Fun with electrons....

[Jbird]

I'm working on a 57 chevy, it has an aftermarket wiring harness and a three wire internally regulated alternator. When I sorted out the wiring and got it charging I discovered that everytime I shut off the engine the starter would engage momentarily, just enough to zing the ring gear. If I unplug the exciter wire it shuts off like normal.  I'm thinking there's a problem with the new reproduction ignition switch OR I need a diode in the exciter wire. Team Smart, rescue me!!    Jbird

[Bugpac]

This is the best i can do on a rescue....

[enjenjo]

Well, I'm not on team smart, but I would guess that a diode or a light bulb in the exiter wire will fix it.

[EMSjunkie]

Well, I'm not on team smart, but I would guess that a diode or a light bulb in the exiter wire will fix it.

Whadda ya mean, yer not on the Team :?:  :?:

you are our Technical Advisor  


Vance

[crdnblu]

I'd give the manufacturer a call, even if you didn't buy it from them.  Most of the wiring harness company's tech folks are really quite helpful.  Check the Net for contact info & numbers.

[Jbird]

Thanks Frank, now it has another little red light for the owner to wonder about.

Bugpac, thats one strange lookin donut.

Vance, I'll give you a bit of technical advice. Steer clear of enjenjos' place when lawn mowin season starts

Jbird

[UGLY OLDS]

Well, I'm not on team smart, but I would guess that a diode or a light bulb in the exiter wire will fix it.

Whadda ya mean, yer not on the Team :?:  :?:

you are our Technical Advisor  


Vance

And resident good guy that resolves things that go "Clank" ..Or "Clunk"..
And even "WA-WA-WA" & "Boo-Hoo-Boo-Hoo"  on occasion....    

[PeterR]

I discovered that everytime I shut off the engine the starter would engage momentarily, just enough to zing the ring gear. If I unplug the exciter wire it shuts off like normal.

I am guessing this a combination of two oddities.  

Certainly sounds like power is being fed back the exciter wire, but that alone normally makes the engine continue running without influencing the starter.

I suspect there is feed from the starter solenoid to by pass the ignition ballast resistor during cranking and that has not been set up correctly.   Run a temporary wire about 5' long from the START connection on the solenoid so you can monitor the voltage without having to poke your head down the side of the engine.  Connect a voltmeter between the temp wire and a solid ground.  An old analogue meter with a needle will be easier to follow than a digital type.

Observe the meter reading under the following conditions
Ign ON but not running
HT lead off the coil and engine cranking
Engine running (remember to refit HT lead)
The brief period just after the ign is switched off while running.

(The only reason to remove the HT lead is to allow enough time to get a cranking reading before the engine starts.)

My guess is that even when running there is power at the solenoid terminal, not enough to pull it in until the ign is powered off.  

Post the test readings and we can go from there.

[Jbird]

Thanks for the suggestion Peter. It's HEI so there is no ballast resistor or bypass wire, the back feed has to be through the ignition switch. I was going to use a diode but enjenjos "idiot" light bulb rang a memory bell. I wired the idiot light in series in the exciter wire right at the rear of the alternator. It'll be a conversion piece at the local car shows.

I've repaired cars that wouldn't shut off while the cooling fan or A/C fan was running, but this is the first time I had one zing the starter.

Jbird

[EMSjunkie]

Vance, I'll give you a bit of technical advice. Steer clear of enjenjos' place when lawn mowin season starts

Jbird

I have seen the News footage, not pretty  :oops:    


Vance