free hit
counters
coil overheating - Engine/Ancilliaries - The Lotus Forums Jump to content
zeta

coil overheating

Recommended Posts

Hi,

about my elite '82, should be same as with the esprit, starts running bad and stalls after about 30 minutes, coil gets hot. renewed ignition coil with NGK u1056  / 48236. same problem. car did not drive for 3 months when this occured, before no problems.

checked for the ballast resistor, it doesn't have one. checked the resistor wire (white/pink one), it seems ok, not much to see. checked wiring, distributor cap seems ok. it has the lumenition.

what could cause the coil to overheat ? would it make sense to put a (extra) ballast resistor (9br) before the coil. or using another coil that doesn't overheat? the new NGK coil could just be bad of course, but before getting another one, something caused the old one to overheat, might have been age, but in that case strange the new one overheats aswell.

or any other suggestions?

many thanks !

 

Share this post


Link to post
Share on other sites

Upgrade today to remove Google ads and support TLF.

Use a voltmeter to check what voltage the coil is getting :thumbup:

Share this post


Link to post
Share on other sites

It gets about 10 v with contact on and when idling. When i start revving it rises up to 13 v.

Something with the lumenition? Would it make sense to put an (extra) ballast resistor before the coil?

Maybe Something wrong with the resistor wire? not much to see or check about the pink white wire.

Share this post


Link to post
Share on other sites

Obviously, it needs to get the correct voltage be it 6 or 12.

Share this post


Link to post
Share on other sites

Are you sure the pink/white wire is actually a resistor wire and not just a wire?

Share this post


Link to post
Share on other sites

The pink/white wire on my S1 is a resistive wire which supplies the low voltage feed to the coil. When you engage the starter the starter motor solenoid connects a live feed straight to the coil to give it more voltage to help with starting. If the solenoid was faulty it would get the full battery voltage all the time and would then overheat. Unlikely but possible and easy to check if your system is the same as mine.

Edited by Paul Coleman

Share this post


Link to post
Share on other sites

With the ignition in the on position but the motor not running pull the pink wire off the coil and measure the voltage to a good ground. It should be around 6v to 8v if it is a resistive wire (Pink with a white stripe I believe on the S1 Esprit) It should not be 12v if it is you don't have a resistive wire and probably need a 3ohm coil not a 1.5ohm coil. There is another wire connected to the + side of the coil from the starter motor as Paul mentioned. With the car in the on position but not cranking it should have 0v to ground, during cranking it should be 12v to give you a bit of a hotter spark while starting.

 

Checking the voltage across the coil with the car running will give you an averaged voltage on a DC voltmeter. The negative side of the coil is opened and closed as the distributor spins so your voltmeter takes the average of the voltage to ground and no ground. However it does give a hint, if it goes up to 13v when you rev the engine I would think you don't have a resistive wire, but its just a hint not a definitive answer.

 

Now assuming all that checks out my next bet would be the luminition, but mine melted into a pile of goop during an electrical fire and I now have a petronix so I won't be much help with that.

 

Good luck

Share this post


Link to post
Share on other sites

With the ignition in the on position but the motor not running pull the pink wire off the coil and measure the voltage to a good ground. It should be around 6v to 8v if it is a resistive wire (Pink with a white stripe I believe on the S1 Esprit) It should not be 12v if it is you don't have a resistive wire and probably need a 3ohm coil not a 1.5ohm coil. 

 

The voltage needs to be checked with the wire still connected to the coil, otherwise the voltage will be 12V whether its a resistance wire or not.

  • Like 2

Share this post


Link to post
Share on other sites

or can i just use a 12v non ballasted coil instead ?

it seems the resistor wire is not ok.

either a ballast resistor in between or maybe a 12v non ballasted coil (replace the 6v ballasted) i would think. will a 12v coil run on 9v when idling?

Share this post


Link to post
Share on other sites

or can i just use a 12v non ballasted coil instead ?

it seems the resistor wire is not ok.

either a ballast resistor in between or maybe a 12v non ballasted coil (replace the 6v ballasted) i would think. will a 12v coil run on 9v when idling?

 

I would be best to fit a ballast resistor, then you can leave the auxiliary contact wire from the solenoid connected as it is. This compensates for the lowering of battery voltage when the starter is cranking and taking large current, by bypassing the resistor.

Share this post


Link to post
Share on other sites

thanxalot, will try that.

does start easy without the auxilary wire connected to the solenoid right now.may not even need it then.

Share this post


Link to post
Share on other sites

Yes it should be OK other than when the weather is very cold and battery a bit tired when it might be reluctant.

Share this post


Link to post
Share on other sites

Ah yes Andy's right Voltage needs to be measured with the load connected to ground. I swear sometime my brain just isn't working! = )

Share this post


Link to post
Share on other sites

I've just been through this on my car, and the advice I got from a techie colleague (does tv station electronics, and races a hillclimb car...) is that if you're testing the coil voltage, don't do it with the engine running.  The voltage will be doing all sorts of strange things as the coil charges and discharges, and your multimeter will be doing its best to give a reading, but one that's possibly wrong.  

 

To verify this test the coil voltage running and not running, they were different on my car by 3v.  The reading without the engine running is the correct one.  

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×