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Wiring and speedometer issues, Update

1311 Views 72 Replies 7 Participants Last post by  ViolenceJack
Good morning gang. Since last time I was here my D250 is running good. I do however have some problems still and cant find a clear cut answer online.

So my fuel gauge works, but when I start to move the truck it bounces HARD left to right. I know the gauge technically works because I added about 5 gallons of fuel to the tank and it went up. The dummy light for "low fuel" is on though.

The oil pressure(?) gauge is at zero and doesn't budge. The truck has oil.

I'm not 100% sure if the temp gauge works either, I haven't really let it run super long to get that hot. I did however put a new thermostat in because the old one was rusty and stuck shut.

The speedometer and odometer do not work either.

The dummy light for the parking brake and ABS both stay lit. I have messed with the connector by the e-brake and it appears to be intact, but when I move it by hand the dummy light gets a little dimmer.

My pawpaw had most of the dash apart and I really have no clue as to what all problems he was facing. He did have the red plug for the dummy light panel plugged into the gauge cluster, and the black gauge cluster plug just dangling. I'm gonna attach a couple pics of some plugs that I'm not sure about that were left unplugged with (seemingly) nowhere to plug into along with some loose wires just laying in the floor. And I have a picture of a little silver fella that gets HOT even when the truck isn't running. I have it unplugged because I don't want to walk outside to a burnt up truck. Also I am for some reason terrible at tracing wires. Its the one thing that absolutely overwhelms me.

Any help is appreciated.



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The fuel tank module has a adjustable slide and the screws do come loose, you might want to check that because the module might not be sitting on the the bottom like it's supposed to.

Check your vacuum it should be around 25hg's.. there is a low vacuum switch behind the left hood hinge the rubber line could have fallen off.

That hot cylinder is the light around the ignition switch so you can see where the key goes in the dark.

Most will put aftermarket gauges in, a fuel presser gauge is a important troubleshooting gauge. 15 psi is all you need.
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The oil pressure sending units do go bad.

If your fuel tank is full i'd just jack up the bed drivers side, and loosen the passenger side bolts enough to allow movement to raise the drivers side and also disconnect the fill tube.
Ok I’ll probably go get a replacement oil pressure sending unit from napa today. Along with a mechanical oil pressure gauge.

And I won’t be able to jack up the bed today, all the bolts are rusted to hell.

You see in the first picture called IMG 925, in the floor beside that chain is a red and black wire connected to nothing. I just followed it and it goes straight through the fire wall to the battery. Any idea what it was supposed to connect to? Or any of these vacant plugs?
That red and black wire doesn't look Factory to me, looks like maybe CB wires or some other accessories he might have added.
The VSS assembly and wiring is the issue alot on these older Dodges. Also the sppedo gears are know to break in the dash cluster.
My old 92 didn't work when I bought it so I just used my Garmon.
If it has the metal gearbox looking thing at the trans those can go bad.
Is yours a mechanical cable or electronic with wires to the dash?
About everyone just unplugs the black box to disable the RWAL valve, they usually never work.
The newer Dodges use the rear wheel speed sensor for the Speedometer but not the 1st and 2nd Gen's.

Have you checked for volts at the VSS wires?
You might try finding the ground wire for the VSS and ground it and see if the speedometer works.

The wipers could be a bad fusible link.
You might check the wiring schematics to be sure.
You found the problem, now just need to find a replacement.
Hey gang, is there a good foolproof way of taking the needles off the gauges? My voltage and temp gauge needles both broke off when I was trying to clean them 🙄 I will have to source some new ones i guess. Also after installing a junkyard speedo with new gears in it, my speedo works! And installing a new headlight switch all the backlights on the gauges work! Also found a cool old sony radio at the junkyard that surprisingly works too.
If you want the headlight switch to last you need to put the headlights on relays.
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There's info all over the Web and also you can buy kits with the relays that are plug and play. It'll make the headlights brighter also.
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