Ignition Ballast Resistor - Electronic Ignition

[Chilp3]

I have an early TR6 CR series (build date December 1972) fitted with a ballast resistor set-up within the loom. The car has had a ‘Neumonics’ electronic ignition system fitted around 2005 by ‘Enginuity’. The system requires a requires a 12v supply and teh car is currently fitted with a 12v coil. I have recently experienced a mis-fire after about half an hour’s normal driving which gets worse. However when I park the car and return a couple of hours later the mis-fire has gone. Sadly the same symptoms return again after around half an hour. I believe the problem maybe a failing coil which is why I have raised this post on the forum.

 

I have purchased a replacement 12v coil from TRGB which I plan to fit in due course. Before I fit the new coil I wonder if a fellow member could explain simply how I can check if the ballast resistor on my car has been properly by-passed when the electronic ignition was fitted. Unfortunately I am rather restricted in terms of my knowledge of vehicle electrics so an ‘idiot-proof’ method with step by step instructions would be very much appreciated. I realise that the car will work even if the ballast resistor is still in circuit although it will of course eventually damage the new coil. I understand the car would originally have had a 6v ballasted coil fitted when new.

 

I suspect that as the electronic ignition and coil have been working fine since 2005 it has most likely been properly installed and the ballast resistor by-passed although I would like to be certain. This of course assumes the coil is the problem!

 

Best Regards, Peter

 

 

[Jersey Royal]

I have an early TR6 CR series (build date December 1972) fitted with a ballast resistor set-up within the loom. The car has had a ‘Neumonics’ electronic ignition system fitted around 2005 by ‘Enginuity’. The system requires a requires a 12v supply and teh car is currently fitted with a 12v coil. I have recently experienced a mis-fire after about half an hour’s normal driving which gets worse. However when I park the car and return a couple of hours later the mis-fire has gone. Sadly the same symptoms return again after around half an hour. I believe the problem maybe a failing coil which is why I have raised this post on the forum.

 

I have purchased a replacement 12v coil from TRGB which I plan to fit in due course. Before I fit the new coil I wonder if a fellow member could explain simply how I can check if the ballast resistor on my car has been properly by-passed when the electronic ignition was fitted. Unfortunately I am rather restricted in terms of my knowledge of vehicle electrics so an ‘idiot-proof’ method with step by step instructions would be very much appreciated. I realise that the car will work even if the ballast resistor is still in circuit although it will of course eventually damage the new coil. I understand the car would originally have had a 6v ballasted coil fitted when new.

 

I suspect that as the electronic ignition and coil have been working fine since 2005 it has most likely been properly installed and the ballast resistor by-passed although I would like to be certain. This of course assumes the coil is the problem!

 

Best Regards, Peter

 

 

Hi Peter,

 

Heres how to check.

 

 

 

http://www.tr-register.co.uk/forums/index.php?/topic/32063-ballast-resistor/

 

 

http://www.vtr.org/maintain/ballast.shtml

 

 

 

Cheers

Guy

Edited May 9, 2013 by Jersey Royal

[RogerH]

Very interesting video clip - but is it wrong!!.

 

If the contact breaker is closed then the video is correct as a small current is flowing through the coil/contact breaker thus dropping the voltage over the ballast wire.

If the contact breaker is open then there is no current flow so all the 12V will be present at the coil +ve tag.

 

Simply run a wire from the -ve tag on the coil and short this to earth - then take your reading.

 

You will not have done any damage to the 12v coil but if you are running the EI at less than required volts it may run oddly.

 

Roger

[Guest ntc]

It is right as he used the car as ground Roger

[RogerH]

Hi Neil,

Indeed the system has been grounded - but it still depends on the state of the Contact breaker. if open then 12V at the coil if closed then 6v at the coil.

 

 

Roger

[Guest ntc]

Roger

The points have nowt to do with it last one on the right

http://www.google.co.uk/imgres?imgurl=http://gardentractorpullingtips.com/animate/ign2ani.gif&imgrefurl=http://gardentractorpullingtips.com/ignition.htm&h=292&w=640&sz=18&tbnid=yf-196EL42A_YM:&tbnh=55&tbnw=121&prev=/search%3Fq%3Dballast%2Bresistor%26tbm%3Disch%26tbo%3Du&zoom=1&q=ballast+resistor&usg=__z4Rj6H5mGMmyKQ1aliWLa4RXIm0=&docid=XPsy0gy2y6ioNM&hl=en&sa=X&ei=boSLUbX1N-me0QWZnIGIDA&sqi=2&ved=0CEYQ9QEwBA&dur=225

Edited May 9, 2013 by ntc

[peejay4A]

Roger is right. I don't follow what you're drawing attention to Neil. Points open, no current in the coil primary so the coil feed from the ignition switch will be at full battery voltage regardless of whether a ballast resistor is there. Assuming you use a high impedance voltmeter that is.

