Recently picked up a project car. Has a 59ab flathead converted to 12 volts. In looking at the solenoid it appears the positive and negative cables are on the wrong sides from what I have seen. Seems to run and start fine, is this a concern or doesn't it matter? Wiring not my strong suit. Thanks much for any and all information.
Solenoid wiring
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Roger/Sacramento
Senior Member
I don't follow what you mean by negative cable. A +cable goes from the battery to either side and a cable goes from the other side to the starter. The solenoid mounting tabs should be grounded to the fire wall.
39portlander
Well-known member
I'm an HVAC service tech. 80% of our problems are electrical, I would say automotive is pretty close and electrical should be our strength.
Here are 3 great books to get you out of the shadows. The official 12 volt conversion guide by Randy Rundle, How to wire your street rod from start to finish by Jack Sweeden and Bill Sinclairs Thunder road electrical guide.
I would check out Ron Francis web site and get his latest wiring catalog, all kinds of good stuff there.
Here are 3 great books to get you out of the shadows. The official 12 volt conversion guide by Randy Rundle, How to wire your street rod from start to finish by Jack Sweeden and Bill Sinclairs Thunder road electrical guide.
I would check out Ron Francis web site and get his latest wiring catalog, all kinds of good stuff there.
V8COOPMAN
Well-known member
Gotta ask.......from what you've seen, compared to WHAT? Do you mean: Compared to similar cars that are still 6v, POS Ground?
Without details of your particular situation, MOST folks that upgrade to 12v on an older car do so in addition to changing the GROUND(S) to NEG, from POS Ground on the original 6v arrangement. If your situation is as above (changed from 6v, POS GND to 12v, NEG GND), then the POS and NEG cables will most-likely go to the OPPOSITE-side poles than originally routed on the solenoid. The solenoid ITSELF (while it is moving huge ampere load to the starter) doesn't really care which poles are hooked-up to POS or GND...that part (function) of the solenoid only acts as a switch, to flow current (amperes) to the starter motor. The part of the solenoid that DOES matter is the SMALL pole, with the small wire that usually needs to be GROUNDED (via start switch) to energize the solenoid. It needs to be GROUNDED the OPPOSITE polarity of whatever (POS or NEG) polarity directly feeds solenoid (to starter) from BATT.....whew! Sorry for the long-winded BS. DD
donald1950
Senior Member
the Echlin ST56 12v solenoid does in fact wire to the oposite sides of the solonoid from the 6v unit. ST53 is the 6v unit with push button and ST62 solonoid is the 6v unit w/o the push button . both only have 3 terminals. ST81 is 12v and has 4 terminals, one for the starter button and one for the "I" terminal to provide momentary 12v to the coil for "12 volt starting". all 3 use a ground supplied from the starter button to energize the solonoid coil from power supplied from the battery.... if you go to a NAPA store and look in the Echlin Ignition parts book you will see how they work...... don
V8COOPMAN
Well-known member
Either side is OK. Don't want to complicate your life but if the car was also converted to a key start the small post on the solenoid puts 12 volts on the solenoid. if the push button is retained it grounds the solenoid to activate the starter.
Like I tried to allude to in my above reply, we don't know WHAT was changed/modified in his situation without more-complete details of the components used. DD
Thanks guys. To clear things up, the solenoids I have seen have had the positive battery cable attached to the post on the S side of the solenoid. Mine is opposite. I do know how the solenoid works and didn't think it would make a difference, but was wondering if I was missing some. Thanks again
rotorwrench
Well-known member
Three terminal solenoids are the ones to be concerned about. As Donald1950 mentioned, they can be wired incorrectly if a person doesn't know how their internal circuit is designed to work. The old Ford OEM solenoids had an internal circuit from one of the large terminals (battery post connection) to the energizing coil inside that is not visible. The little terminal is then connected to the dash mounted start button and that button grounds the circuit to the dashboard to close the circuit & energize the coil for starting. An S terminal should indicate "Starter" if marking a specific terminal to connect to it. The other large terminal should be labeled B or Bat.