The Stovebolt Site Forums The Shop Area The Electrical Bay I'm making things worse, not better--Update 11/24

My '48 GMC 1Ton had been converted to 12V and negative (-) ground, had a new wiring harness installed before my purchase and still uses the 6V starter with its original starter switch. The wire from the ignition switch was run directly to the positive (+) terminal on the coil without being run through the ballast resistor.
My reading here on the electrical forum convinced me to use a ballast resistor and upgrade the starter switch to the type that has an extra terminal on the switch to provide 12V power to the coil during cranking.
I mounted the new switch---I think I created a new yoga position, "prostrate man with dangling arm"---and wired it up. Upon reconnecting the battery I felt the coil heating up even though the ignition switch was in the off position. I have 12V at the battery connection to the starter and 12V at the side terminal and that can't be right. Bad switch?
I disconnected the wire from the starter to the coil and tried to crank the engine but nothing happened when I pressed the stomp button except that I could smell something getting hot!
2nd vote for bad switch?
Anyway, looking for opinions before I make a stink with the vendor and return the switch. Thanks for your help! Jim

***Update 11/24*** Things are better now! The starter switch was bad due to poor assembly. The lug for the battery cable was touching the contact for the side terminal on the underside of the switch all the time instead of just when the stomp starter button was being pressed. I adjusted the fit and everything works correctly. The engine didn't want to turn over because the starter was hung up on the flywheel. A funny sight watching my 125 lbs. rocking my dually flatbed back and forth like I was stuck in a snowbank. Old skills come in handy every now and then.
All this trouble could have been avoided if I had tested the new switch before I installed it. Lesson learned! And now I can change out a starter switch in about 5 minutes, considerably faster than the first time I did it. Jim

I would use my multi-meter to check the function of the switch before calling the vendor. Pull the switch and check it on the bench.

(hope the switch is OK. Vendors usually say electrical parts are non-returnable)

Eureka Jim,

You made mention of no ballast resistor. If a 12 volt coil was installed at the time of 6V to 12V conversion, it has an internal resistor. If it were me, I would get a new 12volt coil, get rid of the wire from the starter to coil, test the new ignition switch to make sure it is good, and simply run a wire from + on the coil, to the post on the switch that is hot when it is in the run position. Just my 2 cents, simple is better.

Jon

"My reading here on the electrical forum convinced me to use a ballast resistor and upgrade the starter switch to the type that has an extra terminal on the switch to provide 12V power to the coil during cranking. "

Jim,

Did you add the ballast resistor and a foot-pedal starter switch with a side terminal? Let us know what wire goes where in that set-up.

Jim, it sounds as though you are concerned that the side terminal of the new switch is always hot and is not turning off. Easy to test without pulling anything by using a test light.

With the ignition switch off, touch the test light probe to the side terminal without stomping on the starter. It should not light up. If it does, you have a bad switch or you are getting current from the ballast resistor. To test which one, disconnect the wire from the positive terminal on the coil to the ballast resistor and retest the side terminal. If the test light no longer turns on, the problem is the starter switch. If it turns on, drop down two paragraphs to ballast resistor check.

Still with the coil to ballast wire disconnected, touch the probe to the side terminal when someone stomps on the starter. It should light up. As soon as the stomp starter is disengaged, the light should turn off. If this doesn't happen, the starter switch is bad.

If all is good with the above, next thing I would try is a similar test at the ballast resistor. Put the probe on the terminal that connects to the ignition switch. With the switch off, the light should not turn on. With the switch on, the light should turn on. If the light turns on when the switch is turned off, either the switch is bad or the wiring is incorrect because an unswitched wire is attached to the input terminal on the ballast resistor.

Matt

Thanks everyone. I didn't think to bench test the new switch before installing it. I will next time! The wiring is straightforward, switched power from the ignition switch to the resistor, single wire from the resistor to the positive post on the coil. I installed a single wire from the side terminal of the new starter switch to the positive side of the coil.

When I got the truck there was a ballast resistor that had been bypassed. The coil, though working, had a deformed top and was leaking. I bought a new Delco coil and the new ballast resistor to match it. I don't know if the new coil is internally ballasted, so that's something I'll have to find out. With the ignition switch in the off position there is no voltage to the resistor but there is power present at the side terminal of the new starter switch. My understanding is that the side terminal is supposed to provide a full 12 volts to the coil only while the starter is engaged. Right now my coil is getting power and heating up even when the switch is off.

In a effort to get the truck started I disconnected the wire from the side terminal to the coil, bypassed the resistor and wired the switched power directly to the positive post on the coil, effectively restoring the original set up that was working with the old coil. I pushed on the stomp starter and the starter didn't turn, though I could smell something getting hot. So there may also be a problem with something other than the new switch. I can put the old starter switch back on but I'm not looking forward to that job with much enthusiasm!

That was enough for me for one day!

I think there may be some incorrect info in this Q&A. I believe coils may be purchased with and without an internal resistor. The ones I’ve seen are marked as having an internal resistor. I personally choose the ‘without’ one as I want the full 12 volts at startup.

The new coil is an AC Delco, part # U505 and it does require a ballast resistor.

