Need help with turn signal wiring. (1 Viewer)

Perryb24

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I bought a 77 FJ40 about 18 months ago and have been trying to wring out some wiring issues. Most issues have been resolved. but one that I just can't figure out is the turn signals. Hazard works fine but turn signals not so much. When I select either left or right the flasher clicks once or twice and the lights for that side will stay lit. I have checked the grounds and sense the Hazards work I feel they are good. Even grounded the lights directly to the neg terminal on the bat. I believe the problem might be a couple missing wires in the main harness that connects to the steering wheel harness but I peeled back about 10 inches of main harness wrapping and see no unused wires. Pics give a better picture of what I'm talking about.

This is my first post and apologize if it's too wordy.
Thanks
IMG_1906.jpeg
IMG_1916.jpeg
FJ40 Turn switch.jpg
 
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YODA 88 62

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I also add dielectric grease to prevent/slow corrosion. It will need to be reapplied in the future. Aluminum and steel corrode when exposed to the elements. All spots on the frame that are sanded to bare metal for a ground get the same dielectric treatment with zinc coated bolts.

In a perfect world, all the ground wires throughout the system would be connected together and ground out on multiple parts of the frame and body…like modern wire harnesses.

Also, consider adding an additional, larger gauge, ground cable from the frame to the motor near the starter and battery. You can’t have too many.
 

Perryb24

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Yeah in our case the aftermarket bulb measured ~3 ohms resistance, the OEM bulb that worked was .5 ohms
The bulb I used was actually an 1156 not 1157 as I stated earlier. The 1157 is a two filament bulb and the socket for the turn signal is for a single filament bulb.
 

dtm

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There are bulbs that look like an 1156 and have the same bayonet mount but have different wattage and may or may not have markings to indicate what they are. That was our issue, sounds like it was yours too. Measuring the resistance of the bulb is a good way to estimate bulb wattage if you don't have any other info to go on. We didn't do any math we just took relative readings of bulbs that worked and didn't work and used one with a similar resistance to the known working one. But the math works out too: hot resistance of an incandescent filament is about 10x the cold measurement. Watts is volts squared divided by resistance. Our working bulb had a cold ohm reading of .6, so hot would be around 6 ohms. 12v squared is 144. so 144/6 = ~24 watts, which matches the 1156.

Maybe an easier thing to say is "make sure you have the right bulbs".
 

Perryb24

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There are bulbs that look like an 1156 and have the same bayonet mount but have different wattage and may or may not have markings to indicate what they are. That was our issue, sounds like it was yours too. Measuring the resistance of the bulb is a good way to estimate bulb wattage if you don't have any other info to go on. We didn't do any math we just took relative readings of bulbs that worked and didn't work and used one with a similar resistance to the known working one. But the math works out too: hot resistance of an incandescent filament is about 10x the cold measurement. Watts is volts squared divided by resistance. Our working bulb had a cold ohm reading of .6, so hot would be around 6 ohms. 12v squared is 144. so 144/6 = ~24 watts, which matches the 1156.

Maybe an easier thing to say is "make sure you have the right bulbs".
That was some pretty nifty bulb troubleshooting. Way more than I did and yours was more scientific than mine for sure. By me wiring the brake light bulb, which is a higher wattage, to the turn signal circuit and getting them to work told me that I needed a bulb with more wattage in that socket. That's what led me to trying the 1156 and fortunately it worked. Once again, thanks for pointing me in that direction. I don't think I would have got there on my own.
 

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