What is this wire? Glove Box, Ash Tray?

[mulletmobile]

OK question for the gurus out there. I pulled the glove box from my '71 F-250 and found this wire with a bulb in a socket with no home. I can't find anywhere for this little guy to call home. Any takers out there? I doubt it goes to the ash tray as it comes out of a harness on the passenger side of the radio with a brown wire that leads to the heater control unit. It has a little metal z clip on it that we know holds it to the side of a metal lip somewhere. It is a blue wire with a red tracer on it. I know on the other end of the heater and ashtray this wire also goes into the cigarette lighter if it had a light. Mine doesn't (or at least if it did, the PO canned it along the way) and the PO had ran a wire to rig power to the lighter. I pulled the cluster and found the blue w/white tracer wire for the lighter power hanging loose and solved that issue. Now if I could just find a light for the lighter!

At any rate, the original question: Where does the mystery blue/red tracer wire with the socket an bulb I found hanging loose behind the glove box go?
See below:

[Canonman67]

When you turn on your dash lights does the heater control panel light up? If not than that's where it goes.

[mulletmobile]

Hmmm, that is what I suspected it went to, but I could not see where it attached. I found on a schematic of the area where it looked like a light for the control unit, but I wasnt sure. Right now none of my dash lights work. Not sure why, checked all of the bulbs and found no issues. I have a gas gauge that is stuck on E for both tanks, no dash lights and the right turn indicator light in the dash does not work. I am at a loss on how to fix those issues. I may try a new headlight switch as that is fairly cheap, but not sure where to go after that.

Anyone with info on how to get the dash lights working? Did all trucks get the courtesy light in the ash tray or cigarette lighter? I also found where two green/yellow tracer wires come together into a bullet style connector under the dash but nothing plugs into them. behind the right side of the instrument panel I found a pair of blue/red tracer wires that also come together into a bullet style connector but nothing plugs into them either. Need some help sleuthing this out. Bought a color coded diagram and looked at all of the ones here with still no luck.

[Canonman67]

My truck is at the shop so I can't tell you how it goes. I'll check it out this weekend. As far as the dash lights go are they turned up all the way? Have you checked the fuses?

[66f250cs]

Light to illuminate the heater controls?

[mulletmobile]

Two things on my part I have discovered:
1) Regarding the cigarette lighter installed in my truck appears to be an aftermarket replacement. I am basing this on the fact it has no provision for a trim ring on the outside, it has no provision for a light housing with a wire running from the two blue/red tracer wires with a bullet connection to the light (discovered this on further detailed checks of not only the wiring diagrams, but also the dash wiring diagram that shows the back of the cluster and labels some of the wires by name (not by color). I compared that to the wiring color chart and the blue/red tracer is for dash lights (hence the blue/red tracer wire with a socket and bulb I started this whole thread about).

2) The wire in question for this threads existence most likely goes to the heater control head unit. In order to find out where it is supposed to be attached, I will probably have to pull the radio. I already have the glove box liner and the defrost hose for that side pulled so removing the radio will be a cinch. While I am in there I may just go ahead and order up a new radio that has AM/FM, Bluetooth, and iPod capabilities. I don't mind only AM, but we bought the truck as first vehicle for our soon to be 16 year old as his first car. He is slowly coming around although he has said when he heads off to college in two years he wants my Fusion...Fair trade I like the truck better anyhow

[mulletmobile]

My truck is at the shop so I can't tell you how it goes. I'll check it out this weekend. As far as the dash lights go are they turned up all the way? Have you checked the fuses?

Canonman67,
I do have the switch turned up all the way and all fuses are good. I suspect either the headlight switch as the back of the switch has some corrosion built up on it and it is the original, or possibly the voltage regulator. If it is neither of those, I am at a loss. There is no power to any of the lights in the cluster (except the left turn indicator in the cluster) nor the loose bulb hanging out of my glove box. If all fuses are good, Is it possible that the missing courtesy light from the lighter is messing up the circuit? I think my next course of action is to start with a new headlight switch as they run $13-$30 depending which grade you go with.

I have test meters but zero knowledge on how they work. Never learned, but think I am going to have to in order to solve this one.

As far as the gas gauge being pegged at zero, it is the only gauge not working at this time. Neither tanks register right now. I know the main tank registered, but was reading low, when I bought it. Not sure about the auxiliary tank reading (it is a factory installed tank with the switch for the gauge) but there is no movement when either is selected. The connections at the in-cab tank are dirty so I will be cleaning and possibly resealing the tank. Is it worth pulling the sender unit to replace it? I don't want to throw money at it, but the connection needs to be fixed and the seal looks like it could use replacing.

[mulletmobile]

Canonman67 and 66f250cs you are the winners and I found a pic of where it goes. Looks to be the bottom side of the heater control. Borrowed a photo from a current eBay auction for the heater control head. Below you will find the crudely circled suspect and where it should be properly located.

[mulletmobile]

I have to say what an absolute and utterly complete PITA this little light is to put back in the housing! Probably easier when you do not have factory or dealer A/C installed, but holy hell that took almost two hours with the glove box liner and defrost duct already removed! Now, I do not know if it is related, but suddenly all my dash lights began working (ok all except two or three).

I am wondering though, if the socket/bulb holder for the heater control light is metal and the socket it snaps into is metal, could it be that the circuit for the lights is not completed/grounded until that light is plugged into it's socket and therefore the other lights in-line from the dash down to it do not light up until metal/metal contact for grounding purposes? I am not great at reading all of the wiring diagrams, but amazing how it happened to start working once that light was plugged in.

Also noticed the rheostat, if I am calling it by the right name, on the back of the headlight switch has a lot of corrosion on it. I turned it back and forth several times and noticed the dash lights go in and out at times instead of fading. New one ordered up.

[Canonman67]

That light is grounded on the control assembly. You probably jiggled something in your efforts to get that light in which caused things to work again. I feel your pain, I'm in the process of refurbing my '70 and even with a new harness it's a pain to get everything working.