Trailer Wiring Weirdness
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Unplug the PCM then if the pulling the relay does not effect it I would say bad PCM.
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I have to walk away from this for now. It has taken too much of my time and I am behind on other projects. I wish I never noticed this.
If I take it up again, I'll post. Thanks again,subford, for all the time that you put into this.
If I take it up again, I'll post. Thanks again,subford, for all the time that you put into this.
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Solution: barnyum17 was correct in post 18. This is "normal" for some vehicles. I consider it a factory defect.
Search "Pulse Preventer" and "cequent 20501".
You remember when I said that the factory wiring was not altered and there needs to be a diode somewhere?
Tow Ready 20501 Pulse Preventer (Tekonsha 2180-S) | American RV Company
Tekonsha - Pulse Preventer Click on "Install Instructions".
Search "Pulse Preventer" and "cequent 20501".
You remember when I said that the factory wiring was not altered and there needs to be a diode somewhere?
Tow Ready 20501 Pulse Preventer (Tekonsha 2180-S) | American RV Company
Tekonsha - Pulse Preventer Click on "Install Instructions".
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
That "Pulse Preventer" will not help you.
As per the instructions it is for a 1989 -1991 Ford truck and you have a 1993.
The Multi-Function Switch is wired different in the 1989-1991 trucks and the Hazard switch does not disconnect the brake lamp circuit from the stop light switch.
In 1992 and newer OBS truck the Multi-Function Switch disconnects the brake lamp circuit from the stop light switch.
As per the instructions it is for a 1989 -1991 Ford truck and you have a 1993.
The Multi-Function Switch is wired different in the 1989-1991 trucks and the Hazard switch does not disconnect the brake lamp circuit from the stop light switch.
In 1992 and newer OBS truck the Multi-Function Switch disconnects the brake lamp circuit from the stop light switch.
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Crap
I saw in the diagrams that you sent that it does disconnect the brake lamps. I tested this and id works. I also don't see any connection between 361 (IIRC) from relay 1 and the brake light/ flasher systems but there is.
My nephew tells me to forget about it. Good it is almost a challenge to fix it.
subford, from what you know should it be working like it is or should the hazards have no effect on the trailer brake power?
I saw in the diagrams that you sent that it does disconnect the brake lamps. I tested this and id works. I also don't see any connection between 361 (IIRC) from relay 1 and the brake light/ flasher systems but there is.
My nephew tells me to forget about it. Good it is almost a challenge to fix it.
subford, from what you know should it be working like it is or should the hazards have no effect on the trailer brake power?
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
The hazards should have no effect on the trailer brake power.
I just took two Multi-function Switches apart and cleaned them so they work right and both had no connection from the brake light switch contacts to the lamp circuits contacts when the hazards was in the on position. But they did have connection with the hazards off. I took them apart because the were open to tests and had green corrosion on the contacts before I cleaned them.
I just took two Multi-function Switches apart and cleaned them so they work right and both had no connection from the brake light switch contacts to the lamp circuits contacts when the hazards was in the on position. But they did have connection with the hazards off. I took them apart because the were open to tests and had green corrosion on the contacts before I cleaned them.
Fleet Owner
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From: Easton,Ks
After I cleaned the contact surface with scotch brite pads then I used dielectric grease.
Then wiped the grease off and put the switch back to together.
Tried contact cleaner first but had no luck cleaning the contact surface.
Then wiped the grease off and put the switch back to together.
Tried contact cleaner first but had no luck cleaning the contact surface.
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I have never had success with contact cleaner except on potentiometers in stereos. Rubbing alcohol works better. Apply it with a syringe and a small diameter needle.
I don't get it: you put the grease on then wiped it off? You ever loose a spring taking things apart?
I don't get it: you put the grease on then wiped it off? You ever loose a spring taking things apart?
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
When I wiped it off it left a small film on the contact surface.
No but one spring jumped out when I dropped a part of the switch and I could not come up with where it came from so I took the second switch apart to find out where it went.
/
No but one spring jumped out when I dropped a part of the switch and I could not come up with where it came from so I took the second switch apart to find out where it went.
/
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I have a theory on what happens to small parts that disappear. There are miniature worm holes all around us. The part hits our end of the worm hole and is whisked off to somewhere else. Do you ever get a sudden sharp pain somewhere on your body that you can't explain and it just as suddenly goes away? That is because your body just made contact with the worm hole.
There is someone somewhere that is finding all these little parts showing up and says where the hell is all this stuff coming from?
There is someone somewhere that is finding all these little parts showing up and says where the hell is all this stuff coming from?
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Senior User
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I have a theory on what happens to small parts that disappear. There are miniature worm holes all around us. The part hits our end of the worm hole and is whisked off to somewhere else. Do you ever get a sudden sharp pain somewhere on your body that you can't explain and it just as suddenly goes away? That is because your body just made contact with the worm hole.
There is someone somewhere that is finding all these little parts showing up and says where the hell is all this stuff coming from?
There is someone somewhere that is finding all these little parts showing up and says where the hell is all this stuff coming from?
Fleet Mechanic
Joined: Aug 2011
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By any chance is your 3rd high point brake light burnt out? If that bulb is burnt out your brake controller will get turned on by the pcm as there is no load on the brake wire when the hazards are turned on.
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Mar 6, 2019 09:51 AM