project nightmare Posted May 28, 2011 Report Share Posted May 28, 2011 Hey guys- I've been having a tough time figuring out why there are no dash lights in my 79 620. All running lights work but there are no lights in the dash/heater controls/wiper knob. Both the green/blue (pin 4) and green/black (pin 2) at the gauge cluster 12 pin plug have power and the blubs in the gauge cluster look good too. The green/blue wire leaving the headlight switch is good as well. The stock tach or clock was removed and replaced with an auto gauge unit so the 6 pin plug has been abandoned. I see there are a few wires that jump over to the gauge cluster. Would they have any effect on the illumination of the entire dash? Let me know what you think, thanks!! PS-What function does the black wire/cable coming out of the rear of the headlight switch serve? I think I saw one on the wiper switch too iirc Quote Link to comment
datzenmike Posted May 28, 2011 Report Share Posted May 28, 2011 Turn the dash illumination knob fully to the right. PS-What function does the black wire/cable coming out of the rear of the headlight switch serve? I think I saw one on the wiper switch too iirc Likely it's a fiber-optic cable that channels light from a common bulb source to the two switch knobs. (the bulb could be burned out) Quote Link to comment
project nightmare Posted May 30, 2011 Author Report Share Posted May 30, 2011 The knob is all the way to the right. Any other ideas? Interesting about the cable. It moves in and out with the knob Quote Link to comment
project nightmare Posted June 2, 2011 Author Report Share Posted June 2, 2011 Anyone? I've run out of ideas Could an electrical spike send the gauge cluster TU? Quote Link to comment
yello620 Posted June 2, 2011 Report Share Posted June 2, 2011 Hey guys- Both the green/blue (pin 4) and green/black (pin 2) at the gauge cluster 12 pin plug have power and the blubs in the gauge cluster look good too. The green/blue wire leaving the headlight switch is good as well. The green/blue wire is the power wire, so now you need to find the ground to the guage cluster and verify 12 volts between the two. I would start by replacing the bulbs with a known good bulb first, not one that just looks good. Interesting about the cable. It moves in and out with the knob The black cable is supposed to slide in and out, it is a fiber-optic cable. Follow it to the little round metal cylinder usually mounted below the wiper switch. This cylinder contains one bulb that lights up both the wiper switch and the headlight switch via the fiber-optic cable. Quote Link to comment
project nightmare Posted June 2, 2011 Author Report Share Posted June 2, 2011 Thanks! I do remember chasing the ground for the cluster at some point but don't remember my findings. How about checking the ground wire continuity? Quote Link to comment
yello620 Posted June 2, 2011 Report Share Posted June 2, 2011 That is basically what you are doing by verifying the ground at the guage cluster connector. If you dont have a propper ground there, then you need to find where you lost it. Quote Link to comment
project nightmare Posted June 8, 2011 Author Report Share Posted June 8, 2011 Dash bulbs are good and the ground wrie (pin 11) does not read open. Any other ideas? Quote Link to comment
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