dome light question

[redneckaggie]

does anyone have good electrical prints of what pin on the headlight switch is the outgoing power to the interior dome light? In other words what wire gets power when you twist the knob all the way over past the click and the dome light should come on. Wire color would be nice as well. My dome light fuse has been mia for a while now because it had a short in the wiring. Now I have the truck apart and would like to make it functional again as well as use that wire to kick a relay for some other lights.

So I need either pin number, wire color, or a print if you could please.

 

[LCAM-01XA]

does anyone have good electrical prints of what pin on the headlight switch is the outgoing power to the interior dome light? In other words what wire gets power when you twist the knob all the way over past the click and the dome light should come on. Wire color would be nice as well. My dome light fuse has been mia for a while now because it had a short in the wiring. Now I have the truck apart and would like to make it functional again as well as use that wire to kick a relay for some other lights.

So I need either pin number, wire color, or a print if you could please.

The headlights switch does not actually power up your dome light when you turn it all the way to the left, instead it powers the cargo light circuit (black/pink wires) which then feeds into the dome lights circuit (black/blue wires) thru a diode. The diode is located towards the end of the whole harness, about 2" further in from where the wires for the dome/map and the cargo lights split. Removal of the cargo light is necessary to gain access to that area of the cab and its wiring.


The rest of the interior lighting circuit is as follows:

1) you have constant hot on all your green/yellow wires. They are used to feed battery power to the map lights, the door jamb switches, and the part of the headlights switch that turns the cargo light on and off. Cargo light then powers dome light as described above.

2) the door jamb switches power outs toward the dome light are black/blue. These get 12V when you open a door, and make your dome light come on. No current is backfed from the dome light into the cargo light due to diode mentioned earlier.

3) driver's door jamb switch will have a third wire in the connector, a red one, it's for the chime that tells you the headlights are on or you forgot your keys in the ignition.


Thus if you look at the dome/map/cargo lights harness running inside your door sill, you'll have 4 wires - green/yellow (battery power) for your map lights power, black/blue (switched at the door jambs) for your dome light only power, black/pink for your cargo light (and dome light thru that diode) power, and solid black for your cargo light ground. Only the cargo light gets its own ground, as its bulb lives in plastic connector inserted in a plastic housing - dome/map lights assembly attaches to the cab sheetmetal directly and grounds to it through one of the three mounting screws, thus no need for separate ground wire.


So if you're looking at your headlights switch, the green/yellow is your battery feed thru the fuse panel, and the black/pink is the switched power for the cargo light (and the dome light thru the diode).


Some simple tests:

1) put new fuse in, while having all doors closed and cargo light turned off. If it blows right away you have a short to ground somewhere in the green/yellow wires. Prime suspect would be harnesses for door jamb switches, as they have to go thru some quite sharp sheetmetal edges. Door jamb switches may have corroded internally too, tho that usually just disables then rather than shorting them out. If they all check out good, next up is the harness running thru driver-side door sill.

2) open doors one at a time. If one makes the fuse blow, check its door jamb switch harness for rubbed thru black/blue wire. If all doors make fuse blow, problem is in the black/blue wiring somewhere. Inspect aforementioned doorsill harness, and then up in the cab ceiling are between dome and cargo lights. Pull cargo light and look in thru its opening and check if any of the dome light screws is too long and touching the outer layer of cab sheetmetal (that actually can cause instant blow of fuse as well, if the too long screw is the one for the map lights.

3) turn cargo light on. If fuse blows, you have a short to ground in the black/pink wire for the cargo light. Inspect doorsill harness again. Then pull cargo light, and see if its black/pink wire rubbed thru on some of the sheetmetal in the hole there.


Clear as mud?

 

[redneckaggie]

thanks a lot for all of the info im pretty sure the problem is the wiring right behind the dome light because it blew the fuse randomly while going down bumpy roads a few times and when I started playing with all of the above mentioned wiring a while back it blew as soon as i pushed on the wiring going into the dome light. but I have the interior of the truck completely dissasembled now so I figure no better time to check everything out than now.