The starter should spin whether or not the side terminal is connected. With the wire to the coil + disconnected, there should be NO voltage on the side terminal unless the foot pedal is depressed. Then it should have battery voltage. It sounds like you got a bum switch, something that's not uncommon, given where they're probably being made these days! It's also possible to displace the components of a good switch by putting too much torque on the big stud nut while attaching the battery cable.
Jerry

How is the side terminal on the solenoid used? I saw one for sale on one of the parts vendors websites but there was no explanation of what it did or how it should be wired.

Hello, Paul,

A lead from that side terminal goes to the "input" lead on the coil.

When the ignition is turned on, and then the starter foot-pedal is pressed, that lead is "hot" (full 12v), giving full 12v to the coil.

When, the foot-pedal is released (and the ignition switch is still on), the hot-lead from the ignition goes through a ballast resistor and then to the coil. The ballast resistor reduces the voltage to the coil (to approximately 8-9 volts). This lower "driving/operating" voltage does not burn the points. If 12v is always "fed" through the points, the points would "burn out".

Do not ask why (it is a historical/electrical oddity - on all early 12v GM vehicles).

A "hotter spark" for starting and a "lower/cooler spark" for driving.

Oh, yeah, there were/are coils with internal "ballast resistance" (coils for 12v VW bugs, for example). The use of this type of coil complicates the situation.

It's actually "the same spark" in both situations. When the starter is operating (particularly in very cold or very hot conditions) the load of the starter drops the battery voltage to approximately 9-9.5 volts. With the engine running and the generator/alternator charging, the "battery" voltage is actually the voltage produced by the charging system- - - - -14.5 volts or so. A 5 volt difference in what is applied to the the primary coil winding would create vastly different current flow across the points. The simple fix is to create a coil winding that will produce a hot spark at the lowest expected voltage, and protect the points with a resistor to reduce the current flow when the voltage is at its high limit. The bypass switch allow full (but low) battery voltage to be applied to the coil during cranking.

There's nothing exotic about it- - - -just good engineering to assure quick starts from good spark plug voltage when the battery is under load, and protect the points the rest of the time.
Jerry

I have a Pertronix ignition to install that I understand does not use the ballast resistor. Will it want the side terminal connection?

Do yourself a favor and leave the Pertronix in the box, or carry a spare distributor with points to swap in when the thing takes a dump in the middle of nowhere!
Jerry

Two Qs:

1. Is the side terminal needed withe the Pertronix? How is it wired?

2. Why don't you like the Pertronix units? At the urging of a pal I installed a 6v pos ground unit in my 1939 Cadillac and was very happy with the results. I know that is not a great deal of experience but it was a good one and among the few folks I know in the hot rod world they ALL like these units. I had thought I was getting away from the constant issues with points & condensers.

Those who don’t like the Pertronix system cite expensive parts if something breaks. You can’t just go down to your local FLAPS and get what you need to fix it. Points, condensers, rotors and caps are readily available.🛠

Right on Jerry!
About 25 years ago (Pertronix was new) I took the family down to the ocean (200 miles) to a big car show in my 62 Impala. It was fitted with a "Hall" effect type pickup. Kids were all little then. We get almost there and the engine dies. No spark! As luck would have it, there was a old type general store within walking distance, we were out in the sticks. I was thinking I was screwed, it was getting dark too. I walked into this place and it looked like the floor hadn't been mopped in a decade. I asked this 90 year old guy and said "I don't suppose you have a set of points and condenser for a small block chevy do ya"? He said he had everything, I thought yeah right. He said go down that aisle and look up on one of those pegs. I did and found a box of points and condenser hanging there. It had been there since Christ was a child. Lucky, I always carried tools and some bits of wire and MacGyver'd it back together. Moral of the story, if you are going to run a Pertronix, keep a spare set of points and a condenser in the glove box. Pertronix is a good company though, they sent me a new ignition.
Steve

Is the Pertonix something that frequently fails? My experience is not extensive but it has all been positive. My experience with points & condensers IS extensive and mixed at best. It SEEMS to me that in recent decades new condensers are not as good as they used to be. I have had new ones in the box fail or act strange. In my 1920s Hudsons I have very old condensers that are still working fine. Were they really better in the old days or were we just used to dealing with the problems? New cars are dead reliable, my newest car, a 1999 Dodge has only stranded me once when the battery failed.

If the rap on the Pertronix is only that it COULD fail and they are not available at any FLAP store I'm prepared to take that risk and bring a spare Pertronix or points & condenser.

Early Pertronix had problems, cant say to as their reliability now though.

It seems the Pertronix is VERY susceptible to having a catastrophic meltdown if the ignition switch is left on for a few minutes without the engine running. The parts are also proprietary to that system, and aren't available readily at local parts stores. Points can burn under an "ignition on- - -engine off" situation- - - -or not- - - -depending on whether the engine happens to stop with the points open or closed. It's almost a guaranteed disaster with a Pertronix. If you want an electronic ignition system, the OEM General Motors HEI distributor for a 250 6 cylinder is almost a drop-in fit, and parts for it are available everywhere.
Jerry

Thanks Jerry, the GM system will be worth a look.

I updated the original thread with a success story as an extension of the thread. Probably should have put it here as a new reply.