Re: '48 Electrical System Polarity

Posted by HH56 On 2011/4/17 17:46:28

Did you hear the solenoid try to energize. Should be a fairly loud heavy click or clunk. The light is on because 4 also is powering the lamp on one side and it's circuit is complete because the solenoid has not energized to the point of opening a contact at term 7 at solenoid. It is supposed to light telling the driver to lift his foot off accelerator so solenoid can move. As soon as it moves, light goes out. No movement could be because the pawl is not in a position to let it complete the stroke or, if you did not hear it trying to energize, the contact inside the solenoid that cuts out the pull in coil when stroke is complete or the pull in coil itself is open. I suspect one or the other because of the 6v vs 4.5. Term 3 is at a lower voltage because the hold in coil is drawing some current and putting a load on it's 6v supply. It is not strong enough to bring the solenoid in alone. The pull in coil doesn't act like it is in the circuit as there seems to be no current draw. The contact does pit and burn & is a periodic service item, the pull in coil could be burned open if the solenoid sat energized for an excessive time without being able to move so the contact could disconnect it.

I think it would be time to verify the wiring and connections are good to the solenoid and solenoid itself. You won't be able to check the voltage at solenoid from the top but If the lamp is on a separate wire at relay terminal 4, you can remove the wires going to solenoid off relay 3 and 4 and make a continuity check using the wires. If lamp is spliced into the loom and only one wire is connected on 4, then you will get a false reading and have to go under to disconnect the wires at solenoid and make the checks directly on the solenoid. It would really be best to do all these checks from below so you can hear the solenoid and also measure the voltage.

Anyway, checking the wire off relay 3 to ground, you should have a short or very low ohm reading. Off wire 4 to ground should be a short. If you have to go under, Look also for a group of black plastic connectors a few feet from the OD connecting that short wiring cable to rest of engine loom. If those are present (may have been removed), they were a source of problems.

If the OD knob is all the way in and lockout switch is open, that could be due to a bad switch or wear on the plunger. Ozstatman just detailed a similar situation with the plunger a few weeks ago and what they did as a quick fix in his running commentary Wades Workshop.