I really appreciate the help

 

[LCAM-01XA]

Sounds like your green/yellow wire is damaged, it's the only one up there that's hot at all times. Could be the dome light screw for it is too long, seen it quite a few times. Pull the cargo light and take a peek from its opening, you'll see right away if it's a screw length issue. You can also pull quite a bit of the harness out thru the hole to inspect wiring insulation more closely.

 

[91idi]

Mine had trouble where it goes up the b pillar. Check there

 

[LCAM-01XA]

Mine had trouble where it goes up the b pillar. Check there

So did mine actually, my black/blue wire (switched for dome light when doors are open) was corroded and broken off right as it exits the connector.

But he said the fuse blew when he pushed on the dome light, which is a very long distance from the B-pillar connector, so I hazarded a guess his issue is likely in the cavity between the dome light and the cargo lamp, rather than down where I (and apparently you as well) encountered it.

 

[redneckaggie]

yes sir seems that way but I have to get the rusty floorboards taken care of so that I can move on to this other stuff. again I thank you both for the help

 

[mf7lakes]

opposit situ - no dome

So did mine actually, my black/blue wire (switched for dome light when doors are open) was corroded and broken off right as it exits the connector.

But he said the fuse blew when he pushed on the dome light, which is a very long distance from the B-pillar connector, so I hazarded a guess his issue is likely in the cavity between the dome light and the cargo lamp, rather than down where I (and apparently you as well) encountered it.

so i haven't had a dome/cargo lite for a long while -- except owhen pax side fwd door is open, then dome comes on.

not with any other door - not with the headlight sw - all the door switches have continuity w/no corrosion.

But -- I've never checked this "B-Pillar connector" -- is this the pillar behind drivers left elbow in front of left back seat?

I'm thinkin' it got wet along time ago and 3 doors + headlite sw hasn't worked since. Hints (please)???

 

[LCAM-01XA]

so i haven't had a dome/cargo lite for a long while -- except owhen pax side fwd door is open, then dome comes on.

not with any other door - not with the headlight sw - all the door switches have continuity w/no corrosion.

But -- I've never checked this "B-Pillar connector" -- is this the pillar behind drivers left elbow in front of left back seat?

I'm thinkin' it got wet along time ago and 3 doors + headlite sw hasn't worked since. Hints (please)???

You people will make me have wiring nightmares soon enough, lol. The fact your dome light works with one of the doors is an indicator that the black/blue wire in harness running down the driver side door sill is intact at least from the connector behind the kick panel to the left of driver's feet all the way to the dome light assembly. Do your map lights work as well? If yes the green/yellow wire in the same harness is good as well.

1) undo dash panels, remove headlights switch but leave it connected to harness, verify constant hot on its green/yellow wire. If no voltage you have a problem in the harness, likely splice S214 (EVTM says it's burried in the main harness, near the tape-out for the headlights switch, so you might as well give up trying to find it as early as now).

2) if there is voltage, turn switch know all the way to the left till it clicks and check for voltage on black pink wire - if no voltage replace headlights switch.

3) verify constant hot on green/yellow wires on door jamb switches. You may have to pull the switches out for this. Don't mess with the front passenger's switch, you already know it works. Actually how many door jamb switches do you have? My crew cab has four, and two dome/map lights assemblies, but I switched all four doors to power ones off a fully loaded '96 crew, so I'm no longer sure what was factory and what is my own add-ons. Additionally my EVTM only shows front door jamb switches, no rears. Anyways, if your front driver's switch has no constant hot then your problem is in its harness. It's powered by the same S214 splice as the headlights switch. Yes, the splice you will likely never find. So pray now you have 12V constant hot there. lol

4) with driver's door open but all other doors closed, and door jamb switch plugged in its harness, check for voltage at the black/blue wire - if no voltage replace switch. Repeat with other doors that have door jamb switches, remember to keep all doors other than the one you're working on closed.

5) pull driver side kick panel, locate connector C200 - it is black and has 6 wires on it (in 2x3 arrangement). Test green/yellow wires for constant hot both in and out of the connector (if your map lights work, skip the green/yellow wire probing, it's confirmed good). Turn headlights switch all the way to the left to the position that should turn the cargo lamp and the dome light on, then check for power on the black/pink wires both in and out of the connector. Do not waste time with black/blue wires, we already know they're good. Finally measure resistance between solid black wire again on both sides of connector, and a good ground, should be almost zero ohms.

