Ballast Resistor?

[King Fisher]

It seems Nick's S may have chomped through another coil, so this time he's looking deeper into the problem. Someone suggested it could be the ballast resistor, but without the S Series book to hand, he can't find where it is. Can anyone help?

[MJG280]

Usually attached to one of the low voltage connections to the coil if it's a 2.8

Edited by MJG280 on Sunday 15th April 20:34

[King Fisher]

MJG280 said:

Usually attached to one of the low voltage connections to the coil if it's a 2.8

Edited by MJG280 on Sunday 15th April 20:34

It's a 2.9, but at least that's a start, thankyou!

[GreenV8S]

Is it actually a ballasted coil? Easy enough to tell just by measuring the voltage at coil +ve when the coil -ve is (briefly) earthed. If it dips to 6V ish, it's ballasted.

[Le TVR]

Its often tiewrapped to the upper chassis rail LHS of engine. Will be 1,3 Ohms.

[King Fisher]

Ok, cheers guys. Think he's going to measure the input to the coil with a multimeter. He was told 9 volts input is normal when running, and 12 volts when cranking?

[Le TVR]

Yes, 9 v when running, 12 v cranking (if battery is good!)
Ballast resistor is shorted out when cranking.

[King Fisher]

He got 13 volts to the coil when running? There is no sign of a ballast resistor anywhere on the feed to the coil either. The Steve Heath book shows a 'cold start resistor' on the wiring diagram, but there's no further info on where it may be located.

[BigRedTVR]

Hi - mine is just a long loop of wire - connected via bullet connectors - starting at front left of chassis (beside wheel) on main beam - looping across the front beam under the horns and back.

[King Fisher]

Just checked the Steve Heath book again; the generic wiring diagram for 'V6 engined cars' shows a cold start resistor (ie. ballast resistor), however, the wiring diagram for the 290S shows no ballast resistor. This is backed up the Haynes manual for the Sierra 2.9, showing it too has no ballast resistor. So it looks like perhaps the S2 onwards did away with the ballast resistor, and used a 12 volt coil?