MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Ballast Resistor wiring


Please can anyone help me with the wiring of the ballast resistor/Distributor. I have a Lucas ballast resistor which on the LHS has engraving saying "distributor" and 3 connections for spades; on the RHS side I have engraved "SW+" and " start" and 3 further spade connections; it is unclear which words line up with which conectors.

I have a Lucas 35DLM8 coil that has two wires coming out of it one black one red. As I don't want to short anything please can anyone tell me what connections I need to make to which specific terminal on the resistor/distributor/coil. I think originally there would of been a plug to the resistor but I don't have this.
R Weston

Normally the ballast resistor is a simple two-terminal device with one side connected to the 12v supply from the ignition switch or relay and the other side to the coil +ve. There is another wire from this terminal to the boost terminal on the solenoid. A 6v coil usually measures about 1.5 ohms on the primary and ballast about the same.

What does your coil primary measure, and what are the resistances between each pair of terminals on your resistor?

'SW+' could mean either the SW (old terminology) or +ve (new terminology) terminal on the coil, or the ignition switch. 'start' could mean the boost contact on the solenoid, but that is only guessing.

You know, it is amazing what you find on Google. Typing in '35dlm8' comes up with 55 pages, most of which say that '35DLM8' is a distributor and not a coil! It seems to be one of the electronic distributors, so correct connection of any resistors is pretty critical.
Paul Hunt

Thanks Paul for your input, I will check the resistance of the coil tonight. The 35DLM8 is an electronic - it is the one with the amplifier on the side of it (where the two wires come from). I made similar assumptions to you about the meaning of the engraving but on the LHS side (distributor) there are 3 spades but only two wires ( coming from the dizzy). On the RHS it is unclear which of the two spades I should use for the SW+ and start. If it helps the ballast resistor is about 100mm sq and is made of Aluminium (heatsink)
R Weston

Not sure if there is something wrong with my meter but taking the resistance across the two coil terminals gave a reading of 0.13 ohms. left to right accross the resistor gave readings of 9.5 K-ohms, 0.03 ohms and 28 K-ohms
R Weston

Richard,

Sounds like you have the standard lucas ballast pack.

I believe the 'limb' distributor is very similar to the earlier 35DE8 'opus' system.

If it is then only the two distributor wires are connected on that end, the other has power feeds from the ignition switch and the starter trigger line plus a signal return to the tachometer.

I don't have my rover SD1 manual hand at the moment but will check it tonight.

Regards,

Dave
Dave Brooke

Dave,

Thanks, if you can tell me which ones go to which termonals on the resistor that would be great. It doesn't show anything on this in my manual.

Cheers

RIchard
R Weston

Richard,

Unfortunately my factory SD1 manual predates the 35DLM8 distributor. Lucky for us though my haynes manual has data and a couple of wiring diagrams.

These show the two distributor connecting to the +ve and -ve terminals on the coil - no ballast unit !!!

A check against the Rimmer Brothers web catalogue backs this up with the ballast unit only listed for the 35DE8 Opus units.

Hope this helps....

Dave
Dave Brooke

Thanks for checking Dave, I guess I can try it but I know for a fact that when I saw this engine running it was conected up with this ballast resistor.
R Weston

U fitting this in OE GTV8 with a ballast resistor fitted in the loom ?
RMW

No Roger it is a 3.9 with an SD1 distributor. I did get it working last night (i.e. sparking) but now nothing - I fear the worst. As I have also made the connection now to the Hotwire EFI (which I guess it wouldn't of had as standard) I am wondering if I should just junk the lot and look for a 'normal' V8 efi set up.

One other related point someone might be able to comment on, would the lack of a good spark set up effect the operation of the efi? I was spinning the engine over with everything connected (including the efi to coil wire), with the spark plugs out but couldn't smell any petrol getting through (it is getting through to the fuel rail and returning to tank). This looks like another problem that will stop me starting the engine for the first time this weekend.
R Weston

Swopped out dizzy, coil and ballast resistor for a knackerd but working set and the engine started for the first time!!! Now just need to find a good distributor!
R Weston

This thread was discussed between 25/05/2004 and 29/05/2004

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now