The Stovebolt Site Forums The Shop Area The Electrical Bay fuel sending wire?

my 66 chev. has what looks to be about a 16 ga. tan wire that runs from the fuel sending unit to the fuse box. but when i connect it to the fuse box the fuel gauge needle does'nt move and remains fixed @ rhs of full or F. unless i use a test light at the fuse box female port then the needle gives me a reading.anybody out there seen this before?

As memory serves me.....the tan wire goes directly to one side of your fuel gauge and an ignition source wire goes to the other side of your gauge.

let me re-phrase it.from the sending unit the tan wire travels towards the fuse box and has a female connector on the end of the wire which fits perfectly into the fuse box that reads fuel gauge ext.but nothing happens.fuel gauge needle stays or is stuck at past full reading. ican see that behind the gauge itself are two wires one black and one tan that conect to the back of the gauge.the ground is good from the fuel tank to the inside cab.

I've never heard of the sending unit wire going to a fuse. I'm not familiar with a '66 but every vehicle I've dealt with was connected directly to the gauge. I would think any fusing would be done on the other side of the gauge, between the gauge and the power source. Maybe someone with intimate knowledge of the '66 wiring will chime in.

The sending unit is a ground. There is no need for a ground to be fused. The wire should go to the gauge.

ok makes sence to me,but why then is there a port on the fuse box that says fuel gage ex?

Just guessing but possibly there was an option for an external auxiliary tank.

The tan 20 gauge wire DOES go directly to the fuse box on the '67 through '72 trucks! From the same terminal, another tan wire goes to the fuel gauge in the instrument cluster. The other side of the "Gauge Feed" is pink, 20 gauge and goes back to the fuse box. It sounds like you do have the correct wire as "Tan" has been the fuel wire color at least since 1956.

Wires "going to the fuse box" does NOT mean that they are fused! On the '67 -'72s the tan wire is just a "Feed Through," a way to plug in the wire. I really doubt there is much difference in a 1966 and a 1967, but there could be as the truck body changed at that year break!

The above info comes from the 1967 - 1972 Master Wiring Diagram from Chevrolet. If the wire was from an auxiliary tank, there would be two tan wires with a switch before the gauge.

There are lots of reasons why a gauge is inoperative. Open connections, bad sender, and bad gauge are some of them. Start at the 20 gauge pink going from the fuse box to the panel and trouble shoot from there.

best wishes,

Les

If you have, or can scan, the wiring diagrams for those years and send them to Keith Hardy at the Old Car Manual Project I'm positive he'd appreciate it. I went there to try to find a wiring diagram but he doesn't have anything yet that recent. It would help a lot of us.

well today i remove the only two grounding straps the truck has.firewall to block & cab to frame wire wheeled all ends and scraped all contact point and re-installed.no inprovement fuel gage pegs out @ past full reading.removed sending unit it looks perfect 30 oms clearly stamped on it. ran a jumper wire from sending unit stud to - grd just above fuel tank and the needle to the fuel guage jumpd to 1/8 empty and stays there until i remove wire or turn off key at which time needle slowly returns to past full. so now what?

You proved that the gauge works. It should have gone to empty but there may have been some resistance from your jumpers.

Next check the sender with an ohmmeter.

Way to go Dave! Fixing grounds, even if it doesn't solve the problem, is always a good thing. I don't know your truck, but is there any way that the wiring to the gauge could have become reversed? Just a thought. 1966 - 1967 is the change point for 30ohms to 90ohms. I wonder if you have a 90ohm gauge and a 30 ohm sender? I doubt it, though. It really sounds like something is reversed. If you have an aftermarket sender, it COULD maybe be the wrong polarity. There are both positive and negative ground senders. I can't think of anything else right now. Good Luck!

Les

to dark out side now. but tomorrow i'll give it a try in the daylight. i can see that behind the factory gauge there are two male prongs which mate w/a black 90 degree female fitting.i'll pull it off and rotate it 180 and see what happens i just don't ever remember removing the female fitting in the past.but we'll see. what a test of one patience this one is.