Tachometer Wiring

[Pickels]

My Mark78A Engine has the tach wire's disconnected. It is a two terminal Faria Tachometer. I think one wire goes to ground - and the other goes to the ballast resistor. <br /><br />BUT - which side of the resistor? One side of the ballast resistor goes to the distributor and the other goes to a terminal post on the coil.<br /><br />My bet is it goes to the coil side.<br /><br />And finally - the ground side -- do I just ground it to the engine block?<br /><br />Thank's in advance -- <br /><br />Happy Labor Day Weekend

 

[Pickels]

Re: Tachometer Wiring

Just did a closer look at the wire ends that were taped off. Seems that there are two wires coming from the tach - and they both have a wire connector on them that is round. The wire conveniently ends right beside the two coils on the engine -- and they look as if they would both connect to the two electric posts on the coil? Would this be a correct assumption?

 

[Laddies]

Re: Tachometer Wiring

It really depends on the tach, but most of the old 2 terminal one went to ground and one to the - side or pt side of the coil

 

[Pickels]

Re: Tachometer Wiring

Ok -- all I have done is thought about this all day.<br /><br />First -- there are two gauges on one set of wires.<br /><br />The temp guage is marked + and -<br /><br />The minus goes to a sensor on the engine<br />The plus goes to one of the two posts on the tach.<br /><br />Assumption: 12v passes into temp guage and out to ground via the sensor. That means that one of the wires on the tach is probably a 12v post. If that is correct - can I get the 12v off of the + post on the ignition coil?<br /><br />If yes - then would it not be logical that the other post on the tach goes to the negative post on the same ignition coil?<br /><br />It appears that there is no ground on the tach - there is no post for it and no appearance that there ever was one attached.

 

[hullofalottatrouble]

Re: Tachometer Wiring

ahrmles<br /><br />on my old 2 terminal tach.. <br /><br />one wire post- marked - snd - went to negative terminal on coil<br /><br />other wire post - gnd - was tied into over gauges ground wire.. <br /><br />there was no 12v ignition post on my old tach.. apparently that is common for old tachs..<br /><br />my new tach has 3 posts<br /><br />12v ignition - ties into same 12v ign wire that makes all my other gauges function when i turn the ignition key<br />snd - goes to coil<br />gnd - ground

 

[Laddies]

Re: Tachometer Wiring

The only need for 12v on early mercury tachs was ot run the light if so equiped, the tach worked of the pulse of the coil