ashleesmach1 28 Report post Posted October 1, 2019 I replace the printed circuit board and they don't work. I replaced the constant voltage unit and they still do not work. I put the old printed circuit board back on and they still do not work. I put the original constant voltage regulator and still no go. I want to bench test the original gauges.Can you suggest a good way. I know they work at 5vdc, so what's the solution? I really don't want to apply 12vdc to them. If they are truly dead then I will replace them. Thanks! I have a 69 Mustang Mach 1 btw Quote Share this post Link to post Share on other sites
Caseyrhe 650 Report post Posted October 1, 2019 Did you check the fuse Quote Share this post Link to post Share on other sites
Midlife 814 Report post Posted October 2, 2019 There is no fuse. What is wrong is that by replacing the circuit cards, you have to remove the retaining nut on the gauges. Underneath the circuit card is a cardboard insulator that slips over the two posts. There's enough slop in the gauge fitment into the cluster itself that it is EXTREMELY easy to have one of the posts contact the metal housing, particularly since you cannot see what is going on beneath the insulating pads, the circuit cards, and the retaining nuts. Once one of the posts contacts metal, all three gauges are essentially short-circuited. How to test? Measure the resistance from each post to ground: you should see kilo-ohms at worst. If you see 1 ohm or 13-14 ohms, then that post is grounded (1 ohm) or the other post is grounded (13-14 ohms). The input power to each of the gauges (oil, water, fuel) is common to all 3 gauges. This test is also essential for the ammeter; if any of the ammeter posts are grounded, you will quickly have a dead short to battery and a fire and smoke will result in seconds. If you see low resistance, loosen the retaining nuts and wiggle the gauge such that the posts are not contacting the side of the slot allowing the posts to stick through. Quote Share this post Link to post Share on other sites
ashleesmach1 28 Report post Posted October 2, 2019 The temp and fuel gauges were grounding against the metal case. I put electrical tape around the case edges where the gauge posts go through and the flat surface as well. This fixed the situation. I researched and found a u-tube video that gave me the idea. Problem solved, no more short to ground! I replaced the old printed circuit board and installed 5 led light bulbs blue red and green. and a solid state voltage regulator. I also replaced the lower steering wheel cover as the mounting holes broke as I barely touched them,. It must have gotten brittle. oh well.....lol Quote Share this post Link to post Share on other sites
