Mustang Owners Club Australia Forum
Technical & General Discussion Area => Tech Torque Pre 1973 => Topic started by: matttyler on January 25, 2009, 07:01:37 pm
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Sorry guys need some tips.
I replaced the coil on the car with a GT 40R some two weeks ago. As per recomendation the type R needs an external resister.
The problem being after two weeks of use the coil has been cooked and is now stuffed.
Does this mean.
A. I have bought a dud coil and its just given in.
B. There is a possibility that at some stage the resister was removed and the car rewired to use a coil with a built in ?
Since I have had the car the only elec work has been a new Bosch alt as the old one gave up the ghost. The other reason I ask is that I can not see any evidence of a resister. Where should that be ? There are only three wires to the coil one earth. two poistive. One goes to the carb the other back into the ignition.
What would happen if I did install a coil with a built in resister ? Or stuff it all and take it to an auto elec ?
Thanks guys....
Matt;w
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My guess is that the previous owner has bypassed the resistor (which is just a pink wire wrapped in the loom under the dash), so is hard to find.
With the car running check the voltage between the +ve of the coil and ground. If you have 12 volts then the resistance wire has been bypassed, if you have about 7volts it is still in use.
cheers
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Thanks Nassi !!!! I dont have a voltage meter handy yet. But if I changethe coil to a built in will it stuff anything up ?
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I think you should get help!
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Ha Ha ........... with the state of the current mental health system I might struggle !!!!!!
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Matt, apart from a bypassed ballast resistor, there is one other thing that can cook a coil. Do you by any chance ever leave your ignition in the ON position without the engine running? If so, this can get it real hot (& potentially burn out) because the voltage is constant unlike when the points are opening & closing. Just a thought.
P.S. You'd better confirm that your ignition system DOES require the ballast. Many modern systems use a full 12V & require a suitable coil.
Evan.
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Ok Nassi. Hope you can help some more !!!!! I checked the reading at the poistive terminal it came up at 10.2 volts !!!! Not quite 12 not quite 7 Lol. What do you think ?
Ev. As far as the ign being on I havent left it on. Thanks anyway mate.
Cheers guys
Matt
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Was that with the engine running Matt? This is critical.
cheers.
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Yes it was mate !!!! At idol
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My number is 08 94961747 for the next 30 mins or so.
cheers
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Sorry Matt, not quite the outcome I expected.
cheers.
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Hi Mo.
Yeah sits in the same spot as yours did. I am going to an auto elec tomorrow to get it sorted.
Thanks guys for the tips. I love having a go at things cause thats part of the fun. A special thanks to Nassi. Mate you went over and above thankyou so much. If you ever need something in Adders I would be glad to help.
This is what makes this forum great :(
Cheers
Matt
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Originally posted by matttyler
Hi Mo.
Yeah sits in the same spot as yours did. I am going to an auto elec tomorrow to get it sorted.
Thanks guys for the tips. I love having a go at things cause thats part of the fun. A special thanks to Nassi. Mate you went over and above thankyou so much. If you ever need something in Adders I would be glad to help.
This is what makes this forum great :(
Cheers
Matt
Mate I hope to catch up next year for your nationals, we can have an ale or two.
cheers.
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Matt, it it shoult be at least 9 volt at the coil for that to to work. Recheck that you are getting at least 9 volt and take it back and jump and down.. I have another gt4oR if you are in Melb?
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Originally posted by Mac1
Matt, it it shoult be at least 9 volt at the coil for that to to work. Recheck that you are getting at least 9 volt and take it back and jump and down.. I have another gt4oR if you are in Melb?
Mac, are you saying that the 10v is ok with the resistor in use?
Just trying to get my head around this as I have measured them as low as 5.5 volts but generally a bit higher.
Whats your nominal value please?
cheers.
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Guys,
Went to the auto elec today. The upshot is that the resister has been by-passed. How he came to that is a little less clear !!!! He said that the voltage while the car is running at the coil can very from car type and is affected by the points opening and closing. He measured the volatage at start up. He said that was the most acurate and you should get a full 12v. In this case there wasn`t. Which he said indicated that the resister had been by-passed.
Now I work off logic. If the resister wasnt there wouldnt you get 12v easy ? Anyway he said swap the coil to a GT 40 not a GT 40R. We will see !!!! He only charged me 15 bucks if it stuffs up gain I will go back !!!
Clear as mud
Cheers
Matt
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The auto electrician is right to a degree.
When your car uses a resistor, you should have around 7v during running.
When you turn your key to start, the resistor is bypassed and you should have full 12v at the coil to give you a slightly better spark for starting.