[Guest ntc]

Ballast Resistor: This is an electrical resistor that is switched in and out of the supply voltage to the ignition coil. The ballast resistor lowers voltage after the engine is started to reduce wear on ignition components. It also makes the engine much easier to start by effectively doubling the voltage provided to the ignition coil when the engine is being cranked.

[peejay4A]

No argument with that.

[RogerH]

Hi Neil,

I think we may be talking at cross purposes.

 

In the cruising condition the ballast resistor will have 12V at the switch end and a varying voltage at the coil end depending on the position of the C/B.

With the engine NOT running but with ignition ON you will have 12V at the switch end and a stable voltage at the coil (high or low) - because the C/B isn't opening & closing - it will be open or closed.

 

If the C/B was closed then a current flows through the ballast which drops the 12V supply down to 6V (ish). This is fed into the 6V coil to give a normal spark.

If the C/B is open then NO current flows. This allows 12V to be present through the whole length of the system - but nothing is working.

 

This is the same for any resistor - apply a voltage at one end and the same voltage will appear at the other. However if one end is grounded then you will only get 12V at one end.

 

The Moss video clip makes no mention of the C/B. So anybody trying to replicate what they are doing may come unstuck as the C/B needs to be open.

 

My main reason for doubting whether it will work or not is based on the fact that it is a MOSS video.

 

Roger

Edited May 9, 2013 by RogerH

[badshead]

Unfortunately I am rather restricted in terms of my knowledge of vehicle electrics so an ‘idiot-proof’ method with step by step instructions would be very much appreciated.

 

 

Peter

You may be more confused now , so try this:

 

1. Check voltage of battery with volt meter and make a note

2. Remove the wires from the negative side of the coil

3. Connect a temporary wire from the negative terminal of the coil to earth

4. Turn ignition on (nothing else switched on)

5. Now check the voltage on the coil, put red probe on + side of coil and the - probe to earth

6. If the reading is less than 80% of battery voltage there is probably a resistor in the system. If it is more than 80% you probably have a standard system

7. Remove the temporary wire and reconnect wires.

 

Bill

Edited May 9, 2013 by badshead

[Ragtag]

Perhaps I could propose an even more basic test. The original system had two feed wires, one providing 12v for starting and the other (the ballasted wire) providing 6v? (I thought it was 9v) for running.

 

If you have what looks like original wires to the coil, then it is unlikely that the required mdification has been carried out. If you have only one wire or one original and one new then it most likely has been.

 

You could always post up a photo

[Chilp3]

Good morning everyone.

Firstly thanks for everyone taking the time and trouble to respond to my questions, much appreciated. I shall be having a go at establishing exactly what Enginuity did to my TR back in 2005 when they fitted the electronic ignition based upon your suggestions! I have now received a Lucas performance 12V coil provided by TRGB which I plan to fit at the weekend.

 

In the meantime, I have tried unsuccessfully to add a picture of the coil, appears the photo is too big. It appears to have two single yellow wires connected to either side as I described fro the original post, one from the loom and the other from the electronic ignition. Obviously with my loom being 40 years old there is probably an element of ageing and fading to be considered although to my eyes the wire from the loom certainly appears to be yellow!

 

In closing when you all refer to the ignition being 'on' for the test I assume you mean with the ignition light showing and not with the engine physically running? Looking at the posts I think it should be with the ignition light on and not the engine running but I thought I would ask for the avoidance of doubt.

 

Best Regards, Peter

[RogerH]

Hi Peter,

Ignition light glowing, engine not running. The loom 'yellow' wire is probably faded 'white'.

 

Roger

[jobster]

since your car is fitted with a 12v coil, I don't see any use for it, I would take it off. I did, and the car runs and starts excellent (123ignition).

[peejay4A]

Peter wants to check to see if the ballast has already been bypassed.