Electrical issue with brake lights
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New User
Joined: Aug 2005
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From: Denver
Electrical issue with brake lights
I have an interesting issue with my brake lights that I would like a little input on from you guys and gals.
I have a 1978 F250 4WD that I am getting up and running. While checking lights and bulbs I noticed I didn't have a passenger side brake light (Driver's side is fine).
- Checked the bulb - it's fine
- Checked the current with a circuit tester - no current
- Checked the turn signal - works. (both turn signal and brake light share the same wire, so wire appears to be alright since turn signal works.
- Rechecked brake light again - no power
- Pierced the green wire with a tester light and I get pulsing turn signal only.
- Checked wiring plug and I'm getting electricity for all except passenger side brake light
So what I know - electricity is passing through the wire because I am getting turn signal - just no brake signal.
After following the "282 Gr" brake light wire on a wiring schematic, I find it runs to the turn signal switch. The switch does not cancel so I was planning on changing it anyway, but is my thinking correct - can my brake light issue be related to the turn signal switch?
I have a 1978 F250 4WD that I am getting up and running. While checking lights and bulbs I noticed I didn't have a passenger side brake light (Driver's side is fine).
- Checked the bulb - it's fine
- Checked the current with a circuit tester - no current
- Checked the turn signal - works. (both turn signal and brake light share the same wire, so wire appears to be alright since turn signal works.
- Rechecked brake light again - no power
- Pierced the green wire with a tester light and I get pulsing turn signal only.
- Checked wiring plug and I'm getting electricity for all except passenger side brake light
So what I know - electricity is passing through the wire because I am getting turn signal - just no brake signal.
After following the "282 Gr" brake light wire on a wiring schematic, I find it runs to the turn signal switch. The switch does not cancel so I was planning on changing it anyway, but is my thinking correct - can my brake light issue be related to the turn signal switch?
Elder User
Joined: Sep 2014
Posts: 862
Likes: 7
From: like subarctic, brrr man!
Yes it can be.
After the Brake light switch (On the Pedal) it's first stop is in the turn signal/hazard switch(es) assemby. From there it separates into Left/Right Turns and Stop, Kinda like a trailer plug setup.
See if you get volts at the under column Connector? Ohm from there to the back if you hafta.
After the Brake light switch (On the Pedal) it's first stop is in the turn signal/hazard switch(es) assemby. From there it separates into Left/Right Turns and Stop, Kinda like a trailer plug setup.
See if you get volts at the under column Connector? Ohm from there to the back if you hafta.
Last edited by ZarK-eh; Jul 14, 2016 at 09:37 PM. Reason: left turns, wat?
Fleet Mechanic
Joined: Sep 2014
Posts: 1,626
Likes: 78
From: NE Texas
at the risk of beating a dead horse - also check all of your grounds. I had exactly the same symptoms a few months back and discovered that while the ground wire was great the actual socket-to-ground-wire connection was crap... in the front turn signal socket. Replaced that socket for a few bucks and suddenly my REAR signals and brake lights started working right. Based on my limited experience over the last few decades, I would say that probably 90+% of what I originally thought were switch problems on old cars turned out to be ground problems.
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,188
Likes: 5,792
From: S/W Missouri, Polk county
2 of the best reads on this problem. https://www.ford-trucks.com/forums/1...ml#post1812190
Turn and Stop Lamp Diagnosis for 70's Ford Pickup - Ford-Trucks.com
Turn and Stop Lamp Diagnosis for 70's Ford Pickup - Ford-Trucks.com
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