It is the same fuse as the radio illumination, mode switches, ashtray, etc
Cab fuse panel Fuse #18, 5A.
Shown in the diagram in post #16, the labeled 71-1

 

Ok i pulled the bulbs from the hvac and they were blown bought new ones but they are not lighting up, my fuses are good, checked them all, any ideas?

 

Do you have power at the bulb connector, with the dimmer switch all the way up, and the main headlamp switch at least in the park position.

 

yea no power at all at the connector, what do i do now?

 

Pull the switch out and test the output of the dimmer panel switch on the main headlamp connector. Directions above.

 

Everything looked good from a grounding standpoint so I jumpered voltage to LTBlu-Red and everything lit up just fine. This is on the 1998 Base. Time to get a new switch.

 

Actually this is a quicker test than testing the switch.

Pull the switch out, and jumper from the back side of the connector between the Dark Blue w/ White stripe the Light Blue w/ Red stripe wire.

All the lights excluding the radio should illuminate.

 

The thread that will not die....
If I read the illustration 071-001 right, there's supposed to be -2V at C245 Pin1 DB/W when park or head are on. Is that right?
Just thinking that that's bias voltage for the transistor in the switch to allow current to flow for the panel lights. If it isn't hefty enough to handle much and if pin 1 gets more than it can handle, I'll be blowing out switches. At $90 a piece, this could get expensive.

 

I think that is blurry: 12V in park or head.

If you look at the number 1 on the diagrams, on 71-1, look to the right where the A arrow is at.
The text is a bit more clear, and it say 71-1. The 1's do not have the bottom line on them in the diagrams.

 

SSCULLY, Thanks, my old eyes fool me sometimes, they could have used better printing. C245 and C246 look a bit the same sometimes.
Anyway, here's more info. I just couldn't let it alone. C245-5 T/W is 12V, C245-4 BR goes to 12V when at park, as per 71-001. However, C245-1 DB/W is .5-.7V, not the expected 12V.
S224 and C243 are in between but the fuse is OK. C242-7 to C245-1 is the only path that I know of.
The thought has crossed my mind to pull the switch connectors and to short 245-4&5 and see what gets hot but that's only a joke...I hope.
After lunch I'll pull the connector and check resistance between 245-1 and ground. Any advice?

 

SSCULLY--Here's a new twist. During my investigation I discovered that wiggleing fuse 18 brought back the Lights On Alarm. Pulling fuse 18 out a bit and the alarm worked, pushed all the way in and nothing. Dirty connection? Bad fuse?
Replaced the fuse. Panel light are back. Case closed.
Thanks for all your time.

 

Not sure on that one. Could be someone used one of those fuse taps that hook on the leg of the fuse, so the fuse slot is stretched out ?

That is just a SWAG at the moment, but if it is that loose, could be that or fuse with smaller bases ( never seen that myself )

 

The fuse contacts were worn smooth and shiny. I'll guess that 140000+ miles of vibrations had worn it smooth. The contacts of the new fuse seemed to be a bit thicker and made a stronger contact.
This is a Colorado ranch truck and I'm sure it's had a hard life and seen its share of bumpy travel.
Makes a case for changing all the fuses after a certain amount of time.
Thanks again for all your time and help. It was your postings that led to the answer.

 

Actually it was your work that lead to a solution. Might be very useful for the next member that has a similar problem.

 

Ok i got a question, like i said before when i had the radio apart two wires touched and that was when the lights went out, but i checked the fuses and they are good, im confused man