lights & gauges

[laskaboots]

My restoration of my '77 FHC is nearly complete now after 2 years. The paint is polished, the tires are new, I finally got the clutch working by replacing the rubber hose with steel line, and I've even driven it around the block a few times. I have been reinstalling the running lights, and have run into a strange problem. When I slide the light switch on, my electric gauges go way off. The volt meter drops to zero, the temp and fuel go to max. I suspected a short in the wiring somewhere, but the tail and side marker lamps stay on (I havent connected the headlights yet). No fuses get blown, and when I slide the light switch off, the gauges return to normal. Then I disconnected ALL the leads to all the lights..same problem. Is there an interconnection somewhere that I cant trace?
I did not do a full off restoration, so the original wiring is still in place, unless the PO did some creative changes. thanks for reading.

[dmtrmp6]

Re your gauges problem, check out the flexible blue/coloured printed circuit track on rear of the instrument cluster. Had similar problem recently due to a break in the flexible track for the panel/gauge lights. When turned lights on, temp and fuel went to max (among other random faults, all fixed when track repaired).

Cause? The lights were earthing via one of the terminals on back of temp gauge. Particularly look at the circuit track near the top of the cluster, this is where you may inadvertantly place a hand during removal/bulb change and damage the circuit without noticing. May take some time to locate the actual break, look carefully. The fix? bypass the damaged area with a length of lightweight, flexible wire soldered into circuit and glued to the flex circuit with silicone. Clean the blue coating from the area of copper track to be soldered carefully, the copper tracks are bonded to a flexible substrate and the adhesive dries out, becomes brittle over the years. Rgds, Daryl M

[laskaboots]

thanks for the reply. I will try to look in that area this weekend if I get the chance. Weather here in Wisconsin went from 70's and 80's in April to 40's and constant rain in May. Problem has all the indications of a short, or a grounding problem so a fault in a circuit board could very well be the cause. Will let you know what I find. thanks again.

[Terry B]

I had the same problem in my 75 coupe, but it was easily fixed by putting the clock adjustment cable back in it's spot. When my Dad drove the car he had the habit of knocking the clock adjustment cable out of it's spot under the dash and it would spring to back towards the firewall. This would cause my gauges to peg and the directional lights on the dash would be on but not flashing. Return the cable, and everything worked perfectly.

Sounds crazy, but worth a look before taking the dash out.


Terry B

[dmtrmp6]

G'day laskaboots, did you manage to fix your erratic gauge problems? Rgds, Daryl M