The Stovebolt Site Forums The Shop Area The Electrical Bay Wires melted

Have been having problems with my push button start on the dash. Replaced the button but then I wasn't getting contact to the starter. Went through all wires on starter and found one where the connector came off the wire. Replaced connector and all seemed fine. Today I tried to start and saw a spark. Checked under dash and didn't see any wires touching or anything wrong. Tried to start again and button got hot and the plastic fried on wire. What could have caused this? This is a 1951 GMC 150-22, (3/4 ton) with a 235 straight 6. Going to replace these two wires to the starter with 14 gauge, but wonder what I need to check so this doesn't happen again. Wondering if my button is fried also? Also, I don't have a ground strap from the engine to body. Should I have one?

Sounds like you have an electric solenoid type starter. Is the dash switch and wires rated for this application? If so, then you may have a bad solenoid. Since this type of switch just uses a hot wire loop from the battery positive (maybe indirectly in your case) to the solenoid, cab grounding is not in the picture.
Carl

Is there a way I can check the solenoid? The wires and switch have been on here since the engine was swapped out nearly 40 years ago. Originally had a 228.
Thank you Carl!

The surge current while the solenoid "pull in" winding is engaging the drive gear into the flywheel is over 50 amps. As the gear engages and the armature begins turning the "hold in" winding takes over at about 8-10 amps and the pull-in current is disabled. You need a push button heavy enough to carry the initial surge. I recommend a marine-rated push switch with at least a 40 amp capacity- - - -more if possible, and 12 gauge or bigger wires.
Jerry

I have been fighting a start problem for several days on my hot rod plus my IR shop compressor blew a reed valve plate gasket (good luck getting parts or help for your IR shop compressors from Ingersol-Rand).
Jerry, I have taken a number of solenoids apart over the years and have never seen a "hold in winding" in one. All I have seen is the coil which acts as an electromagnet to pull the 'cup' or piston into a position to throw the starter gear into the ring gear and the high current switch in the back part of the solenoid. This switch is nothing more than a copper washer that moves away from the ring gear when the electromagnet is energized and contacts two copper buttons mounted in the plastic housing of the solenoid completing the high current path for the starter. Where is this "hold in" winding?

Take the solenoid cover off and look closely at the wires from the "start" terminal post. (the small one marked "S" on the cover. There are two wires attached to it, one much smaller than the other. The bigger of the two wires grounds through the big terminal that attaches to the motor lead in the starter. That's the pull-in winding. As soon as the contact disc makes connection to start turning the motor, there's equal voltage on both ends of that winding and current flow stops. The hold-in winding grounds to the solenoid case and keeps the plunger engaged as long as the switch is in the "start" position. It has hundreds of turns of fine wire and draws much less current. You can check the resistance of both windings with an ohmmeter, depending on where you attach the leads.
Jerry

Thanks Jerry. Will take a look tomorrow.

Well, I'll be! Will have to look closer. Thanks

Overcoming that starter drive spring to get the solenoid to engage the gear takes a heavy current. Once the spring is overcome and the starter begins turning, much less force is necessary to keep it engaged. That's why the pull-in gets disabled. Small, flimsy push buttons can't handle the initial current surge.
Jerry

Finally got around to replacing the two wires. Only one wire melted, the one going to the "s" connection. Connected the push button back and cranking fine. No melting. Not sure what happened. But now I'm not getting gas into the carb. Will move to a new forum. Always something!