Starter Solenoid Burned Out / Constant 12 volts on "S" Post

ESolorzano

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May 30, 2022
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Hey everyone

Start: Car was running fine, I decided to change out the engine wiring harness (it was looking a little tired). Now I have a number of issues.

1. Solenoid: I have a constant 12 volts on the solenoid "S" post, this is true even when the key is not inserted. I believe that I should only have 12 volts on the "S" post at crank, 0 volts after that.
2. Solenoid: The solenoid is always active, so I removed the positive cable to the battery, any time it is attached the starter attempts to start the engine. Note the key is NOT inserted.
3. Solenoid: With the battery disconnected I turned my meter to ohms and found that the solenoid is shorted; hence the starter is always attempting to start the motor.
4. Ignition Switch: Purchased and installed a new ignition switch.

This is what I think I need to do
1. Replace the solenoid
2. Reconnect the positive side of the battery

My problem is basically that I believe that I will burn out the new solenoid if I don't first fix the 12 volts from the ignition.

Does anyone have any idea why I have 12 volts at the solenoid "S" post?
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Do you still have power at the 'S' wire with key off with the new ignition switch? (Not key switch)
Yes I think the solenoid needs replacing, just my opinion in general, you don't say year/make/model vehicle you have.
 
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ESolorzano

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May 30, 2022
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It's a 1968 Mustang. You are correct the solenoid needs to be replaced but it will burn out again if the 12 volt issue is not resolved first. I really need to find out why that is happening.
 

7991LXnSHO

wanna catch the space herp
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Unplug the harness plug from the ignition switch and see if you still have 12v at the solenoid trigger wire. If you do, you have something wired wrong. If you do not, either the switch is bad or it was hooked up wrong.
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Just to clarify, the 67 mustang has the switch on the dash, pretty basic 2 or 3 wires if I recall, been a minute.
Actually a lot of minutes :doh:
 
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7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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Kearney, NE
Just to clarify, the 67 mustang has the switch on the dash, pretty basic 2 or 3 wires if I recall, been a minute.
Actually a lot of minutes :doh:
I'm picturing similar ignition switch on my 60's GM's, although I got to work on a 68 stang in high school. Then I got to drive test it when it was repaired. The main power wire terminal can get hot with the fan, lights and aftermarket radio on high, and a loose melted plug makes it easy to mix up wires
 
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ESolorzano

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May 30, 2022
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Thanks for the reply, I do not have this switch on the dash. As soon as possible (probably tomorrow) I will disconnect the ignition switch as proposed above. The main issue with that is that it is difficult to disconnect the ignition switch. Very poor Ford design.

I'll post results as soon as they are available.

Thanks again.
 

ESolorzano

Member
May 30, 2022
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Sorry for the error, I did not know you were referring to the ignition switch. Yes it is mounted on the dash.
I did some work below, In short I think I found a wire which is out of place on the ignition switch. I hope the below makes sense.

Problems
The "S" post has a constant 12volts even when the key is NOT inserted. This burns out the solenoid. Original Issue
Documentation: The documentation I have appears to be incorrect on a physical level in regards to the ignition pigtail.

Findings
1. I think I incorrectly wired the solenoid. Wire number 6 (Red w/blue stripe) should be connected and it is not.
2. Solenoid wire number 7 (Red w/white stripe) should not be connected and it is.

Test for tomorrow
A. Disconnect Red w/white stripe connection from ignition. See Ignition Switch Wire number 6 below.
1. Need to make sure that "S" post on the solenoid does not have 12 volts constant when the battery is connected.
2. Check if the Red w/blue stripe wire has 12 volts at crank. If yes, correct / splice into ignition switch.
3. Replace solenoid, do start test.
4. Post results

New Harness Colors
Note 1: Found out that the Original Harness has Black with Yellow Stripe at the solenoid, which maps to solid yellow on the ignition. Based on wiring diagram
Note 2: The new harness has Solid Yellow at the solenoid as noted below.

In regards to the number of wires there are 7 (ignition pigtail) wires, however maybe only 3 are relevant for starting. Not sure

Ignition Switch Wires and where possible documented via observation and the wiring diagram.
1. Solid Yellow - Goes to ignition switch
2. Solid Purple - Purple to one side of 7.5 amp fuse Based on wiring diagram
3. Solid Pink - Same terminal with Green w/red stripe.
3. Green w/red stripe - Same terminal with Solid Pink wire.
4. Black w/yellow stripe - Ground. (Not verified) Based on wiring diagram
5. Red w/blue stripe - Goes to the "S" post in the Starter solenoid. Based on wiring diagram Possible problem. This wire is not connected. easy to check.
6. Red w/white stripe - This wire is connect and I do not believe it should be.


Starter Relay Solenoid
1. Battery Neg to Solenoid Neg - Solid Yellow, Verified visually
2. Battery Neg to Solenoid Neg - Solid Black, Verified visually
3. Battery Neg to Solenoid Neg - Solid Red, Verified visually
4. Starter Relay Solenoid "S" Post to Red w/blue stripe (12 volts @ crank only) Currently this terminal has 12 volts constant, this is the problem.
5. Starter Relay Solenoid "I" Post to Solid Brown to coil (12 volts @ crank, lower voltage when engine is on)
6. Battery Pos to Solenoid Pos - To starter
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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polk county florida
Numbers 1-2-3, I have never seen a ground from the battery connected to a starter solenoid ever in my life working on Fords. Explain what you are calling a solenoid. You have three ground (negative) wires going to the solenoid and that does not make sense. Maybe a pic of this solenoid you are referring to.
 

ESolorzano

Member
May 30, 2022
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59
Missouri
Corrected documentation from above, I did this a 2:30 am last night. I can post a picture later if you think it's still needed?

Wondering if Starter Relay would be more correct?

Starter Relay Solenoid
1. Battery Pos to Solenoid Pos - Solid Yellow, Verified visually
2. Battery Pos to Solenoid Pos- Solid Black, Verified visually
3. Battery Pos to Solenoid Pos - Solid Red, Verified visually
4. Starter Relay Solenoid "S" Post to Red w/blue stripe (12 volts @ crank only) Currently this terminal has 12 volts constant, this is the problem.
5. Starter Relay Solenoid "I" Post to Solid Brown to coil (12 volts @ crank, lower voltage when engine is on)
6. Battery Pos to Solenoid Pos - To starter

Thanks for your post
 

ESolorzano

Member
May 30, 2022
14
2
13
59
Missouri
Ok all

So I ran through most of the test plan above. Here is the update

1. Disconnect Red w/white stripe connection from ignition switch pigtail.
2. Connected Red w/blue stripe to the ignition switch pigtail.
3. Meter Test - Verified that the Red w/blue stripe wire indeed provides 0volts to the "S" post until crank (or start) at which time 12volts is present.
4. New Start Relay installed, performed a start test which was successful.
Important: Verified that the "S" post on the Start Relay no longer contains 12volts after start.

I think I am good here but I still have more issues. I will open a new thread.

Please reply if you have any comments.
 
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