However, if he tested this voltage while the engine was actually cranking, I'm not sure you would see the full 12v due to the load on the battery.
You're better off disconnecting the starter and measuring the voltage.
If you run a GT40R without a run resistor, then it will run very hot and may burn out.
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Yes, I found out the harder way by going electronic.
They need a full 12v system so I had to trace back the resistor wir (pink) to the ignition and rewire the feed. I had a low 9v but I'm not sure what the minimum potential difference should be, but too low and the spark has a hard time jumping and burning your fuel.
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Finally got to the bottom of the real problem !!!!! Thought this might be of interest.
The whole problem was not the resistor. It was a faulty solinoid.....spelling ?
Nassi you are correct. There should be only 7v approx running to the coil when it is running. When you kick her in the guts you should get the full 12v as mentioned above. The solinoid wasn`t fully closing which meant there was a full 12v running at all times !!!! Hence it burned points and stuffed the coil !!!!!
This pisses me because it was a brand new Scott Drake concors replacement ? All it did was burn the points, cook a coil and drain a battery and replaced a ignition..........Wasted heaps of time !!!
Just for interest sake I have swapped to elec ignition and it doesn`t matter what coil you run.
Thought I would post this so its now on the radar of potential problems. !!!!
Thanks again for everyones help.
Cheers
Matt
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Hi all,
Time to resurrect this post! I suspect my coil has died, car is cranking over but no spark.
Put a test light between coil points and no light when ignition is on or cranking. There is light between wire and earth however.
Now, I'm only assuming it is the original coil - the issue is I don't know about the resistive wire, did all 67's come with it standard?
So do I get a Bosch GT40 or GT40R?
I hope it isn't something like solenoid... car was running beautifully until it just didn't start on Sunday :(
Thanks in advance all!
Coops.
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According to Bosch application guide 289 Fairlanes/Falcons use GT40R or SU12R.
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Bump - could anyone help please?
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why mess around, just buy the right coil :thumb:..........
Steph has the original style ones.
http://www.custommustangs.com.au
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Thanks, but ideally I'd get the replacement to fix tonight from Supercheap or Autobarn - then I can drive down to Cooly Rocks On.
So I'm assuming as my coil is all-black and not yellow-top it isn't the original, so I should be able to use a GT40 or SU12?
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Is it your condensor giving you trouble ,that will stop your car starting ,with any coil the car will start and run ok,but if the wrong one is fitted it will burn out the points and condensor .
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It is funny how things can happen ,was at a friends house yesterday in my mach 1 ,car would not start the coil was dead just like that ,he had one so fitted it started 1 st time put mine back one no go ,got me .
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Shouldn't be condensor as it is only one month old. Checked last night and don't get any voltage across coil when ignition on or when cranking. I do get voltage between +ve wire from dash cluster and ground.
If I get a GT40 or SU12 it should be ok, I plan on going Pertronix sometime soon anyway.
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p.s. I replaced it (back in June) with a Bosch GT40R and its working a treat
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Do you by any chance ever leave your ignition in the ON position without the engine running? If so, this can get it real hot (& potentially burn out) because the voltage is constant unlike when the points are opening & closing.
Last week I went to change the time on my radio, I accidentally left the key in ignition, switched to ON.
The next day the car wouldn't crank over, I did a bit of googling and found others said what you have and I was worried I burnt out my coil but some others disagree saying since the engine isn't running there isn't any load on the coil. The coil will burn out if the engine is running and you keep trying to crank it over via the ignition - you hear that screeching sound.
I got a jump start from a neighbour and drove 90 minutes or so without a problem, kicked over first time when I stopped. It was only a flat battery, the coil as far as I know is okay.
I'm still wondering why the battery drained, there are no dash lights that light up when the ignition is in the ON position so what else caused it to drain?
s
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Your coil has two seperate coils in it. One is charged by the battery the the ground is cut (dropping the electromagnetic field) which creates electro-magnetic induction which converts a flash of 12 volts to 20000 volts (or more) that high voltage is moved down to the distributer and moved to each spark plug gap which ignites your compressed fuel/air. Power running to a coil will still use power and I have seen them in the past heat up and burn out because the energy in it is not being released.
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Power running to a coil will still use power and I have seen them in the past heat up and burn out because the energy in it is not being released.
Is it different with electronic ignition?
s
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Here's a run down on how it all works and wiring diagrams including electronic systems.
http://en.wikipedia.org/wiki/Ignition_system (http://en.wikipedia.org/wiki/Ignition_system)