Electrical question Dakota Digital dash install

[RW1977]

Installing my digital dash from Dakota. Needing to know what wires to use from the stock harness for the fuel positive and negative on the Dakota control box. Any help would be much appreciated!

[RW1977]

Truck is a 77 with dual tanks.

[ray_mcavoy]

If your truck originally had an idiot light cluster there will be 2 pink wires and 2 black wires on the cluster connector that are +12V and ground respectively. If your truck originally had a gauge cluster it will have 3 pink and 3 black wires.

You can use any one of the pink wires for the +12V feed ... they all tie back into the same spot in the harness and are switched on/off by the ignition switch. Just avoid the pink wire with a white stripe ... that one is for the seatbelt light.

Similarly, you can use any one of the black wires for the ground.

And I assume you'll need to connect to the fuel sending unit wire as well. That one is tan with no stripe. Not to be confused with the tan wire that has a white stripe ... that's for the brake warning light.

Even with dual tanks, there is only one tan wire for the fuel sending unit up at the cluster plug end. The other end of that wire plugs into the dual tank sub-harness that takes care of routing it to the dash switch and the two sending units.

[RW1977]

Ok from the plug I have 3 solid tan wires. 2 at #18 and one at #7. From reading here on the site it says there is a jumper from #18 wire back to #7. Will any 3 of these wires work for the +fuel send on the Dakota box or do I need to plug all 3 in? In the Dakota instructions it says the -fuel send needs to be grounded to the body of the sender unit. Will any of these grounds in the dash work for this or is it necessary to run a ground back to the tanks? Thanks for the insight!

[RW1977]

This is where I'm getting my info

http://67-72chevytrucks.com/vboard/s...d.php?t=425706

[ray_mcavoy]

Originally Posted by RW1977

Ok from the plug I have 3 solid tan wires. 2 at #18 and one at #7. From reading here on the site it says there is a jumper from #18 wire back to #7. Will any 3 of these wires work for the +fuel send on the Dakota box or do I need to plug all 3 in?

I forgot about that jumper in the fuel sender wire when I posted earlier.

The wire from the fuel sender is one of the two wires you're seeing doubled up on #18. The second wire on #18 is the jumper that goes over to #7. They were jumpered together like that from the factory so the plug would be compatible with both tach or non-tach gauge clusters.

If you're leaving the factory plug intact, you can splice into any one of those tan wires for the fuel sender connection. But if you are cutting off the factory plug, you can eliminate the jumper wire completely and only be left with the single tan wire that goes to the sending unit(s). You might have to unwrap some of the harness tape to completely remove the jumper wire.

Note that the factory also used a similar jumper wire setup on the tan w/white stripe wire for the brake warning light. That one is jumpered between #6 & #17. Also done to make the plug compatible with both tach & non-tach gauge clusters.

Originally Posted by RW1977

In the Dakota instructions it says the -fuel send needs to be grounded to the body of the sender unit. Will any of these grounds in the dash work for this or is it necessary to run a ground back to the tanks? Thanks for the insight!

Those black wires on the cluster plug all lead back to a factory splice in the cab harness that is grounded to the cab with a screw going through a ring terminal.

The fuel tank sending units each have a ground wire that attaches to the frame with a bolt through a ring terminal. And there is a ground strap that connects the cab to the frame (located near the left rear cab mount if I remember correctly).

So any of those black wires at the cluster plug should make a suitable ground. But it would be a good idea to double check all of those factory ground points to make sure the bolts/screws are all tight and that the connection points are free of rust, corrosion, or paint. Especially where the sending units ground to the frame and the cab to frame ground strap.

[RW1977]

Ok so either of the tan wires at 18 and any one of the 3 ground wires should get me what I need right? One last question. Will the grey wire for the dash lights only see 12v once the headlight switch is pulled out? I need a wire to dim the new dash when you turn the headlights on.

[ray_mcavoy]

Originally Posted by RW1977

Ok so either of the tan wires at 18 and any one of the 3 ground wires should get me what I need right?

As long as you leave both wires crimped together on the #18 terminal, you can safely splice into either one of them.

But if you cut the wires off the #18 terminal, that will separate the connection between the two and leave the section that jumpers over to #7 just "floating". You don't want to connect to that "floating" end.

If you cut the wires at #18, you can use a continuity tester (ohmmeter) to identify the now "floating" jumper section. Or simply untape the harness a bit and you should be able to see where it loops back to #7.

As for the 3 black ground wires, yes, any one of them will work. They all lead back to the same ground point in the cab.

Originally Posted by RW1977

One last question. Will the grey wire for the dash lights only see 12v once the headlight switch is pulled out? I need a wire to dim the new dash when you turn the headlights on.

Yes, the grey wire is only live when the headlight switch is on (both parking and headlight positions). It runs through a rheostat (variable resistor) in the headlight switch that varies the voltage to brighten and dim the dash lights. So it's only 12V when the knob is rotated to the max brightness position.

Does the Dakota digital dash have 2 different "lights on" / "dimmer" inputs? One being a 12V signal to indicate the lights are on. And the other being a variable voltage to determine the display brightness.

If so, I would wire it up like GM did with their digital radios in the 80's and early 90's. They tied into the brown wire on the headlight switch for the 12V signal that causes the display to dim when the lights are turned on. And they used the grey wire as the variable voltage that determines the brightness of the display.

[RW1977]

The Dakota box just has one input for the dimmer. You can buy a separate rotary dimmer switch to adjust the dim if you wanted. I'll just use the grey illumination circuit to dim the dash to the 50% they preset. I'm going to cut the factory plug off so it sounds like I should cut the #7 wire and trac it back to #18 and remove it and use the last tan for my fuel sender. Thanks for the help I think I should be able to finish it up now!

[ray_mcavoy]

Originally Posted by RW1977

I'll just use the grey illumination circuit to dim the dash to the 50% they preset.

That should work okay. However, if the Dakota dash needs full 12V (or close to it) to activate the dimmer you might have to turn the headlight switch knob up to the maximum brightness position.

Originally Posted by RW1977

I'm going to cut the factory plug off so it sounds like I should cut the #7 wire and trac it back to #18 and remove it and use the last tan for my fuel sender.

Yes, trace that tan wire back from #7 and remove that section of wire. That'll guarantee that the remaining tan wire from #18 is the one that goes to the sender(s).

Originally Posted by RW1977

Thanks for the help I think I should be able to finish it up now!

You're welcome!