Tachometer needle broken - help

Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,037
Hunter 310 West Vancouver, B.C.
You're off to the races at 127 pulses/rev.

I don't think you need to worry about losing any memory when the battery is disconnected. It looks like only "nice to have" features such as TRIP HOURS and maybe CLOCK are volatile memory. I would THINK (hope) most of the important configuration stuff has a permanent memory.

The plug connections show pin #1 with an uninterruptable 12V supply wired directly to your battery (+) with an in line fuse. Don't bother if you don't care about the "nice to haves". Connecting #1 to the upstream side of the ignition key is good enough.

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smokey73

smokey73

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Oct 26, 2010
2,023
Hunter 40.5 Beaufort, SC
I hope so too. I really don't care about the clock, trip clock or even the hour meter. I have a Hobbs hour meter so don't need an electronic version and the other "nice to have stuff" is unimportant to me. Now that I have the pulse value to use (and possibly tweak based on the actual reading vs displayed) I feel I can move on reasonably well. I'll try it with the always on 12 volt not connected and see if it works for the tach function. If not I'll find a hot lead and tap into that.
 
smokey73

smokey73

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Oct 26, 2010
2,023
Hunter 40.5 Beaufort, SC
Ralph Johnstone said:
I don't think you need to worry about losing any memory when the battery is disconnected. It looks like only "nice to have" features such as TRIP HOURS and maybe CLOCK are volatile memory. I would THINK (hope) most of the important configuration stuff has a permanent memory.

The plug connections show pin #1 with an uninterruptable 12V supply wired directly to your battery (+) with an in line fuse. Don't bother if you don't care about the "nice to haves". Connecting #1 to the upstream side of the ignition key is good enough.
Click to expand
Finally got the tach wired up and calibrated against a direct reading optical rpm reader. Even though the actual number of teeth is 127, I tweeked the pulse setting to 129 to get the tach indicated rpm to match the optical reading.

It turns out that Pin 1 on the 8 pin connection does have to be connected to a 12 volt power source for the tach to work however, it does not have to be an "always live" source if you don't care about the "nice to have stuff" like you mentioned @Ralph Johnstone. I have connected it on the "ignition switched" 12V line so it is not always energized. The tach works fine that way and I don't like to have an always live source hooked up. Thanks all for the help everyone.
 
smokey73

smokey73

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Oct 26, 2010
2,023
Hunter 40.5 Beaufort, SC
@Ralph Johnstone Guess it is not solved. When I hooked it up to power both the "switched pin 4" 12V circuit and the "live I pin 1" 12 V circuit yesterday the tach worked perfectly (didn' worry about extra stuff). Today when I went back to move the boat from the mooring to the pier the tach did not register at all. Not sure what happened. I guess it is possible I disconnected something when I put the panel back in. I'll check it as soon as I can and feed back.

I guess it is not the end of the world if I have to have the live 12 volt line connected as it will have its own fuse and probably is like the background load from the presets on a radio.
 
smokey73

smokey73

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Oct 26, 2010
2,023
Hunter 40.5 Beaufort, SC
@Ralph Johnstone or anyone else for that matter. They show a fuse but do not provide one and don't say what size fuse to use. Any suggestions? I'm thinking maybe a 3 amp quick blow fuse? Can't really see any need for larger and could maybe even go lower. I guess I could see what they use for my radio live feed for the radio presets?
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,037
Hunter 310 West Vancouver, B.C.
smokey73 said:
They show a fuse but do not provide one and don't say what size fuse to use. Any suggestions?
Click to expand
Looks like they're only after wiring protection with a 5A fuse. The tach only draws 175 mA.

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Can't see why it wouldn't work on the downstream side of the ignition switch.,
 
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smokey73

smokey73

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Oct 26, 2010
2,023
Hunter 40.5 Beaufort, SC
@Ralph Johnstone GOOD NEWS. One of my connections was loose and when I put the engine panel back in, it became disconnected. It was the 12V live connection and it shows that you need this 12V connection for the tach to work, but it does not need to be unswitched. I have it hooked up as switched 12V so it does not get power when the ignition switch is off or when I turn the Starter Battery switch off. I am fine with that as the only thing I care about on the display is the RPMs displayed by the tach. Thanks for your help. Sorry I didn't see the F1 note. I'm planning on using a 3A quick blow fuse.
 
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