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    Super hot coil

    Anyone know how hot a coil is supposed to get? And if it’s not supposed to get hot, then anyone hazard a guess as to why mine is scorching?

    Thanks!
    Only the important people have signatures.

    #2
    You have a 6V coil when you need a 12V one?

    They do normally run quite warm, ( I would estimate around 55 to 60C) and can pick up a fair amount of heat from the valley, too.
    Header tanks - you can't beat a bit of bling.

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      #3
      Thanks. I’ve definitely got a 12v one! But it’s hot with the ignition on when the engine isn’t even running..
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        #4
        If the engine stops with the points closed then current will flow through the coil and heat it when the ignition is on. It is not usually a good idea to leave the ignition on with the engine stopped for long periods, as it does/can overheat the coil.
        Header tanks - you can't beat a bit of bling.

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          #5
          Originally posted by wilf View Post
          If the engine stops with the points closed then current will flow through the coil and heat it when the ignition is on. It is not usually a good idea to leave the ignition on with the engine stopped for long periods, as it does/can overheat the coil.
          Thank you, really appreciate your advice.

          I was fixing and testing my wipers and had no coolant, so didn’t want to start her up!
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            #6
            Originally posted by Chix View Post

            Thank you, really appreciate your advice.

            I was fixing and testing my wipers and had no coolant, so didn’t want to start her up!
            If you need the ignition on for a while without the engine running pull a wire off the coil to prevent damage.

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              #7
              Hello, I removed the coil from its (hot!) position in the V and relocated it on the rhs inner wing. If it gets too hot to be touched by hand, there is something wrong.... Dieter.

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                #8
                I’ve just investigated further... I have a 6v coil (probably original Stag one) but running a v6 Ford Essex. The voltage at the coil reads 12 on my multimeter, am I running the wrong coil??
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                  #9
                  6v coil is correct if you have the wiring as originally intended. This supplies 12v to the coil when the starter motor is cranking, but 6v once started. Who knows what has been done to the wiring in the past.....
                  Dave
                  1974 Mk2, ZF Auto, 3.45 Diff, Datsun Driveshafts. Stag owner/maintainer since 1989.

                  Comment


                    #10
                    Originally posted by DJT View Post
                    6v coil is correct if you have the wiring as originally intended. This supplies 12v to the coil when the starter motor is cranking, but 6v once started. Who knows what has been done to the wiring in the past.....
                    Thanks Dave. So if I put multimeter on during crank and during running, I should see 12v and 6v respectively? Thanks
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                      #11
                      Normally nearer 8v when running I find, but the alternator will be pushing the voltage up to 13V or more when the engine is running. Since you have a mk1 it should have a seperate ceramic basllast resistor rather than the in loom resistance wire of the mk2s

                      Neil
                      Neil
                      TV8, efi, fast road cams and home built manifolds. 246bhp 220lbft torque

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                        #12
                        Originally posted by flying farmer View Post
                        Normally nearer 8v when running I find, but the alternator will be pushing the voltage up to 13V or more when the engine is running. Since you have a mk1 it should have a seperate ceramic basllast resistor rather than the in loom resistance wire of the mk2s

                        Neil
                        I do have a Mk1, but the engine is a Ford V6.
                        I’m getting pretty confused as to what is triumph specific and what is Ford, to be honest!
                        id have thought that the coil is engine specific, so may need a different one to the 6V internal ballast Lucas performance one that I’ve got... but how do I find out which one I need?

                        Only the important people have signatures.

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                          #13
                          First thing, do you have an external ballast resistor?

                          As Neil says, if your car was originally a MK1, then it wouldn't have the ballast resistance wire in the loom.
                          Header tanks - you can't beat a bit of bling.

                          Comment


                            #14
                            Coil is not really engine specific, you might need a higher performance coil for a V8 vs a 4 cylinder as it needs twice as many sparks, but in general the only major difference between coils is ballasted or non-ballasted.

                            As Wilf says MK1 Stags had a ballast resistor clamped to the coil where as later ones had a resistance wire in the loom itself.

                            Is there actually a problem with the car running/starting or was it just the fact that it got very hot while you were testing the wipers?

                            To check if you have a ballast resistor or not disconnect the wire from the coil to the distributor and then run a wire from the coil to earth. Turn on the ignition and then measure the voltage on the coil. Full battery volts (approx 12.7v) means no ballast, and half battery volts (approx 6.3V) means there is a ballast resistor fitted. Do this as quick as you can nad don't leave the power on the coil for too long as it will over heat.

                            The reason the coil gets hot if current is left flowing through it all the time is that under normal running conditions the current is turned on and off so the average current is a lot less. The heat generated within the coil is governed by a "square law" (I^2 x R) so twice the current means four times the heat generated - which is roughly what happens when you leave the ignition on and the engine is not running and the points are closed - hence your very hot coil. Most modern electronic ignition units prevent this. Having said all that coils do get hot anyway, even when mounted on the bulkhead away from the engine.

                            Your initial check of 12v on the coil is meaningless unless the points were closed as there would be no current flowing through the coil.

                            Roger

                            White TV8 BW35 no mods and now a Dolly Sprint to keep it company
                            So many cars, so little time!

                            Comment


                              #15
                              Originally posted by marshman View Post
                              Coil is not really engine specific, you might need a higher performance coil for a V8 vs a 4 cylinder as it needs twice as many sparks, but in general the only major difference between coils is ballasted or non-ballasted.

                              As Wilf says MK1 Stags had a ballast resistor clamped to the coil where as later ones had a resistance wire in the loom itself.

                              Is there actually a problem with the car running/starting or was it just the fact that it got very hot while you were testing the wipers?

                              To check if you have a ballast resistor or not disconnect the wire from the coil to the distributor and then run a wire from the coil to earth. Turn on the ignition and then measure the voltage on the coil. Full battery volts (approx 12.7v) means no ballast, and half battery volts (approx 6.3V) means there is a ballast resistor fitted. Do this as quick as you can nad don't leave the power on the coil for too long as it will over heat.

                              The reason the coil gets hot if current is left flowing through it all the time is that under normal running conditions the current is turned on and off so the average current is a lot less. The heat generated within the coil is governed by a "square law" (I^2 x R) so twice the current means four times the heat generated - which is roughly what happens when you leave the ignition on and the engine is not running and the points are closed - hence your very hot coil. Most modern electronic ignition units prevent this. Having said all that coils do get hot anyway, even when mounted on the bulkhead away from the engine.

                              Your initial check of 12v on the coil is meaningless unless the points were closed as there would be no current flowing through the coil.

                              Roger
                              Thank you, this is really helpful. I know that the coil is definitely a 6V with internal ballast, as I have the details of it. But I don’t know what coil SHOULD be in there!

                              In terms of performance, she has been running fine but recently, after initial start up, has been lurching all over the place. I thought it was a fuel issue, but fuel is getting in fine. Which lead me to it being electrical maybe... the problem seems to gradually go away over the space of about 30 mins, which made me think it was because the engine needed to warm up, but then if parked for an hour, engine still warm, the problem starts again and when I put my foot down the engine sounds different and there’s no power or intermittent power, especially when going up hill and engine under strain.

                              Im going to check the spark plugs as previously suggested, I’ll keep you all posted!
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