Help!! Tach problems have me stumped

[Mike Lammert]

Hello everyone, and thanks in advance for your input. I have been reading this forum and scanning it for answers to my questions for a couple of years now, but now i was looking for a little more 1 on 1 help. First off, I have a 1993 Johnson 115 model 115TLATS. I am getting no movement out of my tach needle. After reading this forum I learned that the tach gets its signal from the regulator/rectifier, which also controls the charging of the battery. After noting that my voltage didn't change with the engine running, I removed the grey wire from the electrical strip and hooked it on the yellow/grey wire and tach works fine.......So, I ordered a new reg/rec (CDI 193-4204), and with it now installed I still get no tach movement with the grey hooked to grey, but it still does work with grey hooked to yellow.....I am getting 6 volts on the purple wire, and only .15 volts on the grey wire......anyone have ideas?

 

[clanton]

Re: Help!! Tach problems have me stumped

Purple wire should be 12 volts. This wire is powered from the ignition switch.

 

[Mike Lammert]

Re: Help!! Tach problems have me stumped

Clanton-
Thanks for your post..I know there should be 12 volts on the purple wire, but do you think the ignition switch could be faulty and only allowing 6 volts? do you think this is affecting the tach? remember it works when the grey wire is tied in with yellow...going to keep tinkering with it tomorrow....I'll hopefully post more info when I get back at it!

 

[Mike Lammert]

Re: Help!! Tach problems have me stumped

Problem solved!!! After taking apart the control box, I found I was getting 12 volts at the back of the key switch, I started tracing the purple wire backwards from the engine, and as I removed the miles of electrical tape from the length of the engine harness, about 2 inches before the big red connector, the purple wire had been eaten completely through, insulation and all, by white/green corrosion. I guess the corrosion was still allowing about 6volts through. I cut the bad section out and used a jumper wire to reconnect, started engine, tach works great! I believe I am just going to replace the whole harness to assure smooth running in the future!