Instrument cluster not working properly?

1SLICKDADDY

MEMBER
2006 DODGE DAKOTA
4.7L
V8
4WD
AUTOMATIC
142,000 MILES

I removed the gauge cluster from my vehicle (to the point of having dials off to separate the board from rear case) with intentions of changing the bulb color then found out that's not possible with this truck.

After reinstalling everything my tachometer only went to 600 RPMs and speedometer to 16 MPH. At 55 MPH (as determined by GPS speedometer app), fuel gauge flat on empty but DTE on overhead showed 128 which I knew it said when I parked it so that still works fine, and temp gauge never moved.
I pulled back out to check the needles and had speedometer and temperature down too far. So, I corrected that and reassembled and plugged everything back up, popped a couple screws in to hold the light switch and gauge cluster on the dash and drove down the road this time on a 90ole round trip on which I shut the truck off and restarted 3 times during and 3 times since with no other changes.
Now my speedometer shows 3 miles under, tachometer sits at 4,000 RPMs at idle, temperature gauge is fine and no fuel gauge movement with now an estimated 18 gallons in the 24 gallon tank.
I made sure all dial needles were at zero when plugged in and mounted both times as well as learned from past experience with my Ram.
Any ideas what else I'm overlooking?

1 Reply

CARADIODOC

MECHANIC
33,881 POSTS

You're popping the pointers on at the wrong times. Unlike the old thermal and magnetic gauges of the past, these are "stepper" motors. They have four electromagnetic coils that are pulsed with varying voltages and polarities to set the armature to the desired position. (Idle speed motors on the throttle body work exactly the same way).

To set the pointers, start with the cluster connected but the pointers removed. You know the speedometer should read "0 mph" when you're standing still, so you know where to put that pointer. For the tach, some models leave the pointer at the last engine speed when you turn the ignition switch off. To address that, just turn the ignition switch back to "run" with the engine off. Install that pointer at "0". Watch if there are little stop pegs at "0". Don't get the pointer on the wrong side of that peg.

For the other gauges, install those pointers where they should be based on your prior experience. I like to press them on just enough to hold them in place at first. That makes it easy to get them off if one needs to be repositioned a little. For example, if it's normal to see the temperature gauge just a hair under the halfway point, install it that way with the engine warmed up. The fuel gauge is a little trickier. The only way to know when it should read exactly "empty" is to run it out of gas. I like mine to read a little below "empty" when I run out, but if you do that, be aware some models can require up to five gallons to get them to restart. Once restarted, that five-gallon minimum no longer applies. The fuel pump's pick-up screen sits in a small bowl to prevent gas from running away on corners when the level is real low. Once the engine is running, the excess gas being pumped goes back into the tank through the pressure regulator on the engine or inside the tank. That keeps that bowl full while driving. When you fill after running out, on my '88 Grand Caravan, for example, the gas being poured in dumps right into that bowl. A pint of gas is enough to restart the engine. On. My '94 Grand Caravan, the gas being poured in misses that bowl. This is where it takes at least five gallons for the level to get high enough to spill over into the bowl. At that point the pump has gas to pump and the engine will run. The bowl will be kept full and you can use up all of those five gallons.

To say that a simpler way, if you do run it out of gas to know where to set the pointer, don't panic if the engine doesn't run after you put some gas in. You may just need more gas that first time to get the engine restarted.