Which side of Coil is negative?

[adam24601]

Hi, My tachometer was acting funny so I opened up the cover to the motor and found the black wire (I assume ground) disconnected. I hooked it up next to the positive wire..next terminal over..but it just pegged either the low or high end of the tach and stopped. Could there be two positives and two negatives on the coil? Maybe I hooked up to the positive? Any help would be greatly appreciated!<br /><br />Adam

 

[Blk-n-Blu]

Re: Which side of Coil is negative?

Adam, What motor and ignition set-up do you have

 

[adam24601]

Re: Which side of Coil is negative?

I have a Mercruiser 5.7litre V8 with Thunderbolt ignition. <br /><br />Adam

 

[adam24601]

Re: Which side of Coil is negative?

More Info: I am assuming the red wire is positive and I'm not even sure these two wires were for the tachometer. It was doing the same thing (going all the way to the low or high end) before I hooked the black wire to whatever I hooked it to. The terminal had four posts on it. I hooked the black one up to the post on the right closest to the front of the motor looking at the motor from inside the boat. I hope this makes sense.<br /><br />Adam

 

[adam24601]

Re: Which side of Coil is negative?

Sorry..more thoughts...could it be that the black wire if it is actually from the tach should not be hooked to the coil at all? The other wire which I believe was a red and black maybe..was already hooked to the coil. The other black wire..was disconnected from wherever it should have been. I just assumed to hook it back to the coil?<br /><br />Adam

 

[rattana]

Re: Which side of Coil is negative?

Adam the wire for the tach hooks up to the negative side of the coil.

 

[rattana]

Re: Which side of Coil is negative?

I just read your first post, yes there can be two wires on both the positive and negative sides of the coil. On the positive terminal, one wire is for power when cranking, the other is for power when running.(they are different voltages) For the negative terminal one goes to the distributor and another goes to the tach. It is possible (depending on your setup) to have a third wire on the negative terminal for the shift interrupter switch.