Tachometer problem

Fairbro · Posted: Mon Sep 10, 2007 10:23 am Post subject: Tachometer problem

One of my Honda tachs has stopped working. It started by bouncing between 0 and whatever, and then worked OK for a few minutes, then quit altogether, then repeat. Now it's new trick is to bounce from o to about 2000 on the down side of a high rev., but mostly it just doesn't work at all. I have checked as many wires and connectons that I can get at (both at the back of the tach, at the throttle and at the motor) to no avail. Does this sound like wiring or a bad tach to anyone? Thanks for any advice, Gary

C-WEED · Posted: Mon Sep 10, 2007 10:26 am Post subject:

Now here is an advantage of twins I never thought about Laughing

Swap out with the other tach for a quick troubleshoot. There is an adjuster on the back that some have reported can cause your problem. Corrosion on the adjuster If I remember. If not that it probably is bad.

Fairbro · Posted: Mon Sep 10, 2007 10:39 am Post subject:

Thanks for the quick response. I guess I could do that but I hesitant to cut any wires except to replace a bad gauge. The pigtail off the back of the tach has rubber coated splices that look like they don't come apart. Do they???

C-WEED · Posted: Tue Sep 11, 2007 2:48 am Post subject:

Did you see the adjuster screw/switch? Some folks have sprayed it with electrical contact cleaner and switched it back and fourth to clean the contact connections. The adjustment is used to set the instrument for 4 or 6 cylinder engines. Be sure to put it back on the original setting. I think I recall one guys tach just got bumped off the correct setting and a simple reset got the tach working normal again.

I don't have a Honda so I can't check: But the black you describe sounds like plastic shrink wrap. A small tube put over wire connections and heated. The tube shrinks tight around the wire when heated for a good protective seal.

I know how you feel about not wanting to alter the original wires. You could take it to a repair place and pays some one else $80 to cut those wires. Or give yourself enough wire to work with and snip, snip. Maybe use part of the $80 you saved on a nice soldering gun if you don't own one for the resplicing.

Fairbro · Posted: Sun Oct 28, 2007 10:09 am Post subject:

update on Tach problem. As with many mysterious problems that occur at the same time but do not appear related, mine are apparently related. I took Minnie up to the boat tech today and the rectifier on the/in the alternator is bad causing the low battery problem and the tachometer problem. He advised me that a less than extremely tight ground connection or an even momentary mismatch hook up could have caused the failure. He told me to get rid of the battery post wing nuts because they give the impression that finger tight is good enough. Everybody in the world except me knew this, right? Anyhoo, anyone with a bouncy tachometer would do well to check all battery connections. Having one tach out I did come up with a way to syncronise the motors though. Look back and out at the crown of wake between the motors. Center good, off side bad. Hillbilly tachometer! Also, I did verify that the tach was good by hooking up to the other one's leads. Good advice since electrical parts aren't returnable and I doubt I'll be adding a third motor. Thanks for the help! G.

Dora~Jean · Posted: Sun Oct 28, 2007 11:55 am Post subject:

Good info on the wing nuts. I USE wing nuts though, always tighten with pliers to cinch them up though. I also use a couple of stout external tooth washers between some of the lugs and the nut to provide a better electrical connection. You can get SS 5/16" and 3/8" ext tooth washers at True Value hardware stores, at least here in Simi.

Fairbro · Posted: Wed Dec 12, 2007 11:06 am Post subject:

Here is my solution to the intermittant bouncy/dead tachometer. Swapped out tachs ( non working one plugged into working one's leads)to prove that was not the problem. NOT the problem.
Checked wiring inside throttle control. Tachometer wires just enter the control and then exit with no connectors or other potential problems. No reason to check throttle control box for any tach problems.
Replaced rectifier ($137.00) because it was easy to get at and I was told by several techs that 9 out of 10 times that is the problem. NOT the problem!
Had mechanic replace the charging coils ($160.00) under the fly wheel and that of course was the last place I wanted to go but alas where the problem was. One coil was visibly burned and cracked. We speculate that everything was caused by a simple loose ground to battery connection.
CHECK THOSE BATTERY CONNECTIONS OFTEN FOLKS!

Papillon · Posted: Wed Dec 12, 2007 7:30 pm Post subject:

I have a bouncy tachometer as well...it must be catching. I took a look at my battery connections and I see I need to get out the tool box and emory cloth. Your post may have saved this C-Brat and others some good Santa money.