Wiring issues...
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Senior User
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Wiring issues...
I got my 74 F100 from a friend, warmed over 390 and rebuilt C6, all in great shape.
What wasn't in such great shape was my non-gearhead buddy took it upon himself to wire in a new fuse box with the 80s style fuses, ran all sorts of dedicated power cords for amps, ran speaker wires with splices in between the dash and the panel, smoked a really nice stereo doing that...
I corrected some rodent rewiring under the hood, got my oil pressure gauge and temp gauge working, then they quit apparently at the same time my alternator quit charging. Fuel gauge doesn't work at all, not sure if it is a problem with the sending unit or under the dash. Likely a dash problem going by the other gauges.
I was thinking maybe something had lost connection to the ignition switch, but the stereo and fan still work.
Any advice before I rewire the rest of the truck would be appreciated.
What wasn't in such great shape was my non-gearhead buddy took it upon himself to wire in a new fuse box with the 80s style fuses, ran all sorts of dedicated power cords for amps, ran speaker wires with splices in between the dash and the panel, smoked a really nice stereo doing that...
I corrected some rodent rewiring under the hood, got my oil pressure gauge and temp gauge working, then they quit apparently at the same time my alternator quit charging. Fuel gauge doesn't work at all, not sure if it is a problem with the sending unit or under the dash. Likely a dash problem going by the other gauges.
I was thinking maybe something had lost connection to the ignition switch, but the stereo and fan still work.
Any advice before I rewire the rest of the truck would be appreciated.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Honestly, knowing that a previous owner hacked up the original wiring beyond recognition, there's not much any of us can do over the internet with all the variables at play. We can help explain how it should or used to be, but that's likely very different than what you're working with now. Going through the entire truck like you describe is probably a realistic path.
That being said, if the oil/temp/fuel gauges all don't work, the first thing to check is the output of the ICVR on the back of the cluster. If you turn the key on and pull the lead off any of the three sending units and hook up a test light, you should see the light blink about once per second. That at least lets you know the ICVR is up and running.
That being said, if the oil/temp/fuel gauges all don't work, the first thing to check is the output of the ICVR on the back of the cluster. If you turn the key on and pull the lead off any of the three sending units and hook up a test light, you should see the light blink about once per second. That at least lets you know the ICVR is up and running.
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Thanks. That is exactly the sort of thing I needed.
I'm more confident that I could wire the truck from scratch than I am that I could sort this out, but I'd like to get it driving again this weekend. The alt at least worked last weekend.
I'm more confident that I could wire the truck from scratch than I am that I could sort this out, but I'd like to get it driving again this weekend. The alt at least worked last weekend.
Elder User
Joined: May 2004
Posts: 836
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From: Shreveport, LA
Personally, unless huge chunks are physically missing, I think it'd be easier to use what's there. If you decide to fully re-wire, save everything you remove 'till youre positive you wont need it, several hundred miles down the road. I've had good luck with EZ Wiring and their prices are great.
You can trouble shoot your fuel gauge by pulling the connector from your sending unit and putting a jumper between the pins in there while you watch your gauge; If it moves, your gauge is OK and the problems are in your sending unit.
If it doesnt move, you can keep the jumper there and go check continuity between the plug at your gauge cluster and ground; If you have a circuit, then the wiring is OK and your gauge is at fault.
Since youre fooling with wiring, sit back for a while and consider what changes you may want to put in right now; 3G alternator, head lamp relays, electric fans and Electrolux fridges are all easier and cleaner to put in when you've got it all torn down anyhow, rather than digging into things after they are all buttoned up.
Good luck with it either way!
You can trouble shoot your fuel gauge by pulling the connector from your sending unit and putting a jumper between the pins in there while you watch your gauge; If it moves, your gauge is OK and the problems are in your sending unit.
If it doesnt move, you can keep the jumper there and go check continuity between the plug at your gauge cluster and ground; If you have a circuit, then the wiring is OK and your gauge is at fault.
Since youre fooling with wiring, sit back for a while and consider what changes you may want to put in right now; 3G alternator, head lamp relays, electric fans and Electrolux fridges are all easier and cleaner to put in when you've got it all torn down anyhow, rather than digging into things after they are all buttoned up.
Good luck with it either way!
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Can you describe the specific symptoms? The idea that the alternator is not charging is a suspected cause, but does not give any actual information as to what's going on. How are you determining failure? Is it slow to turn over after having sat? Are you looking at the running battery voltage? What's actually going on?
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It was dragging when cranking, had to get jumped twice, checked the voltage, 11.7 running, 11.9 off. I haven't checked the alt itself yet, I've got spare voltage regulators to try.
I'm new to Ford trucks, but I've been working on cars for years.
I'm new to Ford trucks, but I've been working on cars for years.
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Update.
I fixed it a couple of weeks ago, figured I'd update.
The voltage regulator had worked itself *just* loose enough that it wouldn't charge, weak ground, the oil sending unit connector just fell off the oil sending unit and I had the wrong wire connected to the temp sending unit after the whole varmint chewing situation.
Everything works now but the gas gauge, which isn't too terrible. I live about 5 miles out of town, as long as I fill up the tank every time I drive past the gas station I have just enough to make it back to town... lol
Seriously though, it is single digit mileage. I'm going to fix the gas gauge and get an Edel kit to tune it.
I fixed it a couple of weeks ago, figured I'd update.
The voltage regulator had worked itself *just* loose enough that it wouldn't charge, weak ground, the oil sending unit connector just fell off the oil sending unit and I had the wrong wire connected to the temp sending unit after the whole varmint chewing situation.
Everything works now but the gas gauge, which isn't too terrible. I live about 5 miles out of town, as long as I fill up the tank every time I drive past the gas station I have just enough to make it back to town... lol
Seriously though, it is single digit mileage. I'm going to fix the gas gauge and get an Edel kit to tune it.
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