I have searched through many threads on this topic and even read through coolermans web page (great stuff by the way) and seem to be having a similar problem but stightly different than most I have read. I have a 76/77 40. My problem is only with the blinkers everything else works fine. I have checked the switch and have continuity were I should when I should. I have 12V at the green with blue wire when the ignition is on but when you turn the switch for the blinkers on either side the voltage drops out completely. All other lights work perfectly (running, brakes, and even the hazards). I am assuming that I have a short to ground somewhere in the harness but was hoping that someone might have some advice as to something else that might be causing this problem before I go pulling the whole harness out. Thanks
blinker problems
- Thread starter 1sttime40
- Start date
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It is not a short; it is a bad connection somewhere upstream (toward the battery) from where you are measuring. What you are experience is a "voltage drop" across a resistor, where the resistor is a bad connection. Keep checking the voltage in the circuit back toward the battery (with the blinkers on) and when you find the point where the voltage jumps back up, the bad connection is between the last two measurement points.
- Thread starter
- #3
OK that makes sense, but since my initial post I checked for continuity from the green with blue to ground with the blinkers off and nothing. Once I turn the blinkers on, I get continuity from the green with blue to ground. I then disconnected the plug from the switch under the dash and checked continuity from the green with yellow and green with black to ground and have continuity through both. So could it still be a bad connection between the battery and the switch or between the switch and the blinkers and how are the hazards still working? Doesn't the hazard switch feed the power over to the blinker switch?
Check your blinker fluid level 
You could get fooled by checking for continuity as the resistance may only be a few ohms. Check for voltage with the switch on.
Some hints:
If both turn signals don't work, chances are it is up stream from the turn signal switch.
The hazards get power from a separate fuse that is hot with the key off.
If I had to guess, I would guess that the problem is the hazard switch because it is subject to wear and oxidation. It can be cleaned and repaired. Check for the voltage on the green/red stripe power feed for the turn signals at the hazard switch and if it has 12V with the blinkers on, and there is no voltage at the green/orange stripe wire at the switch, then the problem is inside the switch.
You need to be Houdini to get up under there to make the measurements, let alone remove the switch. You might try some of that spray type contact cleaner first.
You can find the circuit diagram here:
http://www.yankeetoys.org/documents/wiring_diagram_78_fj40.pdf
Some hints:
If both turn signals don't work, chances are it is up stream from the turn signal switch.
The hazards get power from a separate fuse that is hot with the key off.
If I had to guess, I would guess that the problem is the hazard switch because it is subject to wear and oxidation. It can be cleaned and repaired. Check for the voltage on the green/red stripe power feed for the turn signals at the hazard switch and if it has 12V with the blinkers on, and there is no voltage at the green/orange stripe wire at the switch, then the problem is inside the switch.
You need to be Houdini to get up under there to make the measurements, let alone remove the switch. You might try some of that spray type contact cleaner first.
You can find the circuit diagram here:
http://www.yankeetoys.org/documents/wiring_diagram_78_fj40.pdf
Coolerman
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Bypass the switch entirely by jumpering from the GL to the GY and then the GB. (With the key ON) If the lights now blink you know it's the switch.
Remember you WILL get continuity to ground when measuring from the GL to ground with power off, and the turn signal in either position! In effect you are measuring across the bulb element to ground. The reading will be a bit high due to the element resistance.
If you remove the bulb, you can measure from GL on the switch (with the signal switch in either position, and key OFF) to the proper bulb socket contact to make sure you have a good path.
Good luck!
Remember you WILL get continuity to ground when measuring from the GL to ground with power off, and the turn signal in either position! In effect you are measuring across the bulb element to ground. The reading will be a bit high due to the element resistance.
If you remove the bulb, you can measure from GL on the switch (with the signal switch in either position, and key OFF) to the proper bulb socket contact to make sure you have a good path.
Good luck!
- Thread starter
- #8
Wow you guys are good. Had 12V at green/red but only ~3V at green/orange. Removed hazard switch, cleaned contacts and viola now I have blinkers. It is still a little weaker on the right side so I am going to dissasemble all of my connectors, clean and add a little dielectric for protection.
