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Ballast Resistor


In Fourth Gear
Can anyone explain what the Ballast Resistor does? can i get rid if i have the new type of glow plugs. it seems to get very hot and glow and i want the glow plugs to glow not the ballast resistor!!!

does it serve a perpose with the new type of glow plugs ie parallel or series wired.
Does that make them work better?
Lots. The old coil type plugs (wired in series) use about 4.7V (IIRC), whereas the new probe type should be wired in parallel and use 12V. When my 109 originally had its diesel transplant, the garage installed a balast resistor even though I was using a 19J - the heater plugs barely worked. On this rebuild, I left it out, and the engine starts within a second of turning the key - it makes that much difference!
Just bypass it, take the feed for the plugs from the input end of the resistor. It's purpose is to cut the voltage down so that the early style plugs do not burn out...you dont need it for the later style which are all 12v.
When bypassing the ballast resistor for using probe type plugs, earth the warning light wire that is on the output end of the resistor and replace the warning light bulb with a 12v item.:)
That's all great advice thanks.
about the earth wire earth to where? and my light does not work anyway do i need one? i should say that my heaters are wired to a seperate switch on my dash as my ignition does not work properly.

but will lose the ballast resistor. cheers all.
The warning light wire on the output end of the resistor is what Phil means... the thinner one of the two. Put that to earth, and fit a 12v bolt in the warning lamp, and it 'should' work. Maybe not though if the original wiring has been bypassed to a new switch.:) You dont necessarily need a warning light... nice to have though!

No need to remove the resistor though...just move the wire for the plugs from the 'out' end to the 'in' end of the resistor. It will work, and as it no longer creates a circuit, the resistor will not get used at all. (so it wont get hot or anything, it is redundant...but makes for a handy connection point for the rest of the wiring.)
Just had a look at them and i do not have any thin wire. just the main one to the resistor then from it to the plugs so i guess i will just bypass it.
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