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Hey guys, I am having some trouble with the ignition system on my truck, and im not sure where it went wrong. the problem i am having is constant power to the ignition coil, this is in turn making my coil blow. Ive been through three coils so far and have at least narrowed it down to constant voltage being the problem. I am just having difficulty finding where the problem is. This is what i am running currently.
Stock Dizzy w/ Pertronix module
Stock Type coil (blew up my MSD blaster as well as my pertronix flamethrower)
Stock ignition switch
Stock Solenoid
Stock Resistor Wire (ballast resistor)
Recent 3G alternator upgrade (problem started after this upgrade)
I have constant voltage at the Brown wire on the solenoid (not sure if i should or not? Could be bad solenoid?). I removed the ignition switch and tumbler to rule that out as a problem, even with the switch/tumbler removed the coil still has voltage. Here is where it gets confusing for me.
When i remove the positive connection from the pertronix unit to the coil, the coil no longer has voltage. The pertronix unit is connected to both the positive and negative side of the coil, so this is clearly interrupting the circuit. Im just not sure why? Could the pertronix unit be bad? I am at a loss.
You may have found the problem.
There is a path to the coil on the "I" wire at the solenoid. It is energized on starting to bypass the drop in the ballast resistor. Once the switch is dropped from start to run the voltage on the solenoid terminals goes away.
Chinese solenoids are a constant problem here. They are junk that are often dead out of the box or fail soon afterward. Motorcraft stuff is still available. Not cheap but good.
How the "I" wire got honked when you put in the new alternator, we can't tell you. You will have to do voltage checks.
Let us know what you find.
You may have found the problem.
There is a path to the coil on the "I" wire at the solenoid. It is energized on starting to bypass the drop in the ballast resistor. Once the switch is dropped from start to run the voltage on the solenoid terminals goes away.
Chinese solenoids are a constant problem here. They are junk that are often dead out of the box or fail soon afterward. Motorcraft stuff is still available. Not cheap but good.
How the "I" wire got honked when you put in the new alternator, we can't tell you. You will have to do voltage checks.
Let us know what you find.
If i understand correctly here, you are saying when the motor is NOT running this SHOULD have 12V, but when running it should not be powered? This is like the 3rd solenoid ive had on this truck already haha.
You should have 12VDC at the 'I' solenoid terminal ONLY in START. In RUN there should be zero voltage at the 'I' terminal. Likewise when the engine is not running....zero voltage.
If yer coil states it needs a ballast resistor to function properly, check if the ballast resistor hasn't shorted/fried out - Key in RUN, engine OFF, you're looking for ~ 8-9VDC from the coil (+) to ground. 12VDC at a coil that needs a resistor wire will fry a coil in a New York minute....mebbe a Joisey minute....
You guys need to think about this a little more.
The "I" on solenoid will have lower volts back feeding from the + side of the coil when running and a full 12 volts when starting, no volts when off.
Now if the solinoid was bad sending power it the "I" lug the starter would also be engaged. You can try a new solenoid but I bet it will not fix it.
This started when the 3G alt was added.
Recheck all the wiring to make sure it is right.
If that checks out remove all wires from alt and see if you still have power at coil.
If not bad diodes in alt.
Dave - - - -
You guys need to think about this a little more.
The "I" on solenoid will have lower volts back feeding from the + side of the coil when running and a full 12 volts when starting, no volts when off.
Now if the solinoid was bad sending power it the "I" lug the starter would also be engaged. You can try a new solenoid but I bet it will not fix it.
This started when the 3G alt was added.
Recheck all the wiring to make sure it is right.
If that checks out remove all wires from alt and see if you still have power at coil.
If not bad diodes in alt.
Dave - - - -
I had the alternator texted before install and it tested perfect. when the truck is off the I terminal has constant power (when it shouldn't). I even took the ignition switch out and the solenoid still had constant power on the I terminal. the voltage at the I terminal is 11-12 volts when everything is off, i keep the battery disconnected otherwise it would fry the coil just sitting in the driveway. All the 3g wiring is right (just two wires to the positive side of solenoid and then the one other wire which i matched with the factory harness). The alternator charges the battery at about 14 volts when running, i dont think there is a problem there. Im thinking maybe the solenoid got messed up while i was trying to figure out the wiring before (it was a huge mess before) I will hopefully have time to swap the solenoid tonight.
Key at START supplies the solenoid "S" terminal; the solenoid "I" terminal then supplies the coil.
