Ballast resistor

[hloomis_7_1_1]

I have a question about the wiring, On my wires that go to the starter I have a white wire from the starter relay that goes to the starter, does the wire from the ballast resistor go to the coil first then to the starter or from the resistor to the starter also does it connect to the same male lug that the wire from the starter relay hooks to. The diagrams I have are not specific as to how they should go and where to hook them up.
Thanks in advance,
HL

 

[hloomis_7_1_1]

I guess no one knows anything about ballast resistors for MGB's and how they are wired.

 

[David_DuBois]

HL - Go to the Advance Auto Wiring web site at: https://www.advanceautowire.com/ scroll down and click on Stock Schematics, then on MGB. Scroll down to the year of your car and you will have a pretty clear drawing of how the ballast resistor is wired.
Cheers,

 

[hloomis_7_1_1]

Dave, I have looked at both diagrams for 73 and 74 #16 and #17 and I do not see any ballast resistor in either diagram however on # 18 the one for 75 and 76 there is a resistor in that diagram and a second lug on the starter to attach it to that I don't seem to have on my starter solenoid. The car I have is a 74 CB GT and had a resistor mounted next to the coil when I bought it, but it has been so long ago I don't remember if it was hooked up correctly or not I do know the car started and ran because I moved it around the driveway before I started the restoration work. I need someone that has a 74 to tell me if they have a ballast resistor or not and if they have a solenoid that has a second lug for mounting, if that is the case then either I have the wrong starter or I don't need a ballast resistor.
Thanks

 

[Cottontop]

Let me start by saying that I know little or nothing about MGs, but I do know a little bit about general automotive electrics.

In all cars that I know of that have a ballast resistor, the ballast resistor is wired between the ignition key and the coil positive.

The purpose of the ballast resistor is to protect the points from being burned and the coil from being overheated IF one should leave the ignition ON when the points happen to be closed. In that case, the ballast resistor, NOT the points or coil, will absorb and dissipate the bulk of the current and heat. The ballast resistor also drops the operating coil voltage from a full 12 VDC down to 7-9 VDC.

Most cars with an external (NOT mounted no the starter) starter solenoid also have a wire that runs from the small (I) terminal on the solenoid to the coil positive. This wire bypasses the ballast resistor and provides a full 12VDC to the coil to provide a hotter spark during starting. This wire may also be connected to the heavy starter wire if there is no I terminal.

That also may be the way the MG is wired. If not, forget what I said.

Tim

 

[David_DuBois]

Harry - Look at page 18 for the 75-76 MGB. That show how the balast resistor needs to be hooked up to work properly.
Cheers,

 

[hloomis_7_1_1]

Thanks for the help , the other lug on my starter was there but it got mashed down and I didn't see it. All is well now.

 

[Cottontop]

All is well now.

Just for my edification, <span style="font-weight: bold">HOW</span> is the ballast resistor wired ?

Tim

 

[hloomis_7_1_1]

Cottontop, it is just as the Advance wiring diagram on page 18 for the 75-76 MGB. https://www.advanceautowire.com/

 

[Cottontop]

it is just as the Advance wiring diagram on page 18 for the 75-76 MGB.

It appears as if it is wired exactly as I described.

The resistance wire from key to coil and a bypass wire from solenoid to coil.

Wow... NOW I actually know something about MGs.

Tim