BF 130 - Tachometer problem

Of the twin BF 130 Hondas, the port tachometer is erratic whereas the stb is fine. Can I switch the leads on the "signal" post from one tach to the other to troubleshoot the problem?

Just switching the lead over might work ok, but depending on how you have the batteries connected, it might give you a false reading, thus screwing up your test.

First, I would rotate the selector switch on the back of the tach back and forth several times. Sometimes the contacts inside get dirty and that helps to clean them off and stops the erratic behavior. Then your problem is solved.

If that does not solve the problem then it would be best to just disconnect the one tach completely and try it in the other circuit. On the tach in the circuit that you are moving it to, just disconnect the signal lead and switch it. You can jumper the 12v and ground so it has the same references as the engine that you are running in the test. Do not put two signal leads on one tach...that could mess up your test.

Mike

Hi
Hi probably not related but I needs some advise on my Johnson 115 black and white series, after its last service the rev counter has to reading while on the go it stays at 3500 (at the 12 o clock position) and when off it sits at the 6 o clock position how would I fix this?

That "fix" of rotating the selector switch on the back of an erratic tach works well, and is endorsed by a number of manufacturers. I recall at one time, I actually found that fix in one of their FAQ sections.

Just 2 tips to add:
(a) Remember what setting the switch is on before you rotate it!
(b) On some tachs, you need to push in slightly with a small screwdriver as you rotate, as there are small plastic ridges that prevent the selector from moving.

When I played keyboards in a band, with amps powered off, we would rotate the switches ("pots" or potentiometers) though their entire range several times. This cleaned the contacts and prevented glitches when adjusting treble or volumes at HIGH volumes.

That's what you're doing when rotating the selector switch -- cleaning the contacts.

Old No7

I did the same thing (in the old days as Old No7) and still do today on my 60's Fender amp to clean the pots. Just too lazy to change them out.

Old No7 is right, the manufactures do have info on tach trouble shooting. Here is the one from teleflex.

http://www.jamestowndistributors.com/userportal/document.do?docId=837&title=Teleflex+Troubleshooting+Tachometer+Gauges

You will have to skip over the part on diesel engines.

And one from Faria http://faria-instruments.com/site_manuals/IS0100_Tachometers.pdf

Mike

Problem Solved!

Thanks Mike,

After rotating the selector switch as you suggested I disconnected all the wires and in the process the hot lead ring terminal came off. It was a bad crimp held on with shrink tube. Put on a new ring terminal the tach works fine!

However, the tach has a couple of extra wires on it not mentioned in the Faria "Installation Instructions". They are small, maybe 22 ga. on the signal and ground terminals. I don't know which electronics applications uses the tach signals, but I have a fish finder, radar, autopilot, chart plotter and VHF. Anybody have ideas on this?

By the way the Faria trouble shooting guide says about erratic tachs..."This symptom is caused 99% of the time by an intermittent connection between the wire and the ring or spade connector". They were right this time.

Isn't it nice when the answer to the problem is simple...and cheap?

There is nothing else that I know of that uses the tach signal. Could it have been attached to the battery (ignition) terminal and ground? Or possibly between the connection for the light lead and the ground.

If battery and ground, then it might go to something like a digital depth finder or some simple device that is activated when the ignition is on.

If you have a compass, it could be the compass light. Normally, they are tapped into the light lead, but someone may have chosen to do differently.

Looks like it is time to trace it out and see where it goes.

Mike

I know this is an older thread but just wanted to put this out there as it might help someone experiencing a tach showing much higher RPM's at idle and all through all ranges. I could tell the engine was NOT revving at 2200 at idle, it was running as well as it ever was. Reading somewhere that the tach is tied to charging rate I checked output across battery terminals even though Charging guage showed a normal 14V but battery was getting charged at over 18! I checked meter for accuracy on my pickup and verified it was working. After looking through Honda Service Manual it states if charging voltage is over 16V replace the IC Regualtor on back of alternator, which I ordered and installed. Tach was still reading high but charging voltage seemed normal at 14.5V but as engine continued running charging voltage rose steadily up into the 17V range. I obviously shut everything down. Then I came across this thread, well after checking all the grounds (which were fine) I swept dial on back of tach after noting original position. Well, I don't know how but that was IT, all is back to normal. Thanks for all the info Hondadude!