Where Does My Tach and Speedo Signal Come From?

[Panama]

I have a 1996 Yamaha 40 TLR U motor on a Cherokee boat. The dash has a digital info system it has had since new in 1996. It reads the tach, speedometer, miles driven, etc.

The two round dash digital gouges have lost power. They are blank. The 40 HP motor runs great. The accessories like horn and bilge pump all work. I checked the fuses and they are all good.

Does this power and reading come from the motor?? Does anybody know?? I think it might and there might be a fuse there....

I don't know... can anybody help??

[yam911]

Battery positive and negative and the tachometer signal itself come from the 10 pin harness that runs from the motor to control box. From there a jumper wire harness is connected to the tachometer wires. The jumper wire has a fuse. Could be the fuse. Could be a connection at one of the wire terminals.

[Panama]

20230124_124247.jpg

This is a picture of the gage. Neither gage is coming on. What would be the best place to look if NEITHER of the gages is coming on? They both went off at the same time. I want to do what is needed but I am 74 years old and getting under the console and out again is hard. I want to do the most likely and easiest things first. This little boat is 27 years old and has a sentimental quality to me. I really want to fix it if I can. Thank you for any help.

Since BOTH gages stopped at the same time, I wonder if there is a ground involved I should check. On the two fuses, wouldn't both fuses have to blow at once ?? Is one fuse for one gage and the other for the other gage?? Thank you for your time and help.

You can click on the little picture to enlarge it to see the gages better. They are old like me and the boat LOL... but they were both working and then just quit....went blank.

[yam911]

First I would suggest www.gaugesaver.com. They can make your gauges look brand new for not a whole lot of money.

[yam911]

If neither gauge is working I would first check the fuse(s) in the dual fuse harness. Highlighted in yellow in the illustration above. One fuse for both gauges. Your harness might just have one fuse.

If the fuse looks good I would disconnect the harness on the remote control side. Verify that you have battery power on the yellow wire terminal when the key is on. Verify you have a good ground on the black wire terminal.

On an aging boat sometimes you can get lucky by merely disconnecting the wire terminals and plugging them back together. All of them. Several times won't hurt. Look as the terminals to see what condition they are in.

I am also 74. I know about getting under the dash of a boat or under my car to change the oil. Getting back up is the hardest.

[Panama]

Thank you a lot. I will try to work on it some tomorrow and get back.

And you are right... getting out from under the console and getting back up is the hard part.

[Panama]

Thank you a lot. I will try to work on it some tomorrow and get back.

And you are right... getting out from under the console and getting back up is the hard part.

The red wire had power going to the fuse. The yellow wire did not have power going to the fuse. I pulled the panel with the control and shifter box apart and traced the yellow wire backwards toward the motor. I think I might have found the problem. The only thing is that when I pulled the yellow fuse holder apart, the metal end of the glass fuse came apart. But the yellow wire going to the fuse is not hot so the problem is elsewhere BEFORE the fuse. I am going to go het one of the old glass type tube fuses tomorrow morning....fix the connection up stream from it that I think is the problem and put the new fuse in and see.

It is hard to read but I think it is 10 Amp. I would think just a regular 10 Amp 12 volt glass tube type fuse is what I need right??? It is so old that it is hard to read.

You and the wiring diagram have really helped me understand the system and I could not be doing this without you. I really really appreciate the help. Thank you.

[Panama]

Big thanks to Yam911... you really helped me a lot. Without help and the wiring diagram. I would not have been able to fix it. My gages work now

When I did not have power on the incoming side of the yellow wire, I started tracing it back towards the motor. In the section between the shifter and the motor I found the yellow wire broken. There is evidence that a mouse has been around that area. I think he ate the wire into. I spliced the wire. Bought some new fuses, and fixed it.. Thank you.

I did have one question. The red wire... what does it do?? It looks like the yellow wire goes to the tach and the red wire goes to the speedo...but the yellow wire was broken ... the red wire was hot but the speedo still did not light up... just curious.

[yam911]

The yellow wire is for stuff that needs to have power when the key is on.

The red wire is for stuff that needs constant battery power. Some devices need a small amount of current to retain a memory.

Glad that you found your problem.