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Ballast coil - brown deposit on wires
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jessejazza



Joined: 18 Mar 2009
Posts: 75

PostPosted: Tue Jan 02, 2018 4:21 pm    Post subject: Ballast coil - brown deposit on wires Reply with quote

I've now had three classics with ballast coils which seem to leave a brown coating on the +ve wires on the coil. The insulation looks ok but when remaking connections I notice that there is a coating on the wire. Why is this? Is it that a previous owner has used a standard coil and thus higher voltage is going to the starter and whilst running. i notice that the cable tends to be rather rigid.

So far I have isolated them with heat shrink sleeving and used a standard coil with 12V supply from fuse box or ignition switch. I've not noticed that a ballast coil provides the advantage on starting that it's supposed to.

thanks
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Tue Jan 02, 2018 5:36 pm    Post subject: Reply with quote

Ballasted coils are designed to run from 7 volts. Under normal running conditions the extra 5 volts is dropped in the resistive cable connecting the ignition switch to the coil. When the starter motor is cranking the resistive cable is shorted out thus giving the full 7 volts to the coil (rather than under running a 12 volt coil with the reduced 7 volts during cranking.)

So under normal running the resistive cable will get warm dissipating about 10 watts ( 5 volts x ignition current). The warmth can cause discolouration of the insulation.

Peter
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1939 SS Jaguar 2 1/2 litre saloon
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jessejazza



Joined: 18 Mar 2009
Posts: 75

PostPosted: Thu Jan 11, 2018 1:34 am    Post subject: Reply with quote

Many thanks for the reply... I thought it warmed up somehow but wasn't sure.

Is a ballast circuit worth it then? It is supposed to aid starting in cold weather I gather. On the cars I have had it seems to make little difference. Thinking of the motor with the largest starter e.g. Series Landrover - I don't think a ballast circuit was ever fitted and they have had to start I some of the worst conditions of any motor.
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Thu Jan 11, 2018 10:51 am    Post subject: Reply with quote

There are times when I couldn't get a car to start on the motor but it would go on the handle so I think the ballasted coil is worth having.

Peter
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1939 SS Jaguar 2 1/2 litre saloon
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alastairq



Joined: 14 Oct 2016
Posts: 1950
Location: East Yorkshire

PostPosted: Thu Jan 11, 2018 12:01 pm    Post subject: Reply with quote

On Skodas [proper motor cars], of the rear engined sort.....the coil had a ballast resistor on the side...In effect, when the engine was running, the coil used a reduced voltage...however, when starting, the ballast resistor was bypassed, and the coil received the full 12 volts [or slightly less in practice]....thus, when starting, with the starter motor making big demands on the battery......the ignition got 12 volts.

I rarely had an issue starting under the most arduous conditions [I did a lot of Long distance reliability trialling in mine]..providing I took the right approach to the carburation. [Later, a quad set of bike carbs even cured that!]
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Churchill Johnson



Joined: 11 Jan 2011
Posts: 359
Location: Rayleigh Essex

PostPosted: Tue Jan 16, 2018 1:02 am    Post subject: Reply with quote

I think i have posted this before but in 1963 when Vauxhall released the new Viva ha i towed load's in during that autumn because they would not start not bad for a brand new model,but when we fitted a ballast coil it started on the button i even fitted one to my old F model victor that had a bad battery i used a flick switch and it fired on the first turn, i might add later Vauxhall's did away with the resistor and had a resistor wire in the loom...
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