Ballast Resistor

[hbr341]

Hi
Has anybody got any idea why I have got to high voltage after the ballast its at 10-11 volts there is 14 coming in with the engine running on the white wire from the ign switch I have tried everything to try and sort it ive had three different ballast resistors coils changed and tested everything even set it all up on the bench with the distributor in the vice earth onto battery did all the three tests that it shows in the workshop manual on test b the middle one I only get 4.5 volts after the ballast with the 12v coming in from ign switch I have spent days trying to get it sorted cleaned all the earths and connections been over it all with a fine tooth combe good job iam at home.

Regards Chris,

[droopsnoot]

If you're measuring it while the engine is running, I don't think you'll get a proper reading. I had a similar thing on my Sportshatch, I'm trying to remember whether it was exactly what you're describing.

ETA - found it. The thing I described was "But, if I leave the [Crypton] machine connected and measure the coil voltage when the engine is running, it's showing 9.5V or thereabouts. I thought it was supposed to only be 6v. Is this 9.5v reading something to do with the effect of the coil running?"

I did some research and found that, with the ballast resistor in place and the points closed, I'd get 6v, and with the points open, I'd get closer to 12v. This suggests that while the engine is running, it will switch very quickly between the two and most meters will not be able to keep up, and will show somewhere in between.

[hbr341]

Hi
Thanks that would make sense I have got a 1256 HC so I ran the same tests on that and it was the same as the HB points closed got 4 volts after ballast and 11 volts running one thing I did notice after about 10mins running the ballast resistor is hot to the touch is that normal as it gets 14volts with the engine running.

Regards Chris.

[droopsnoot]

I wondered about heat, and I was told that as the resistor is changing voltage, it's inevitable that some heat will be produced.

I had the issue with the ballast wire that is part of the HC loom, and as I'd just done some repairs to the dash loom on mine I was concerned about it getting warm. I by-passed the loom resistance wire and fitted a ballast resistor in the engine bay, and now I don't know if it gets warm, and if it does, it's bolted to the top of the engine where it's warm anyway.