Tach Question?? Won't zero at pwr up

[Pst76]

Have a 85 470 Mercruiser in a 19ft Four Winns cuddy. Have been restoring boat all summer and now gotten to finalizing a few items. <br /><br />The tach is not working and I believe may just be bad. <br />Before I replace wanted to ask for second opinion.<br /><br /> Symtom is when I switch the key on Tach needle goes up instead of zeroing out. I checked wires and looks to be hooked up correctly unless somthing in the harness is wrong. <br />Is there a polarity issue or somthing reversed or could it just be a faulty tach?<br /><br />Thanks for any feed back

 

[KRS]

Re: Tach Question?? Won't zero at pwr up

Define for us what "goes up" means? goes from below -0- reading to 1 or so? or halfway or redlines? Does it work once boat is running?

 

[Pst76]

Re: Tach Question?? Won't zero at pwr up

With no power to Tach I have a zero reading. As I turn ignition switch on/only. Needle goes up to approx 800rpm mark and stays there. <br /><br />When engine is started I get no change. Stays at 800 rpm. No reaction on tach regardless of engine rpm change. Shut everything down and gauge goes back to Zero.

 

[tommays]

Re: Tach Question?? Won't zero at pwr up

http://www.tflx.com/tech.html <br /><br />everything you need to test everything<br /><br /><br />tommays

 

[Pst76]

Re: Tach Question?? Won't zero at pwr up

Thanks tommays. great info. will test tonight. Break out the clip leads....