Tachometer Question

[adam24601]

Hi..I have a 22' Sunrunner 1988. The engine is a Merc 5.7 V8 with thunderbolt ignition. I/O.<br /><br />My tach has been erratic. Yesterday when I turned on the motor, the tach would rise all the way to the right and sit there. I'm not sure where the wires are..but I found a wire that was hooked to the coil. I believe it was a reddish grey maybe..then a black wire..not hooked to anything. Does this sound like these are the tach wires..and if so...is the black ground? Could that be causing the tach to not read? Help please...<br /><br />Adam

 

[Elk Chaser]

Re: Tachometer Question

Normally on the back of tach there should be 4 wires, start there with obtaining your wire colors.<br /><br />Usually there is a; <br /><br />Red that goes to a switched (igition switch) 12 volt power supply.<br /><br />Black that goes to ground<br /><br />Green to Trigger this goes to either the negative side of coil or tach output terminal on an aftermarket ignition control module.<br /><br />White or Yellow to the lighting circuit that is switched usually on the dash for dash lights.<br /><br /><br />If the Black or Green (your wire colors may be different) are not connected properly or loose the tach will not work properly.