problem, and if so, how?

 

My OYD was cutting out after short runs. I fitted a new standard 12v coil and moved it off the engine block where it was mounted previously. Had it ticking over and it cut out after about 20 mins from stone cold. Coil was very hot. Points and condensor are okay. Leads and caps are quite recent.

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Reviving this thread to ask if you fixed the problem, and if so, how?

 

My OYD was cutting out after short runs. I fitted a new standard 12v coil and moved it off the engine block where it was mounted previously. Had it ticking over and it cut out after about 20 mins from stone cold. Coil was very hot. Points and condensor are okay. Leads and caps are quite recent.

 

Have you got the LT connections on the coil the correct way around? An OY has Negative earth so the wire from coil to distributor should be on the Neg - terminal of the coil. The feed from switch to Pos +.

 

Something else, the coil might be for a 12v system but perhaps is designed for vehicles using a ballast resistor. Best to make absolutely sure.

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Negative earth, coil is correctly wired.

 

Points gap 10 thou, plug gap 40 thou, timing spot on. Now idling very well. But coil too hot and cuts out after a while and will not re-start. After pouring cold water over the coil it will fire straight up again.

 

Coil is a standard 12v from a specialist who confirmed with me it was for a non-ballast system. The previous 12v coil acted exactly the same.

 

My next step is to fit a ballast resistor to see what happens.

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Negative earth, coil is correctly wired.

 

Points gap 10 thou, plug gap 40 thou, timing spot on. Now idling very well. But coil too hot and cuts out after a while and will not re-start. After pouring cold water over the coil it will fire straight up again.

 

Coil is a standard 12v from a specialist who confirmed with me it was for a non-ballast system. The previous 12v coil acted exactly the same.

 

My next step is to fit a ballast resistor to see what happens.

Hi , I had coils that would heat up very warm this year in Normandy of all times and places with seven other family members unboard. I had lots of spares and changed coils, plugs, points, condensers, rotor arms but eventually located a dirty negative terminal on the battery! There was sparks jumping from the high tension coil lead to one of the low tension terminals at the coil when i gave it a quick rev. I removed the rubber sleeve on the end of the lead as it seemed to be helping the spark to escape and as I said, cleaned the negative terminal connections on the battery and cable and thankfully all was well. You might have the same problem. Might be worth having a look at .Good luck . let me know how it goes. I have had a few of these issues before with the OY.

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Can you measure the resistance of the primarily winding and verify it is about 3 ohms? Or measure the current drawn through it is no more than 4 amps with the points closed.

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Another possibility that occurred to me is that some Bedfords have the distributor type where the whole body turns during the vacuum advance, In order to get a good grounding, there is an earthing lead from the distributor casing to a suitable earthing point on the engine block. If this is broken I wonder if it sets up a resistance in the Low Tension side of the coil ?

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Thanks, I'll look at that, I spotted a couple of earths in the engine bay that could be better, one near the generator.

 

Weird though, to me if a battery lead is good enough to pass about 400 amps to the starter it's good enough to trickle a little bit of current to the coil!

 

I'll have to have a look at it running in the dark to check for spark leakage.

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Weird though, to me if a battery lead is good enough to pass about 400 amps to the starter it's good enough to trickle a little bit of current to the coil!

 

I'll have to have a look at it running in the dark to check for spark leakage.

 

It is from the coil to distributor and thus to earth that I was describing, if it is the type of Distributor that I described, without the link lead from its body to the block there could be a resistance. You will unlikely see any sparks though, unless you are referring to the HT side.

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Sorry for the confusion, I was answering an earlier post to yours Richard. I did consider distributor earth so attached a new wire to a points mounting screw, passed through a hole drilled in the body, and took it straight to earth at the battery as a test. It made no discernable difference.

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