thefraze_1020 Posted May 23, 2020 Author Share Posted May 23, 2020 As I mentioned, at that time the tach was not working, but all of the other gauges were. Yesterday, one of my buddies came over and experimented to try to fix the tach. The first thing I did was unplug the C169 connector on the driver's side inner fender. I then hooked up my multimeter to a ground (brake line coming out of the master cylinder has served as a good ground for me), and the positive lead to the green wire on the coil side of the connector. We started the engine up and I had about 13.5 volts to connector C169. So, the wiring that far was good. I then assumed it was a cluster problem. We removed the bezel and cluster, then removed the gauge itself from the cluster. I then set the tach on top of the air cleaner and ran alligator clips to it to test. A black wire from the ground post on the tach to the above-mentioned brake line. A green wire from the tach side of the coil to the "Sig" post on the tach. And finally a red wire from the positive battery terminal to the "B+" post on the tach. We started the engine and nothing. In desperation, I bumped the tach needle and it started to move like it was supposed to, although kind of sticky: Link to comment Share on other sites More sharing options...
thefraze_1020 Posted May 23, 2020 Author Share Posted May 23, 2020 I recall reading somewhere that one issue the gauges (tach in particular) have is sticky needles, gummed up inside. So I sprayed inside the needle hole on the face with electronic cleaner, moved the needle around and tested it again. This time the needle moved a lot smoother when the engine was running. With a working gauge finally, we reassembled the entire cluster and bezel in the dash, and started the engine again. The gauge now moves like it is supposed to! So, as it turns out, it never was an electrical problem, rather the needle on the tach itself was sticky. The next tasks are to try to bench test the digital clock and the radio. I have a good idea how to test the radio, but does anyone have a good way to test the clock? It's a 4-pin connector, but I am not sure which wire is which right off the top of my head. Link to comment Share on other sites More sharing options...
kramttocs Posted May 23, 2020 Share Posted May 23, 2020 The next tasks are to try to bench test the digital clock and the radio. I have a good idea how to test the radio, but does anyone have a good way to test the clock? It's a 4-pin connector, but I am not sure which wire is which right off the top of my head. Nice work on the tach! Check this out on the clock: http://www.garysgaragemahal.com/digital-clock1.html Link to comment Share on other sites More sharing options...
Sac79 Posted May 23, 2020 Share Posted May 23, 2020 The next tasks are to try to bench test the digital clock and the radio. I have a good idea how to test the radio, but does anyone have a good way to test the clock? It's a 4-pin connector, but I am not sure which wire is which right off the top of my head. Congrats on getting the tach to work. The W/P wire is power, should allow you to check the clock. LG/Y is memory and BR is to dim the display? I don't have one, so not sure what the brown does, but that's just my assumption going off the EVTM. Link to comment Share on other sites More sharing options...
thefraze_1020 Posted May 23, 2020 Author Share Posted May 23, 2020 Congrats on getting the tach to work. The W/P wire is power, should allow you to check the clock. LG/Y is memory and BR is to dim the display? I don't have one, so not sure what the brown does, but that's just my assumption going off the EVTM. If one of those clocks does not work, is there a common thing that goes wrong inside em? And if so, are they repairable? Link to comment Share on other sites More sharing options...
FuzzFace2 Posted May 23, 2020 Share Posted May 23, 2020 Congrats on getting the tach to work. The W/P wire is power, should allow you to check the clock. LG/Y is memory and BR is to dim the display? I don't have one, so not sure what the brown does, but that's just my assumption going off the EVTM. BR is the dash lights for diming BK (black)is a ground LG/Y power all the time memory W/P power with key to run & acc. Now I don't know what year truck you have as the colors on the truck changed over the years My 81 the BR wire for dash lights went to LB/R wire on the truck all the rest were the same colors. I cant help on if it does not work or how to fix as mine, from Ebay, worked when I hooked it up. Good luck Dave ---- Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 23, 2020 Share Posted May 23, 2020 I recall reading somewhere that one issue the gauges (tach in particular) have is sticky needles, gummed up inside. So I sprayed inside the needle hole on the face with electronic cleaner, moved the needle around and tested it again. This time the needle moved a lot smoother when the engine was running. With a working gauge finally, we reassembled the entire cluster and bezel in the dash, and started the engine again. The gauge now moves like it is supposed to! So, as it turns out, it never was an electrical problem, rather the needle on the tach itself was sticky. Really glad you've got it working! Sometimes Occam's Razor falls right into play. Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 23, 2020 Share Posted May 23, 2020 Really glad you've got it working! Sometimes Occam's Razor falls right into play. Well done on the tach! That may be the problem with other trucks as well. Link to comment Share on other sites More sharing options...
thefraze_1020 Posted May 23, 2020 Author Share Posted May 23, 2020 Well done on the tach! That may be the problem with other trucks as well. I tried testing the radio today, no dice. With that said, I tore apart the radio so if anyone needs bits for a 1985-86 AM/FM/Cassette electronic radio, let me know. I have a good faceplate, buttons, and the casing. Link to comment Share on other sites More sharing options...
thefraze_1020 Posted May 23, 2020 Author Share Posted May 23, 2020 I tried testing the radio today, no dice. With that said, I tore apart the radio so if anyone needs bits for a 1985-86 AM/FM/Cassette electronic radio, let me know. I have a good faceplate, buttons, and the casing. Oh, and Gary, we are moving next week. So, you can change my location to Burlington, WA 98233. Thank you! Link to comment Share on other sites More sharing options...
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