Tach problem driving me out of my mind!!

**Ron V** · 05-18-2003, 08:37 AM

Got a Faria (yikes) tach that is going bonkers. Drops off to zero, then comes back and goes up to 7500, then back to normal, dances all around. Had a friend who designs ignition systems for Motorola come and check the charging system thoroughly (even had a couple tricks up his sleeve that weren't in the manual), everything is perfect. Got 11 volts at the terminal board and 10 at the tach. Temp and trim gauges are powered in series through the tach harness and they work fine even when tach shuts off completely, so trouble must be in the gray signal wire?? Found that the plug wasn't quite shoved onto the receptacle on the control box all the way (wires were 1/4" too short!) and that the needle on the voltmeter danced when it was jiggled (jiggling it did NOT affect the tach while running though). Spliced in extra wire, pushed the plug on all the way, STILL got problems. Checked tach harness with a voltmeter to check for broken wires and found nothing.

Next I'll unplug the tach and check the female receptacle in the control box with a voltmeter while running down the lake to see if the trouble is in the box. If that checks out, I'll try a different tach. Anyone got any ideas of any other bases I can cover before buying a new gauge? Motor is a 1995 Evinrude 90 crossflow.

**Superdave** · 05-18-2003, 08:51 AM

Run a wire directly from the tach to the rectifier. If that works you have a bare wire inside the box. I've had one shorted and put the signal to the steering cable & wheel. OUCH!! Talk about good spark.

**Bill Rogers** · 05-18-2003, 07:14 PM

Superdave has a good idea. 1 volt drop is too much - there's hardly any load on the sender lead, so the voltage should be the same at either end. Could be a ground problem as well.

Ron, was your meter on DC or AC when you checked the "send" voltage?

**stvhelm** · 05-19-2003, 08:27 AM

Ron, your grey tach wire should be connected to 1 of 2 wires that come from the stator that go to the rectifier. the tach should work off either 1 of these 2 wires. try switching it to the other one. if the problem goes away then something is up with your stator.

**Sparkroost** · 05-19-2003, 07:59 PM

re-check your rectifier for a open connection to ground. If the rectifier is grounded through it's chassis, check it's ground.

**Ron V** · 05-20-2003, 08:34 AM

Thanks guys. I haven't had a chance to test it again yet but I'll let you know when I do.

**Gordie Miller** · 05-20-2003, 09:00 AM

the muffler bearings?

**Ron V** · 05-20-2003, 11:40 AM

Gordie,

I checked the muffler bearings over with a micrometer and they show +- .001" of spec. So I think they are passable. I'm starting to think it could be the spark plug wire gaskets, but can't say for sure.........