You will need to follow the brown wire from the headlamp switch to the fuse panel.

 

OK! I will do that... to be continued.

 

Does this sound like it will work for my problem?
EL Dash light repair
In a previous append I was lamenting the fact that my electroluminesent dash lights had failed, as has happened to many of you, and the only apparent remedy was a new gauge cluster. Well lucky for us that is not necessarily the case. This fix costs less than $5 and about three hours labor.

Much better than $400 for a new cluster and $150 labor and programming fee.

The EL gauge face in a Lightning is activated, or "driven", by an inverter circuit that boosts the truck's 12 volt system up to approximately 120 volts. The circuit also takes the DC signal and pulses it to approximately 400 hz. Most of these types of circuits are protected by a fuse and, fortunately for us, so is this one. Let me make clear that this is not one of the fuses that is in the access panel under the dash or under the hood. This fuse is in the inverter circuit.

The inverter circuit (board) is packaged seperately inside the gauge cluster and can be removed and repaired. You will need to remove the cluster from the vehicle. Before you do any work disconnect the (-) ground side of the battery. You will need to remove the black dash plate around the stearing column, the headlight switch, the black dash panel that the headlight switch mounts into, the large dash panel above the instument cluster and the black circular panel around the radio control panel. The headlight switch is easy to remove but tricky, you need to know how. Turn the headlight switch **** to the "on" position. Pull the **** out like you are turning on the fog lamps. Look on the underside of the **** and you will see a small square access hole. Inside that hole is a snap that needs to be released. Insert a tooth pick into the hole while pulling out on the ****. Be carefull, the snap is fragile. The **** should slide off. The **** is now used as a tool to remove the headlight switch. Turn the **** 180 degrees and place it back on the switch stem. Turning the **** will disengage the hooks that retain the switch. You're past the difficult part, the rest is fairly straight forward.

After you have all the dash panels off you can loosen the cluster by removing 4 screws. At this point make sure that you are grounded to the truck. Attach a wire to a piece of sheet metal under the dash and then strip the insulation off the remaining end and put it inside your sock and make sure that the wire is in contact with your skin. The PATS module in the cluster is ESD sensitive. You don't want to go to all the trouble of fixing the inverter but zap the security module in the process.

At this point you need to remove the cable that operates the shift indicator dial in the cluster. A small black cable runs from the bottom of the cluster down underneath the steering column and then attaches to a hook that is attached to the transmission shift lever. Disconnect the cable from the shift lever. Disconnect the two wiring harness connectors and the vaccum line for the boost gauge. The rubber boot that attaches the vaccum line was suprisingly difficult to remove but if you turn it a bit while pulling, it should come off of the gauge barb.

At this point the cluster should lift out of the dash. Place the cluster face down and remove the white plastic back cover. You should see a three wire connector next to where the boost gauge fitting is. This connector is for the inverter module. Disconnect the inverter connector and the connector for the odometer and
remove the cluster board.

Place the board on something soft like foam rubber or a conductive ESD bag if you have one. Remember this board must be protected from static charges or your security module is toast.

Remove the plastic panel that covers the inner gauges. Try not to let the clear plastic front lense or the gauge face seperate. All you want to remove is the white panel. When the panel is removed you will see that the three wire connecter leads go to a black plastic cube attached to the inside of the panel with two screws. This is the inverter. Disconnect the two wire connector from the EL panel and remove two screws. Luckily FORD did not pot the whole circuit or we would be out of luck.

You should be able to see the EL driver board and all of it's components. Notice where the three wire connector wires attach to the board. Next to this attachment point is a green component that should have "LF 1/4 amp " printed on it. This is a 1/4 amp Littelfuse. Meter across this fuse and hopefully you find that it is open. This fuse is Littelfuse P/N R251.250. It is a fast blow , axial lead , 1/4 amp fuse. At this point all you need to do is buy a fuse from Newark Electronics or some other supplier and install it. I would suggest not trying to put a larger fuse in thinking that it will prevent it from blowing again. The fuse may very well have saved the coil or the transistor that chops the signal and both of those would have been much harder to replace. Put a 1/4 amp back in and if it blows again several years from now, well , just replace it again.

 

Do your other instrument illuminations work ?

this would be the radio, glove box, ash tray, etc.

Considering that Fuse #18 is not getting power, this shows the problem is further upstream of the cluster, and I would suspect that the other instrumentation illumination does not work ( Fuse #18 is for the instrument illumination, and it is dead )

 

The odometer illuminates, the radio illuminates, and the climate control illuminates.

 

And you have no power to fuse #18 ?

Are you sure you had a good ground and were on the pin on the back of the fuse when you tested it ?

 

yes sir

 

i am confused and at this point have no idea what is going on.

 

I don't know the wiring off the top of my head but from what SSCULY is saying, next I would pull fuse 18 and see if the odo, radio, and climate control stay lit. If so then I guess that fuse doesn't control that and the problem is likely before that fuse(check headlamp switch, brown wire). If the odo, radio, climate control back-lights go out, then you must be measuring something wrong on fuse 18.

 

with fuse #18 pulled these lights illuminate. They will not illuminate with the dimmer switch connection pulled though.

 

The brown wire at the headlamp switch is hot.

 

Then you are not pulling Central Junction Box Fuse #18.

Diagram in Post #12 above. The pages -2, -3 & -4 are for the clock spring illumination, door lock switches, ( radio is shown on 71-1 ), etc.

Check your owners manual for the orientation of the fuse panel, you off on the fuse.

It would be, from the main headlamp switch it goes to the parking lamps and to CJB Fuse #18.

Back to the topic, if the odometer has a back light, and all the other instrument illumination works, you might want to check the cluster for burnt out bulbs and with the info above.

Still a bit confused about how you do not have voltage at the back of the switch, but the instrumentation illumination works.

 

at this point i am totally confused.

 

#18 is in the second row from the drivers side door towards the bottom. It has an unused space above and below it. It is a 5amp fuse. correct?

 

So I was trying to mess with my truck some more and in all my previous testing and proding I blew the #6 fuse in the engine compartment. Replaced that fuse and now have power to #18 fuse in the CJB. Still no instrument cluster illumination.