6) remove driver's door sill cover panel, inspect harness for damage (should be none, it's quite well protected there).

7) pull interior panel off driver side B-pillar (the column between front and rear door), see if the harness heads up thru it or continues back towards rear of cab. If harness goes up look for connector C300 near the bottom of the column - it will be flat, grey in color, and have 4 wires on it. If harness goes back to rear of cab, follow it, connector C300 should then be at the base of the C-pillar (the column behind the rear door). Test wires on both sides of connector C300 the same way you did with connector C200 in step #5.

If everything so far checks out good then you got a wiring issue between connector C300 and the dome and cargo lamps.

 

[mf7lakes]

Thanks again LCAM -- your are definitely WIRED!!!!

I don't have any map lights -- but I intend on following instructs and will let you know here.......

I have 4 door jam switches......

 

[LCAM-01XA]

Lol, you have no idea how wired I am indeed - I just counted on my small truck I have personally added 20 relays so far, the crew ain't quite as bad but only cause it runs mostly LED lighting and its engine and transmission require no PCM.

If your '93 has 4 door jamb switches from the factory, maybe my rear ones were factory as well... My crew cab is a '92... F600 tho, so slightly different from what you're working with, but still close enough. The wire diagrams I was looking up were for my '90 regular cab. Crew cabs were definitely available in '90 so my EVTM should cover them as well, however I'm yet to see crew cabs mentioned anywhere in it, not even in the power locks section (which I know for a fact use different circuitry cause of the additional pair of door locks)... Eh who knows, wire colors are identical for what you and redneckaggie are doing tho.

Btw, when you say you have no map lights, do you mean they are inoperative, or you physically do not have them? Cause if they are inop you should do the green/yellow wire voltage checks on the C200 and C300 connectors. OTOH if you never had map lights from the factory, head down to your favorite U-Pull-It salvage yard and bring home the harness for the map/dome light assembly from a truck like yours (take everything from the C200 connector back all the way to the light fixtures, and then a map/dome lights assembly from either the same donor truck (or one like it) or a bubble-shaped Taurus - the green/yellow wire is already in your doorsill harness, Ford just cheaped out on the piece of harness between connector C300 and the dome light and instead terminated the constant hot at connector C300 which will have 4 wires coming in from door sill but only 3 heading up the cab pillar.

 

[mf7lakes]

LCAM

have not taken the drivers kick panel out nor the headlight sw. however, got into the left rear pax door sw and the B pillar - if I put a meter on G/y wire and a ground, should I read 12v? if door sw is made, should I read 12v between G/y wire and the B/lb wire?

I'm only seeing .25 volt at this point (that's 1/4 v). I'll take headlight sw out (but connected to harness) tomorrow along with the kick panel and the cargo light assy.

and I do not have any map lights at all - only dome light and cargo bed light.

also, on the driver's door sw, there are 3 wires - a red, a G/y and a B/lb wire...........

Thanks again for your tolerance.

 

[LCAM-01XA]

Driver's door jamb switch has the red wire to signal the warning chime you left that door open (so it makes noise when lights are on or key is in ignition). If you splice that red wire to the black/blue one, the chime will sound when any door is open, not just driver's.

When testing green/yellow wire, measure voltage between it and a good ground with the switch plunger pushed in (door closed), you should see 12V.

When testing black/blue wire, measure voltage between it and a good ground with the switch plunger pulled out by its spring (door open), you should see 12V.

If you measure between the green/yellow and black/blue with the door open, it's normal to see very little voltage, as they are now connected thru the switch and thus there is no voltage differential between them. I's like measuring voltage between two ends of the same wire really. At the same rate if you measure between green/yellow and black/blue with the door closed, you're likely to again see little voltage difference - this time there is actual voltage differential of 12V between the two wires, but since the black/blue is not a ground (it still has to pass thru the dome light before it reaches ground) it acts like an open circuit, thus giving you again zero (or close to it) volts at the meter. So always measure between one wire and a good ground, preferably the cab sheetmetal itself.

Make sense?