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Rudolph Diesel
Rudolph Diesel, ASE ,Master Heavy Truck Technichian
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A new question is answered every 9 seconds and the speedo isnt consistent..bounce

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I have a 2000 kenworth t800. Just bought it and the speedo isnt consistent. When doing say 70, it will read around sixty and then bounce around usually up. When I stand on it with the foot feed to the floor, it 90% of the time will bounce up to the accurate speed. I am using a gps to figure out my speed. Sometimes when the jakes are on, it will jump up to correct speed. I replaced the sensor on back of the tranny, to no avail. Also the fuel gauge will be correct for a while, then bounces down and back, and then to normal again. Thinking im having a ground issue, but not sure. Maybe a bared wire that has been worn thin.



Is the fuse box in the firewall panel cover is just behind the clutch pedal?

Or is it in the glove box left side?


Customer: replied 6 years ago.
behind the clutch pedal.

Great thanks!

Here is what i have seen with what your describing,

I have a lot of hours into this kind of problem and what i found (last place i looked)


Is the wind shield seal above the fuses box will leak and get the fuses wet

if you pull the fuse box out from the firewall you will see where the back of the fuse panel has gotten wet and then all the connectors need to be clean and the ground here too,

I have seen it where the speedo jumps around like a bad speed sensor.

lights stop working, gages work and don't work.


The seal around the windshield does not fit the best I have seen drivers com in saying the inside of the windshield is wet.

So i pull the windshield and seal run a bead of clear silicone around it and along where the fire wall is seam to the cab and put the seal and windshield back in,,

Then i aways pull the fuses box and clean that up too because down the road the gages and lights act up.


Let me know if i can help more!

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