Key at RUN supplies the coil directly, through the resistor wire. Shouldn't have 12V on solenoid "S" terminal except while cranking, but you will measure something, although negligible, on the "I" terminal.
You can make the solenoid close yourself by jumping the battery terminal of the solenoid to the "S" terminal with a screwdriver, just be careful not to ground it out.
If a solenoid seems "stuck" closed, allowing voltage through, a coupla hard whacks (with the plastic end of a screwdriver, not a beater) will often free it up.
Key at START supplies the solenoid "S" terminal; the solenoid "I" terminal then supplies the coil.
Key at RUN supplies the coil directly, through the resistor wire. Shouldn't have 12V on solenoid "S" terminal except while cranking, but you will measure something, although negligible, on the "I" terminal.
You can make the solenoid close yourself by jumping the battery terminal of the solenoid to the "S" terminal with a screwdriver, just be careful not to ground it out.
If a solenoid seems "stuck" closed, allowing voltage through, a coupla hard whacks (with the plastic end of a screwdriver, not a beater) will often free it up.
I have a start button i can use to jump the terminals, i gave it a few heft swings sunday afternoon with the back of a screwdriver to no avail haha.
I had the alternator texted before install and it tested perfect. when the truck is off the I terminal has constant power (when it shouldn't). I even took the ignition switch out and the solenoid still had constant power on the I terminal. the voltage at the I terminal is 11-12 volts when everything is off, i keep the battery disconnected otherwise it would fry the coil just sitting in the driveway. All the 3g wiring is right (just two wires to the positive side of solenoid and then the one other wire which i matched with the factory harness). The alternator charges the battery at about 14 volts when running, i dont think there is a problem there. Im thinking maybe the solenoid got messed up while i was trying to figure out the wiring before (it was a huge mess before) I will hopefully have time to swap the solenoid tonight.
I bet they only checked to make sure it was putting out not if there was a short and back feeding when not spinning.
I posted how to check if it was the ALT back feeding in to the system, remove all wires and see if you still have volts.
Want to see if the solenoid is the cause? Easy remove the wire on the "I" lug of solenoid and see if you have power on the wire and then the solenoid. I bet you have it on the wire.
Now if you have not pulled the wires to the ALT do it and test the "I" wire for volts.
Want to see when the "I" lug gets volts. No wire on it and jump from batt. to "S" lug on solenoid and you will now et power on the "I" lug ONLY when the solenoid is pulled in.
Originally Posted by Filthy Beast
Key at START supplies the solenoid "S" terminal; the solenoid "I" terminal then supplies the coil.
Key at RUN supplies the coil directly, through the resistor wire. Shouldn't have 12V on solenoid "S" terminal except while cranking, but you will measure something, although negligible, on the "I" terminal.
You can make the solenoid close yourself by jumping the battery terminal of the solenoid to the "S" terminal with a screwdriver, just be careful not to ground it out.
If a solenoid seems "stuck" closed, allowing voltage through, a coupla hard whacks (with the plastic end of a screwdriver, not a beater) will often free it up.
Thank you that is what I was trying to tell him.
He needs to do more testing to find just were the issue is and not just change out parts.
BTW I have seen ALT test ok, put out power, but back feed and keep motors run or a dash ALT light on.
And funny this all started after the ALT swap
Dave ----
Dave, aka FuzzFace2 - I have seen the 3g setup test out ok but make a mess of things if the vehicle is running and a battery cable disconnected.....shorts out the internal regulator and could cause the alternator to run full field.......
In the old days of pulling a batt cable to check out put of generator is a BIG NO NO with a ALT. and even more so with todays high out put ALT's for just what you said.
I still think the feed back is the ALT but we will have to see after has does more testing.
Dave ----
Yeupp...."Back in the day....hahaha" I've been guilty of yankin' a battery cable to check the GENERATOR......6v from '55 and earlier, 12v on '56 on up. But NEVER with a vehicle with an alternator.
I'm glad there are others like yourself that know it's a major faux pas to do that.
Yessuh, more troubleshooting is in order, since the "whack trick" didn't help free up the solenoid....
Yeupp...."Back in the day....hahaha" I've been guilty of yankin' a battery cable to check the GENERATOR......6v from '55 and earlier, 12v on '56 on up. But NEVER with a vehicle with an alternator.
I'm glad there are others like yourself that know it's a major faux pas to do that.
Yessuh, more troubleshooting is in order, since the "whack trick" didn't help free up the solenoid....
Some would say "showing our age" I like to say "showing our wisdom" LOL
Dave - - - -
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