Running a direct wire to Temp Gauge

[Chief Brody]

Have you disconnected the plug from the printed circuit board yet and inspected the circuit board termination where the plug makes contact? I had a vehicle once that gave me some fits and it turned out that as I had plugged the connector into the cluster one or more of the terminations from the circuit board got twisted up and where causing a short (it's been years ago and I can't remember exactly what was going on but it's definately something to check if you haven't already).

Yes...brand new circuit board from LMC....nice crisp and tight.

There is something that is puzzling me now....when I first found the correct wire on the schematic and attached that wire, the headlight switch stopped making the gauges move....
I am beginning to think that whatever is causing this gets "moved" or jarred....or something...in a weird way the headlight switch causing the gauges to move is sort of intermittent...however, I am not sure that the gauges are or ever have been acurate or working....I thought once that the temp gauge was...but I can't say for sure that the fuel gauge has ever worked correctly....

 

[Chief Brody]

Does the schematic show where the fuel gauge sending wire comes out of the firewall harness?

I don't see it.

 

[Fordum]

Well, it does and it doesn't.

While it shows the wire, it does not really show what it is for.
It is the 18T-30 wire in the corner socket.

Maybe these next two schematics will help

 

[Chief Brody]

Thank you...I found it and I cut it off midway to the gas tank and ran a new piece of wire and spliced it in to the wire coming out of the firewall.

It still didn't work.

So I tore out the instrument panel bucket again and looked at every wire going to the fuse block. I also looked at the floorboard high-beam switch and right beside it was an orange and a white wire going back to where the fiberglass top goes on.

I removed that wire, and it was attached to two white wires that go to each door light switch.

When I put it back together the gas and fuel now appear to working.

BUT, now the instrument cluster lights don't work.

The blinkers and the High-Beam indicator does work, but none of the lights that you can dim with the headlight switch work anymore.

 

[Chief Brody]

bmp

 

[Chief Brody]

Anybody here know if the accessory light and door switches are in any way responsible for the instrument cluster lamps working?

 

[Fordum]

OK, chief, sorry to leave you hanging, but I have a bitch of a day and was having to type with one hand, since my right was unusable.
So, I did not get on today like I usually do.

Still not 100% might have to postpone some of this until tomorrow.

The white wires you found go everywhere. Lots of splices and connectors. If you ground them anywhere, the inside lights should come on.

The dimable dash lights are controlled by the two farthest right pins on the dash schematic. Sockets 8 A-B and 11, with 11 being a light green, and 8 A and B being grey.

Not totally sure what is what, but I will examine it tomorrow.

Looking at the bottom of the cab inter schematic, you see the light switch, the two pins that the rheostat are hooked to are the controls for the dimable lights.

I am pretty sure that the 16DG-44 wire on the socket side supplies power to those lights. But, its runs lots of places and changes its name some.
I still don't have all the use of my hand, and it really hurts to type, so I am going to leave it up to you tonight.
Take your time, and trace that wire down, making notes of where it goes and what it changes into, and you may find the problem.

Those white wires you found do not have anything to do with that circuit except that one of them goes to the dome light switch on the headlight switch.

But is not hooked to anything else. That is about as close as they come.

 

[Chief Brody]

I'll have a look tomorrow. Today I bled the brakes and put on the nos hub dust covers.

I wonder how many times I have removed the instrument cluster already...has to be at least 20....

 

[Chief Brody]

I have looked at everything...I am completely stumped. I can hold a 12 volt battery to one of the bulb sockets on the instrument cluster and they all light up.

I even bought a new headlight switch...

 

[Chief Brody]

Whew! pulled the fuse block today and turned it around and cleaned every contact with sand paper and a wire brush and electronics cleaner.

I put it back together and voila!!! Success, so far. The dash lights come on and stay on, and the temp gauge and fuel gauges work!

I did not see anything that was obvious...no frayed wire, no short, no loose connections. The spade lugs were dusty and tarnished, the looked like new brass after I cleaned them. It was raining all day today so I couldn't drive it to see if it messed up the dash lights when I hit bumps in the road but I tapped the fuseblock and yanked on the wire harness and the lights still stayed on, so hopefully, this is solved.

 

[Fordum]

Sounds good. I'm getting the rain now.