Coil gets HOT and engine cuts out. 1984 F250

[Gary Lewis]

When the truck is running I'm getting 14.3 volts from the red wire going to the coil, (about what it is also putting into the battery).

Key on, not running I see 12.7 volts.

Does that sound normal?

Thanks.

Do you know German? If so, jein. That means yes and no.

14.3 volts going into the battery while running is about right, as is 12.7 at rest. But, you should not have 14.3 volts at the coil while running. Something is mis-wired.

You can see in the schematic below that the ignition switch is supposed to bypass the resistance wire in Start and send full battery voltage to the coil, but that in Run the power flows through the coil and the voltage gets dropped.

Did you adjust the new ignition switch when you installed it? Instructions for that are on the page at: Documentation/Electrical/Ignition and then the Ignition Switch tab.

[Starliner]

Do you know German? If so, jein. That means yes and no.

14.3 volts going into the battery while running is about right, as is 12.7 at rest. But, you should not have 14.3 volts at the coil while running. Something is mis-wired.

You can see in the schematic below that the ignition switch is supposed to bypass the resistance wire in Start and send full battery voltage to the coil, but that in Run the power flows through the coil and the voltage gets dropped.

Did you adjust the new ignition switch when you installed it? Instructions for that are on the page at: Documentation/Electrical/Ignition and then the Ignition Switch tab.

Thanks very much.

I did not adjust it when I installed it.

Thanks for the voltage info will pull up that tab.

I think I'm in the right direction.

I saw the scans you did in the resources section. Thanks, that must have taken some time.

This is an interesting issue to trace, the fact that the coil is getting alternator voltage, not battery voltage which would have passed through a regulator, (if I am saying that right).

[Starliner]

Do you know German? If so, jein. That means yes and no.

14.3 volts going into the battery while running is about right, as is 12.7 at rest. But, you should not have 14.3 volts at the coil while running. Something is mis-wired.

You can see in the schematic below that the ignition switch is supposed to bypass the resistance wire in Start and send full battery voltage to the coil, but that in Run the power flows through the coil and the voltage gets dropped.

Did you adjust the new ignition switch when you installed it? Instructions for that are on the page at: Documentation/Electrical/Ignition and then the Ignition Switch tab.

I will adjust the ign switch tomorrow. If that doesn't help, until I can track down the real issue, wouldnt a ballast resistor bandaid the issue for in the meantime?

Also, I will check to see if someone has accidentally bypassed the resistor wire or replaced it with regular wire by mistake.

[Gary Lewis]

I will adjust the ign switch tomorrow. If that doesn't help, until I can track down the real issue, wouldnt a ballast resistor bandaid the issue for in the meantime?

Also, I will check to see if someone has accidentally bypassed the resistor wire or replaced it with regular wire by mistake.

Yes, a Chrysler ballast resistor would work as a bandaid. But you won't have full voltage for starting so it might not start as easily.

But I seriously doubt anyone has removed the wire as it is deep in the wiring harness. However, they may have wired around it.

[Starliner]

Yes, a Chrysler ballast resistor would work as a bandaid. But you won't have full voltage for starting so it might not start as easily.

But I seriously doubt anyone has removed the wire as it is deep in the wiring harness. However, they may have wired around it.

OR, like you said, it might very well be a simple ignition switch adjustment which is preventing the use of the resistor wire!

[ArdWrknTrk]

OR, like you said, it might very well be a simple ignition switch adjustment which is preventing the use of the resistor wire!

Look at the diagram above.

You can ohm from the coil hot to the white/light blue of the ignition box plug.

I don't have the reading in my head, but it won't be 0, that's for sure.

The coil WILL get hot if you leave the ignition on, not running.

Once the field is saturated the windings have to dissipate that current as heat.

There's an awful lot of filament in that can.

[ArdWrknTrk]

Look at the diagram above.

You can ohm from the coil hot to the white/light blue of the ignition box plug.

I don't have the reading in my head, but it won't be 0, that's for sure.

The coil WILL get hot if you leave the ignition on, not running.

Once the field is saturated the windings have to dissipate that current as heat.

There's an awful lot of filament in that can.

Look at Matt's thread here: http://www.garysgaragemahal.com/#nabble-f63

He shows the pink wire wrapped up in the dash harness.

[Gary Lewis]

Look at Matt's thread here: http://www.garysgaragemahal.com/#nabble-f63

He shows the pink wire wrapped up in the dash harness.

Jim - Don't miss that he has 14.3 volts at the coil with the key in Run. Wait!

Starliner - Was that with the key in Run but the engine not running? Couldn't be 14.3 volts DC with the engine running as the duty cycle, the equivalent of the points opening and closing, would have it far less than that. Unless you are reading the ringing.

So, please confirm how you measured 14.3v at the coil.

[ArdWrknTrk]

Jim - Don't miss that he has 14.3 volts at the coil with the key in Run. Wait!

Starliner - Was that with the key in Run but the engine not running? Couldn't be 14.3 volts DC with the engine running as the duty cycle, the equivalent of the points opening and closing, would have it far less than that. Unless you are reading the ringing.

So, please confirm how you measured 14.3v at the coil.

Yes, I noted that.

A) I'd check the batteries in my meter. They use battery voltage as a reference, and a low battery will cause a high reading.

[Starliner]

Yes, I noted that.

A) I'd check the batteries in my meter. They use battery voltage as a reference, and a low battery will cause a high reading.

I read that 14.3 while running, measured off the hot connector splice.

You have all been great BTW.

I do see on that diagram where in the "on" position the voltage should drop via resistor wire. I thing Gary is right on, that I need to focus on ignition switch adjustment first.

High voltage readings with low meter battery is very good to know. I will say though, that the standing battery at 12.7v tells me it is correct. I will definitely use that knowledge in the future.

Also, I did sand down battery/solenoid connections and it may have helped, certainly couldn't hurt.