Tachometer help...

[Sotech]

Hello I'm new to the forum and I am really hoping that you can help me. I've asked this question on another site and was unable to get any kind of help. I have a tachometer that I am trying to fix but it is a little different that other types of tachometers. It doesn't take the normal +12v/Gnd/Signal. I've heard these boat tachometers work a little different than vehicle tachometers. If there is any information that you can give me I would greatly appreciate it. Here is a link to some photos of the tach.


http://www.flickr.com/photos/20166103@N05/sets/72157606877440549/

Thank you for help in advance. I really can use any help that you can give.

 

[Silvertip]

Re: Tachometer help...

It doesn't matter what kind of tach it is, it still requires +12V, ground, and a signal line to work. The inputs may be labeled differently but they are still +12V ground and signal. Auto tachs are different than tachs for outboards. Auto tachs have a signal input that count the number of pulses from the ignition which is dependent on the number of cylinders the engine has. Outboard tachs are driven by a signal from the charging system and is based on the number of poles on the stator. A 12 pole stator will produce 6 pulses and is not dependent on the number cylinders the engine has.

 

[Sotech]

Re: Tachometer help...

Yeah I understand that almost all tachs and any electronics for the matter require 12v/Gnd/Sig. But honestly I don't see how its done on this piece. The picture shows 3 inputs but only 2 are fuctional. 1 of the inputs I can assume is just there to hold the insides in place. If you follow the inputs 2 actually lead to the circuit board. So seeing that you would think that ground would be the case since alot of older electronics use the casing as Gnd. But there is nothing that connects the circuit to ground. The guy that asked me to look at this told me that it should work with gnd and signal only. I have never seen a gauge that works this way. *shrug* I just stumped. Thanks for the reply though I appreciate it.

 

[Silvertip]

Re: Tachometer help...

Your age is showing!! Lots of older tachs used to work that way. Signal and ground is all you need if the third terminal is just a mounting device.