UPDATE – 8.4.2016
ADMIN! Can you please move this update directly below my initial post so that it'll be easier to find the solution to my problem for future readers. Also...how do you put pictures in between text. I'm a little new at the posting on forums.
I spent the day troubleshooting and was able to unravel my mystery. It seems that I had a multitude of problems.
Problem 1: Speedometer is not working:
Solution 1: It seems that the speedometer mechanism in the gauge itself is broken. I’ll have to replace or repair the speedometer. Does anyone know where I can get the entire gauge? I’ve seen the gauge faces on LMC and other sites but they don’t seem to have the odometer.
Problem 2: Dash Lights were not working: None of the interior lights, dash lights, etc. were working. Headlights and highbeams work okay.
Solution 2: The headlight switch contacts are about shot and only intermittently control the interior lighting. I could clean up the contacts or replace the switch. The switch is old, poorly painted and hard to operate...I think I’ll just replace it.
Problem 3 / 4: The temperature and oil pressure gauges do not work: The voltmeter and fuel gauge work.
Solution 3 / 4: The hot and ground seem to be in working order via the meter. I haven’t fully traced out the signal wires yet but I’m sure I’ll find they are disconnected because the signal wires for the aftermarket gauges are mechanical and directly connected to the sensors themselves. I’ll reconnect the signal wires and replace the mechanical oil pressure sensor with the factory electric oil pressure sensor.
I did have one final question if anyone can help:
What is this switch? I believe it’s the transmission kick down switch but I’d like to confirm. If it’s not that, any ideas what it would be?
https://s32.postimg.org/yz5hfwuit/Unknown+Switch.jpg
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Troubleshooting Process:
I started at the end, because my common sense and all of the troubleshooting guides say not to but my curiosity of what wiring nightmares might be got the best of me. I would recommend however, always start simple before starting to take apart your truck!
I first had to figure out what the previous owner had done because my suspicion was that there would be some cut wires somewhere. I had (7) T-Taps to hunt down and this is what I started with:
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Not getting to deep in the weeds, I discovered that the T-Taps were for:
Radio Power 1
Radio Power 2
Sun Visor Light Power
Aftermarket Temperature/Oil Pressure Gauge Power
Aftermarket Tachometer Power 1
Aftermarket Tachometer Power 2 (Not sure why there’s 2 power wires yet. I never hooked one of these guys up before)
Aftermarket Voltmeter Power
Carburetor Electric Choke
I disconnected the radio because it was apparently wired by a spider! That will go back in later with proper care and routing.
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Now that the wiring is slightly cleaner, the dash cluster removed and some room to work, I can dig into the guts of this and look for my suspected cut wires. I found this switch disconnected and no idea what it was. It was time to start unraveling the 40yo mysteriously sticky, yet dry electrical tape!
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After tracing the wire from the fuse block to the dash cluster connector (Pin 13), it appears to be the Safety Belt Warning Switch connector. This switch didn’t run through anything else on the cluster, so I’ll leave it be for now and conclude that it is not the culprit for any of my current woes.
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Safety Belt Switch harness wiring
After the Safety Belt distraction, I found another unconnected wire! Surely this was the open I was looking for!
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Nope. It’s apparently the factory in-dash speaker. Another dead end.
At this point in time there was nothing else disconnected so I began by identifying the circuits on the Dash Cluster Connector. I have yet to find a wiring diagram that matches what I have, so I’ll have to do it the hard way. Here is my dash setup and the 18pin connector:
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Pins 1-9
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Pins 10-18
Getting everything identified was the longest part. The most important thing I learned was which pins were steady hot and ground. Everything else was either a signal/switched wire to ground/hot. Below is my trucks wiring.
*There is some wiring I didn’t trace out because it isn’t necessary at the moment. Additionally, anything labeled as coming from the fuse block is a relative guess. I traced the loom to the fuse block but did not see its final terminations.
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Troubleshooting Problem 1: Speedometer not working
I first tested the speedo cable at the transfer case. I turned it both directions with a drill and the gauge didn’t budge. After pulling the cluster out, I found the cable was disconnected but in seemingly good condition. I put the drill right to the gauge and spun the gauge up again. In both directions, the gauge did not move. It would appear that I need to buy a new speedometer.
Troubleshooting Problem 2: Dash Lights were not working
Now that I identified which pin was responsible for the dash lights, I just had to trace the wire to its switch and find out why power wasn’t getting through. I thought these went to the headlight switch but because it wasn’t working I doubted myself. I went to the switch anyway and began to fiddle with it quite a bit. To my surprise all the interior lights started working! Apparently the switch contacts were a bit worn or dirty. I’ll order a new switch offline later tonight.
Troubleshooting Problem 3 / 4: The temperature and oil pressure gauges do not work
To find the solution to my temperature and oil pressure gauge issue was pretty easy. Because I traced out the aftermarket temperature and oil pressure gauges earlier, I practically already knew that the signal wire was the issue. As I discovered earlier, the aftermarket gauges were directly connected to the temp sensor and oil pressure sensor with no t-taps. I metered out the steady hot and grounds just to be sure they were in working order. As expected, they were. I’ll hunt down where the signal wires were disconnected and reconnected them later. I’ll also have to get the factory electric oil pressure sensor as well. The previous owner preferred to run a mechanical line to the sensor.
Thank you all for you help and suggestions. Now I need some help replacing my door pins and aligning my doors!
