Coil, Resistor Wire Problem

[tinytanic1]

I have a 1977 120hp Mercruiser. Problem is the coil gets incredibly HOT. I've replaced the resistor wire and coil (along with ign. parts i.e. plugs, points, etc.). I've doublechecked all my wiring throughout engine and control panel accouding to wiring schematics in 140hp service manual. Everything checks out except. I'm getting Battery voltage at '+' end of coil. Should'nt voltage be reduced after going through resistor wire????? I also disconnected the start assist wire leading from starter to coil with same results.
The new resistor wire checks out with 1.5ohms, which is a little less than manual says (1.8ohms), but should still see voltage drop, right?????
I've also replaced ign. switch, solenoid (not solenoid on top of starter, the other 4 post solenoid). I don't have any other ideas???????

 

[Reel Poor]

Re: Coil, Resistor Wire Problem

(1) What is the voltage at the battery with the engine running?

(2) What is the voltage at the alternator BATT terminal with the engine running?

 

[alaska_av8r]

Re: Coil, Resistor Wire Problem

There are others on here that have tons more knowledge on this than I do, but on my coil I had two wires to the positive side. One wire had 12V when starting the engine and after the engine was running the resistor wire showed 9 volts with the other one showing 0 volts........

Both wires were attached to the coil with a single connector and I separated them to check them, probably didn't have to.

So if yours is similar wiring, I assume either:
....your resister wire is messed up or...
....you are still getting 12 volts thru ignition when you aren't supposed to

as how to fix it.....better wait for the pros to chime in

 

[Snoopywoopy]

Re: Coil, Resistor Wire Problem

You might also check that the ammeter (if one is installed) is connected via a shunt and not directly to the meter. This can cause a problem with output from the alternator not being properly regulated and output voltage being too high.

Real and AV8R are barking up the right tree as well. This sounds like you're getting more than 9V to the coil when running.

 

[wire2]

Re: Coil, Resistor Wire Problem

You didn't say if the engine was running when you took the voltage readings. If not, and the points were open, you would read battery voltage at the coil + terminal. It's an open circuit, so there's no voltage drop across a resistor.

During Start, you should have battery voltage at +.
At Run, a wire from Ign should go through the resistor to +, showing reduced voltage.

One caveat; there can be no direct connection between the Start lead and Ign, or the starter will continue to run.

 

[ljbarry]

Re: Coil, Resistor Wire Problem

I maybe having the same problem. When and where should i be getting 9 volts? I have only got 12+. Where is the resistor?

 

[tinytanic1]

Re: Coil, Resistor Wire Problem

SNOOP.....What is a shunt and where should it be? I just have a one wire alternator. I'm pretty sure the Alt. is inline directly with ammeter. Could this be why I'm gett battery voltage in run positon. If so, where do I get a 'shunt' and how do I install it??????????