tach problem

Evinrude 40 hp 1992 10 pole alternator. Original tach has died and replacing it with a Teleflex 61278. Problem: New tach not working. Set at 5p per instructions and checked AC voltage at the tach terminals. 9.8vac ( between send and ground terminal) at idle and voltage ramps up when increasing throttle. DC voltage is 12.5 between IGN & GRND. Tach needle drifts up to about 100 at rest (key off ) then goes to zero when ignition switch is turned on. Ran jumper wires from engine tach terminal to the tach itself and also ran ground jumper from negative of battery to the GND on the tach. AC voltage reading is the same as mentioned above and ramps up when throttle is advanced.
Wondering if new tach could be bad????

Re: tach problem

Not to take anything away from the forum, but in my opinion Teleflex has the best technical support group in the business and they are almost always the best help - reach them by email here:

http://www.teleflexmarine.com/cgi-bin/page.cgi?site=gauges&type=us&page=1012

Re: tach problem

Thanks........I've been in touch with their technical support, and they suggested I had purchased a faulty tach. I returned it to the place I had purchassed it and have since received another identical unit (also from the same boat shop). It too is not working. I read the thread about bypassing the rectifier and jumping the alternator yellow/ grey to the grey tack lead. It made no difference....the tach still doesn't work. I will call them in the morning. Maybe they had a bunch of bad units from the same batch and I just got caught up in it. Anyway...thanks for the info.

Re: tach problem

Just to let all of you know..........I was moving some of the terminal block wiring in order to see behind the rectifier block. Down at the very bottom there is a 7/16" bolt. It is hard to see and in my opinion it is impossible to reach with a standard socket. Just under the head of that bolt I found a wire ring terminal lug and the broken end of the connector wire. This is the ground lug for the rectifier and evidently it was what was causing all the trouble. I made the repair and now all is working fine. It just goes to show that something as simple as that can really get a person's head spinning.
Thanks for the help.