Ballast Resistor Removed ???

[80 XKE]

I have had problems starting my 1962 3.8 OTS, not only from cold, but from hot too.
A sage XKE man looked under the bonnet, saw that the Coil was marked "12v System" and pointed out that a Ballast Resistor was normally only fitted with, say, a 9v coil.
This is all "double dutch" to me.



The lead was swopped from the Ballast Resistor to the Coil and it seems to have cured the problem.
Will it now be o.k.?
Why?
Any explanations will be gratefully received,
Thanks,
GT

[Heuer]

The S1 cars (3.8 and 4.2) should have a 12 volt un-ballasted coil. Fitting a ballast resistor where it is not required will cause all manner of running problems. So your sage was correct and the car will run perfectly without it. The ballast resistor drops the voltage from 12v to 9v but as your coil was expecting 12v to run it was producing a much reduced spark, hence the start problems. In a true ballast coil system the ballast resistor is switched out of circuit during starting and is switched into circuit during running to increase longevity of points and coil. The S1 has no such system so starting and running performance will have been reduced as there would have been only about 9 volts at the coil at all times. Bin the ballast resistor, it should not be there.

If you want to post pictures on the Forum follow these instructions: http://etypeuk.com/forum/viewtopic.php?t=850 and your photo will appear thus:

[Larry Wade]

David's dead on. Dump your resistor.

Two other things to consider:

How old is your coil?
How old are your sparkplug wires?

A neighbor recently changed the sparkplug wires on his 63 FHC: they were the original cloth covered ones! It was way past time.

Good luck,

Larry

[80 XKE]

David and Larry.
Many thanks for your posts which give me some confidence. I went for a short run last evening and all seemed to be well. Started instantly from both cold and hot!
I am off to Silverstone tomorrow for the Historic Sports Car Club Meeting, so that should be a good test.

[80 XKE]

I had a good day at Silverstone. Great weather, super cars.
I bumped into a mechanic of great renown. He started with Ronnie Hoare at Maranello, continued with Nigel Mansell and now looks after a eclectic range of performance cars. He said that all the Ferarris had Ballast Resistors and that some 12v. coils had a warning on them that BRs had to be used. He had come across situations where the coils had been burned out, not necessarily on Ferraris.
My confidence in my new arrangement was somewhat shaken by this new information. However, on Wikipedia I found the following :-

The term also refers to an automobile engine component that lowers the supply voltage to the ignition system after the engine has been started. Because cranking the engine causes a very heavy load on the battery, the system voltage can drop quite low during cranking. To allow the engine to start, the ignition system must be designed to operate on this lower voltage. But once cranking is completed, the normal operating voltage is regained; this voltage would overload the ignition system. To avoid this problem, a ballast resistor is inserted in series with the supply voltage feeding the ignition system. Occasionally, this ballast resistor will fail and the classic symptom of this failure is that the engine runs while being cranked (while the resistor is bypassed) but stalls immediately when cranking ceases (and the resistor is re-connected in the circuit).

Modern electronic ignition systems do not require a ballast resistor as they are flexible enough to operate on the low cranking voltage or the ordinary operating voltage.

I am now more happy having read the last paragraph. My car has electronic ignition so I should not suffer premature burn out (of the coil variety!)

Comments from the cognescenti will be welcome.

[Bill Molloy]

As they say "A picture paints a thousand words"

When the engine is cranking, the current flows along the thick red line (bypassing the ballast resistor) and giving max power to the Coil.

Once the engine is running, ie; you let go of the ign key, then the current goes up the thin red line instead, through the rev counter and the ballast resistor (which keeps the current low and saves energy) and stops the coil from burning out.

[Heuer]

Geoff

The principle of the ballast coil is as described in the Wiki entry you found. Using the starter takes a lot of juice so some manufacturers arranged to send 12volts to a 9v rated coil, in effect over-driving it to produce a healthy spark. This compensated for the voltage drop/current drain caused by the starter. Once the car was running a resistor (the ballast) was switched into circuit with a relay or a second circuit on the starter switch because over-driving the coil in this way would have dramatically reduced the life of the coil and points. Jaguar did not feel this system was necessary with the XK engine so went with the standard coil setup. Ferrari adopted the ballast system because their engines were highly tuned and temperamental so getting them started was an act of faith!

You can incorporate a ballast coil system into your car if you really want to (later cars used one) but it will mean modifying the wiring to suit. As you have electronic ignition it would be pretty pointless to do so though. If you are still worried I suggest you install a new appropriate Lucas Sports coil or Bosch Blue either of which is readily available from one of the usual suppliers. e.g. http://tinyurl.com/ogljd3 While you are at it worth getting one of SNG Barratts newly designed non-riveted rotor arms, if only to keep as a spare: http://tinyurl.com/qadsyz

Finally you might want to check over the rest of the ignition system as whoever put that ballast on (dealer, workshop, previous owner?) clearly is clueless about E-Types so you may find some other oddities

[Echezeaux]

Hi Geoff,

Do you know the brand of your electronic ignition ?
I have a CRANE Fireball 700 with a ballast resistor, and I can't find a wiring diagram about it since CRANE is not in business anymore.

Thanks in advance.
Thierry

[80 XKE]

Thierry

My car has a "Lumenition" optronic ignition system fitted. If you Google Lumenition you will find copious details.
I have taken the opportunity of reading through their literature and was re-assured to find the following:-

Positive Earth Vehicle Wiring.
Where vehicles have a ballast resistor fitted for ?cold start? operation the facility can only be retained if a separate relay is fitted. Should you wish to retain a cold start option Lumenition cannot supply any wiring diagrams or additional components that may be required. In practice the improved efficiency of the Lumenition Optronic system usually makes cold start facilities unnecessary

I think my"belt and braces" solution will be to keep a spare coil in the boot!

[Moeregaard]

Any car running a Mallory Unilite distributor will need a ballast resistor and appropriate coil as well. The optical trigger unit doesn't care for full voltage and will die an early death if given 12 volts. I realize that the 123 has eclipsed the Mallory in popularity, but I thought this worth mentioning.