Lotus Elan

ballast resistor

PostPost by: Ennva » Wed Jul 02, 2014 9:07 am

Okay, so to cut a long thread short, for last 5 months she basically wont start, I have had her running, but again mysteriously stops. So ready to throw tools everywhere.

On the new and old coil, under static ignition (not cranking) the coil reads 8.5 or 7.5 volts respectfully, the solenoid and battery are all showing over 12v. Does this therefore mean that I have a ballast resistor, logic would say yes as this was common by ford and adopted by Lotus.

I appreciate this is specific to me, but if it does have a resistor, it is not in the engine bay, any clues welcome.

Many thanks
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PostPost by: gjz30075 » Wed Jul 02, 2014 9:51 am

Certainly logic says there's a 'resistance' somewhere. It's possible to have a resistance wire, as Ford installed said wire in many of their cars in the 60s and 70s (in the US, anyway), maybe other times, too. In other words, the resistance wire is the ballast resistor. Has the wiring been changed sometime in the past?
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PostPost by: Ennva » Wed Jul 02, 2014 10:08 am

HMMMMMM...My father rebuilt the car 26 years ago and has ben suffering starting issues for some time. He does nt recall wiring in a ballast resistor either way. Ilike you thoughts on resisting cable, are there any easy ways of identifing this?
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PostPost by: rgh0 » Wed Jul 02, 2014 10:14 am

Do you have a resistance coil fitted?- they are normal stamped on the bottom with the reduced voltage rating.

The first test I would do is to run a wire direct from the solenoid active side to the coil and see if the car starts and runs. If this is the case then its definitely the reduced voltage preventing starting. Regardless you need to determine that the reduced voltage is intentional due to a ballast resistor or not intentional due to a bad connection somewhere in the system. if you have a ballast resistor you should have 2 wires to the positive side of the coil - one from the solenoid supplying the full 12 V when cranking and one from the ignition via the tach through a ballast resistor that supplies the reduced normal running voltage.

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PostPost by: gus » Wed Jul 02, 2014 11:05 am

It shouldn't have a ballast resistor, and does not need one.

run a piece of wire from any 12v source to the coil + if the car starts and run normally there is an issue with the coil feed

ignition switches die too
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PostPost by: Ennva » Wed Jul 02, 2014 12:15 pm

Rohan,

many thanks, i do not have two wires to the coil, that said with the lumention there was albeit that was direct power and tacho. I have changed the ignition switch, so I am thinking bad connection somewhere. I will try to connect via starting solenoid direct to coil and see if this helps. I assume to the White/red termial as attached?
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PostPost by: rgh0 » Wed Jul 02, 2014 12:20 pm

Use what ever terminal is always showing 12 volt. The brown does and I think the red / white one does also. The blue / white terminal is switched and only gives 12V when the starter is operating.

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PostPost by: Ennva » Wed Jul 02, 2014 12:46 pm

if in doubt go back to the person who wired it..........
After a very helpfull call to Mikriss finishes in stroud, I am informed he would of never wired it with a ballast resistor as they are too much trouble, what transpired was quite interesting, we discussed that the battery is only showing 400amps out of 700 on static, perhaps this is the problem after all, not enough juice ... will jump start tonight, or his other suggestion starter motor is giving up and drawing too much current. Any thoughts appreicated.
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PostPost by: billwill » Wed Jul 02, 2014 12:58 pm

Clearly not relevant to the original post now, but this message is important for any cars that do have a ballast resistor.


If the blue/white connector is missing on your solenoid, the only safe connection on the solenoid for applying full battery voltage to the ignition coil for test purposes is the Battery connector and its feedout the brown wire. This will bypass the ignition switch and the ballasat resistor.

The correct terminal to use is the one labelled blue/white, but it is not present on all solenoids.

It is supposed to be present on cars fitted with a ballast resistor The main point being that it is completely disconnected when the solenoid is not activated.

You can test briefly from the White red terminal or from the Black terminal, but do not leave it connected permanently to those. And the test result may be uncertain.

The white/red is the connection from the starter position of the ignition switch to the pull-in coil in the solenoid, if you connect this to the ignition coil, then when the ignition switch is in the normal running position there will be an unwanted back flow electric circuit through the ignition switch, through the ballast resistor into the pull-in coil. This may or may not be sufficient current to pull in the solenoid causing real problems, but will in any case reduce the current available for the proper route through the ignition coil and contact breaker.

The thick black contact is the high-current connection to the starter motor and is normally live only when the solenoid is pulled-in. if you connect this to the ignition coil, then when the ignition switch is in the normal running position there will be an unwanted back flow electric circuit through the ignition switch, through the ballast resistor into the starter motor. This will not be sufficient current to drive the starter motor, but will be more than enough to burn out the ballast resistor. If your ballast is in fact in the form of a ballast wire in the loom it will likely burn the wiring loom.
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