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Wiring and speedometer issues, Update

1321 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 small white plastic gear set that is replaceable ( if the parts are still available ) are just for the odometer operation. the speedometer itself is run by a small electric motor that is controlled by the signal from the VSS. you do not have to pull the cluster from the dash to remove the speedometer. it pulls out towards the steering wheel when you get enough screws out (four if i remember right). it has to come straight towards you because of the electrical connections. the speedometer can be taken apart. parts of it are very delicate. when i took mine apart, the motor that controls the speedo needle fell apart in my hands. i found a used cluster and swapped parts until i had a working speedometer. you may want to go ahead and pull the cluster and closely inspect everything. the wiring, the connections, the circuit boards etc. if you haven't already done that. you can go ahead and upgrade your dash lights while you are there. i put in LED's. probably not worth taking apart just to do that - mine didn't improve all that much. the factory service manual has some good tips on trouble shooting the gauges and is good for helping to understand how it all works. if your odometer gears have never been replaced they are probably toast - the plastic on the original ones are not very good. make sure you shop around for those gears - some of the prices are outrageous!
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i dont know if the VSS uses a hot wire or a ground but one wire would be "to" the sensor and the other wire would be "from" the sensor. there are three electrical connections to the speedometer. one is 12v constant with the key on - one is constant ground and the other is the signal wire from the VSS.
you need to take the cluster out and look at everything. the dash lights not working could be anything from burnt out bulbs to your light switch. the speedometer is not on the same circuit as the lights. the gears only operate the odometer. the speedometer is operated by a small electric motor.
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