I have a 1978 f150, no dash lights. Gauges, seatbelt light, hybeam indicator light all work.Took cluster off an tested all the bulbs an they are all good. Checked an clean all the contacts on the circuit board as well the bulb holders. Someone had mentioned that the tail lights are on the same circuit as the dash lights. I haven't replace the tail light plug harnesses yet. Can anyone confirm that (they) are on the same circuit? Headlight switch had been replaced.

 

Pretty typical for the gauge lights to share the fuse with the tail lights.
Could be a stupid question, but did you try rotating the light switch counter-clockwise to full-on bright?
And if there's LEDs in there, they are polarity-sensitive, and would need to be installed 180º opposite to how they are now.

Is the back of your gauge cluster disintegrating at all?

 

No expert here but my newly purchased 78 had hit or miss dash lights -some worked, some didn't. I did a shade tree repair with JB weld on my deteriorated gauge cluster to improve the lamp holders/printed circuit board contact. Be sure to gently clean the mating contact areas on both. Huge improvement but the most bang for the buck is to insure a good cab to engine block ground. This in itself made a huge improvement to light and gauge performance. Good Luck!

 

Yes I rotated dimmer switch back an forth, no LEDS

 

Does your HVAC controls and/or the 'labels' for your headlights and wipers light up? If so, we know that the general circuit is OK. If not, then it could be a little more difficult to troubleshoot. If this is the case, make sure the cluster shell/back isn't eroding where the two gauge light bulbs go. That can cause a loss of electrical contact.

If you have a multimeter, try checking continuity at the bulb holders' contacts, where they contact the Instrument Panel Printed Circuit Board. The bulb holders can go bad, from the IP PCB contacts losing tension, or breaking off. You can bend them so that they make a good contact against the PCB, but they might break off - but you can always get new ones.

Another possible culprit is where the wire harness plugs into the PCB. You can check for continuity in a manner which includes the harness connector and PCB, but make sure there is no power in the circuit, or better yet, disconnect the battery for this if using the continuity function.

If none of those finds a fault, the next step is to trace the circuit through the headlight switch, and back to the fuse box.

And you should pull out the fuse to check it, and then clean the fuse-box contacts and corresponding surfaces of the fuse if it's good, because the contacts can glaze up with corrosion and break the circuit, despite an unburnt fuse.



I sanded every contact I could, form the bulb holders to the PCP, to the headlight switch and connector, and highbeam switch and its connector. I was rewarded with slightly brighter lights.

And when you do get them working, skip the 194 bulbs, and go with 168s. 168s are brighter, and these trucks, like other old Fords, need all the help they can get, when it comes to the gauge lights.