No power to coil

[Duane]

Any auto sparky experts out there?

I am trying to get my V8 project to fire up, but have no voltage on the WY wire to the +ve terminal on the coil with ignition on. When I crank the starter I get maybe 8V. I can only assume the ballast resistor is open circuit, but have no idea where to look for it.

Does anyone know exactly where it is in the loom? Is it simply a resistor or some little black box?

To test me theory, can I bypass it by simply connecting a new wire from an ignition live feed to the coil to test my theory? I have fitted an electric fuel pump so there is a power source right there.

BTW there is 12V on the white wire coming out of the ignition control fuse in the fuse box. The wiring diagram says this splits to the WY wire.

Is there anything else on this circuit that I can check has power or not?

 

[quattro]

It's a resistor wire somewhere in the loom. I have never managed to find it tbh.

If you want to test it, you can just run a 12V feed to the coil but I wouldn't run it for long as the coil isn't designed for 12V.

 

[jp928]

When cranking coil power should bypass the ballast resistor, so you should see closer to 12V then , unless there is a bad contact somewhere in that circuit, as long as the battery is in good condition. In theory my car (74, D chassis) should have a ballast, but I see full 12V at the coil when on, but not cranking - Lucas DLB101. No starting or running problems.

 

[Per-Anders]

How to test the ballast resistor:
Ballast Resistors, Resistance and Coils

 

[Duane]

Thanks guys. I think the fact I have no voltage on rhe WY wire when the lgnition is on means I need to check the wiring from the fuse box first.
The car has been off the road since 2008 so it could be a corroded terminal somewhere.

 

[jp928]

Duane, read the threads about S2 fuse panel issues for some hints about what goes wrong there. Some of the contacts are dependant on the state of the fuse next door. Mine had started to melt at the headlight fuses, but have now added relays there. I recommend removing the fuses one at a time, clean ends (dishwashing scouring pad), apply Deoxit, refit.
Did anybody who read the piece by simonbbc linked to above find it curious? The opening sentence, to me, is just strange - so incomplete as to be misleading - a ballast is an electrical device to reduce volts and increase spark??? And, if you measure the volts at the coil +ve in a car with a ballast, will you really see 12v until you earth the -ve terminal???? I see 12v at the +ve terminal, and the coil is a 3 Ohm DLB101, starting and running are good - no ballast?

 

[Duane]

Hi Guys,

I am really struggling with the wiring in this 75 V8.

I opened up the dash and had a look at the rear of the fusebox. Pic attached. Is it just me or are there wires missing from 9 and 17? There are fuses in these holders, but there are no unterminated wires anywhere? All fuses seem to be contacting properly.

Also I found when the ignition is on this Pink and White white is burning. There is no reference to a pink and white white wire on the wiring diagram, but it is connected behind the passenger side dash to the thinner white wire from terminal 19, then runs into the engine bay and is connected to a White and Yellow wire down by the coil (see pic). So it is a fused feed that connects to a White/Yellow wire by the coil. The white and Yellow wire then goes back inside the car to god knows where (ballast resistor maybe). I suspect this is why there is no power to the coil when the ignition is on.
I note there is also a White/Yellow wire on the diagram that goes from the cold start warning light to the cold start switch. I don't know if my car has that?

Anyone know what this pink/white wire is? And why it might be fried?

Also I have no side/tail lights.

I don't know if I have a combination of problems here or simple a short somewhere that is buggering everything up.

 

[jp928]

speaking for my 74 S, from its wiring diagram. Note that some fuse points have inter links, sideways. My diagram shows 9 (10?, instrument panel) is fed from 7-8 , which is side and tail light LH and number plate lights. The attached is a diagram of the inter or cross connects , may be useful. The way the fuse box is built means ALL fuses need to be present and making good contact on the ends for cross connects to work. The odd numbers are the input side of a fuse, output is the even no. Cannot find a plain pink wire in mydiagram.