whe42 5 Report post Posted October 5 I have a 69 6cyl 250 mustang with standard guages. I don't get power to any of the wires going to the various receivers on engine and gas tank. I bought a new voltage regulator and tested it with voltmeter and worked. I'm not sure where else to check. The circuit board is new as well but not sure if it is defective or how to test. Or perhaps if I need to look elsewhere. Any help would be appreciated. Quote Share this post Link to post Share on other sites
Midlife 838 Report post Posted October 6 Ahhhh...the well known (to some!) problem of 1969/70 gauges not working when replacing a circuit card. The gauges first pass through a small rectangular hole, then a cardboard rectangular piece fits over the two posts onto the metal housing, then the circuit card, then the two nuts which hold everything together. The problem? Any one of the gauges' posts can contact the metal housing without you seeing it, shorting all of the oil, water, and fuel gauges to ground, as they are all tied together with the CVR output. The ammeter is separate and MUST not touch the housing, as it will cause a dead short to either of the two hot and non-fused wires. How to test? Unsnap the battery snaps on the CVR and measure the resistance from any post of the oil/fuel/water gauges to the metal housing. You'll either see something very close to 0 ohms or 14 ohms, depending upon which post is shorted. How to fix? Loosen each gauge up, reposition, and retighten. Test again. This is a PITA as you don't know which gauge is shorting. Better solution is to remove the circuit card, then the cardboard insulated pad, and line each rectangular hole with black electrical tape. Put everything back together and you should be good to go. 3 Mach1 Driver, bigmal and TexasEd reacted to this Quote Share this post Link to post Share on other sites
whe42 5 Report post Posted October 6 Thanks ill try that this weekend when I can work on it again. Appreciate everyone's help Quote Share this post Link to post Share on other sites
whe42 5 Report post Posted October 14 So u were correct and system was grounding out on gas and temp guages. I have put tape down on metal but still grounding out at both guages. If I disconnect then oil guage works. So I know must be problem area. Not sure if there is something special I need to look at or just keep taping along metal. Thanks Quote Share this post Link to post Share on other sites
Mach1 Driver 597 Report post Posted October 14 I posted some pictures in your post on VMF. There is an insulator that goes on top of the metal housing before the flex circuit is attached. Quote Share this post Link to post Share on other sites
Midlife 838 Report post Posted October 15 7 hours ago, Mach1 Driver said: I posted some pictures in your post on VMF. There is an insulator that goes on top of the metal housing before the flex circuit is attached. That's needed, but doesn't ensure that either post of the gauge doesn't get offset and touch the metal housing. Quote Share this post Link to post Share on other sites
whe42 5 Report post Posted October 15 Thanks. I'll try bushings and see Quote Share this post Link to post Share on other sites
whe42 5 Report post Posted October 29 So i had tape on all the metal but tried bushings anyway and it worked! Not sure how as tape should have insulated everything but I'm not going to argue with success. Thanks 2 Mach1 Driver and RPM reacted to this Quote Share this post Link to post Share on other sites
