Chiro

Unable to get dash lights to work on speed/tach or central
instrument cluster. Have replaced circuit boards, bulbs and
rheostat. All guages are working. Any suggestions as to what
the problem may be. Thanks.

65GGvert

The dash lighting only requires two things, 12 volts and ground. Measure on any of the bulbs with the light switch in the park or on positions. With the meter ground on a good ground, do you have 12 volts to the lamps? If so, ground the common side of the strip (or the metal case of the bulb) to a known good ground. The lights should come on. You need to find where the ground is lost. If you don't have 12 volts, go the other way. Do you have it to the light switch? If not, go toward the fuse box. If you have it on the switch, is it on the output side going toward the lamps? If so, you have a broken wire or bad connector that connects to the circuit assy's. It sounds like you don't have it coming out of the fuse box, but it's easy to check with a meter.
You need to find out which of the two requirements is missing, ground or 12 volts.

Durango_Boy

I don't have much advice for your problem other than what was already suggested, but I had a question about your name. Did you choose it because Chiro is Spanish for Bat?

Easy Mike

You do not list checking the fuse. I believe it's 5A and marked IP. Check your owner's manual.

65GGvert

I did mention to check for 12 volts and if not there, go to the fuse box. I also mentioned that maybe he didn't have the 12 volts coming out of the fuse box. That should take care of it.

454Can-Am

I'm not sure how GM worked it in 1978, but when I used an '80 harness in mine, I ended up with no speedo & tach lights ! It seems GM (with they're infinite wisdom) ran the power wires for them thru the windshield wiper switch ! Took me weeks to figure that one out !!! It's possible yours is run the same way. The center gauge lights have a different power source from what I remember........... so I don't know why they would all be out................ do you have the main headlight switch grounded ???

Hope this helps................ Good luck ! Rick

Chiro

I believe chiro is actually a greek word. I am a chiropractor which
explains the use of chiro. Take care.