quick wiring question
Elder User
Joined: Jan 2008
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From: N.W. Mo.
The positive battery cable connects to the solenoid and is always hot.
The large wire on the alternator is always hot. It comes from the solenoid terminal with the battery cable on it.
The coil wire should only have current to it when the ign switch is on.
The large wire on the alternator is always hot. It comes from the solenoid terminal with the battery cable on it.
The coil wire should only have current to it when the ign switch is on.
Elder User
Joined: Jan 2008
Posts: 658
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From: N.W. Mo.
Is this a problem that has occured on a vehicle that was running ok before.
If so probably a bad ign switch, solenoid, or a short in the wiring as highboy said. Disconnect both (if there are two) small wires at the solenoid and then check it. If that doesn't change it un plug the wires from the ign switch.
If this is not a vehicle that has been running it may just be wired wrong somewhere.
If so probably a bad ign switch, solenoid, or a short in the wiring as highboy said. Disconnect both (if there are two) small wires at the solenoid and then check it. If that doesn't change it un plug the wires from the ign switch.
If this is not a vehicle that has been running it may just be wired wrong somewhere.
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Posting Guru
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From: Revelstoke B.C.
Is this a problem that has occured on a vehicle that was running ok before.
If so probably a bad ign switch, solenoid, or a short in the wiring as highboy said. Disconnect both (if there are two) small wires at the solenoid and then check it. If that doesn't change it un plug the wires from the ign switch.
If this is not a vehicle that has been running it may just be wired wrong somewhere.
If so probably a bad ign switch, solenoid, or a short in the wiring as highboy said. Disconnect both (if there are two) small wires at the solenoid and then check it. If that doesn't change it un plug the wires from the ign switch.
If this is not a vehicle that has been running it may just be wired wrong somewhere.
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MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
In my mind I can't see how a bad solenoid would cause the coil to be hot because the only circuit the solenoid closes is the starter. When the solenoid goes bad, one of two things happens: you turn the key and nothing happens, or you crank the motor and the motor won't stop cranking once you let off the key (really scary!) The only problem I can see the solenoid causing is if somehow the 'I' terminal is shorting but that'd be pretty easy to check. Most likely someone has severely hacked the wiring, or the ignition switch is bad. If you find that someone actually wired it this way and this is the stock coil, you'll want to make sure it's powered through a resistive wire as well because if someone rewired it like this, they most likely messed that up as well. It's worth investigating.
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Two things:
First. solenoid went bad sending power constantly to the coil
Second. the circuit goes THRU the alternator so if the alternator is grounding out it WILL send power to the coil as well.
Either way, if you have power to the coil with the key off, that means you have power to the coil 24/7, not good for the longevity of the coil.
Josh
First. solenoid went bad sending power constantly to the coil
Second. the circuit goes THRU the alternator so if the alternator is grounding out it WILL send power to the coil as well.
Either way, if you have power to the coil with the key off, that means you have power to the coil 24/7, not good for the longevity of the coil.
Josh
Cargo Master
Joined: Sep 2003
Posts: 2,110
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From: southwest pa
dont quote me on this 100%, but when i went thru the wiring on the 75, there was one wire that fed the coil. i think there are 3 wires in that loom.....coil, volt meter, and oil pressure.......i think. the truck isnt here for me to look at. i can't remember where the coil wire comes from, but im pretty sure it came from the key. it's been 3 years. do like was said above, unplug the key and see if its hot. theres only going to be two places this could get screwed up. ignition or solenoid.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
Maybe I'm just not seeing it - could someone explain how the solenoid going bad could affect the coil? The only thing the solenoid does is close the starter circuit when there is voltage on the 'S' post. I'm not saying anyone is wrong, I'm asking for clarification so I know in the future.
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From: Revelstoke B.C.
I seem to have fixed the problem.
Forgive me,I don't remember exactly remember which wire was for what,as far as labels on the alternator are concerned.With that being said,I have three of these old truck's
-'76 Highboy(daily driver)
-'77 Highboy(part's truck)
-'79 F150 2 wdr. Flareside(this is the problem topic truck)
All three truck's have the same orange wire running from the voltage regultor to the alternator.This wire was hot on the '79 with the ignition off.I swapped the regulator out of the '77 and everything seem's to be working normal.
Forgive me,I don't remember exactly remember which wire was for what,as far as labels on the alternator are concerned.With that being said,I have three of these old truck's
-'76 Highboy(daily driver)
-'77 Highboy(part's truck)
-'79 F150 2 wdr. Flareside(this is the problem topic truck)
All three truck's have the same orange wire running from the voltage regultor to the alternator.This wire was hot on the '79 with the ignition off.I swapped the regulator out of the '77 and everything seem's to be working normal.
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