1982 johnson 115 charging/no tach

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paul bacon

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well i got a 1982 johnson 115, and recently the tach quit working, i used a meter to check everything thing, there is a good ground, good power, and the pulse wire seems to be getting a signal from the motor according to my volt meter. so next i checked the voltage at my battery which was 12.50 volts and then when its running its at 12.45 volts, is that normal? is the rectifier starting to go and thats why the tach quit? seems to me that when the motor is running it should be charging somewhere around 13.50 volts.
 
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baiwan

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Re: 1982 johnson 115 charging/no tach

paul bacon said:
well i got a 1982 johnson 115, and recently the tach quit working, i used a meter to check everything thing, there is a good ground, good power, and the pulse wire seems to be getting a signal from the motor according to my volt meter. so next i checked the voltage at my battery which was 12.50 volts and then when its running its at 12.45 volts, is that normal? is the rectifier starting to go and thats why the tach quit? seems to me that when the motor is running it should be charging somewhere around 13.50 volts.
Click to expand...
Change rectifier, then check regulator.
 
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paul bacon

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Re: 1982 johnson 115 charging/no tach

i talked to a mechanic today and he seems to think my charging system is working fine, he thinks the tach is bad. so i guess ill have to figure out a way to test the tach first and then maybe think of doing the rectifier.
 
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emdsapmgr

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Re: 1982 johnson 115 charging/no tach

The 82 has a rectifier only. As such, the charging voltage is unregulated. When running, the rectifier will permit volts to gradually creep up as the battery charges. It should creep up to as much as 15+ volts after running for 30-45 minutes-if the rectifier is working normally. Your volt gauge is showing normal battery voltage, so the rectifier is a prime suspect in your problem. Odds are that the rectifiers fail more than tachs.
 
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cdoliver

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Re: 1982 johnson 115 charging/no tach

you can have a bad rectifier and still be charging. Does your tach "zero" when you turn the key on?
 
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baiwan

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Re: 1982 johnson 115 charging/no tach

If your figures are correct, the charging system isn't working.
12.50 - engine still and 12.45 when engine running.
Who told you that charging is ok with these readings? Omit him next time.
Did you change rectifier?
 
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paul bacon

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May 27, 2009
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Re: 1982 johnson 115 charging/no tach

yea my tach just zeros when i turn the key on and thats all it does, i just dont understand, i have good power, a good ground, and i checked the pulse wire with a meter and i am getting a signal at the tach, is it just too weak of a signal cause the rectifier is starting to fail??
 
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paul bacon

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Re: 1982 johnson 115 charging/no tach

oh and is the rectifier under the flywheel, or does this motor have it on the side?
 
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cdoliver

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Re: 1982 johnson 115 charging/no tach

the rectifier is round with three wires coming off of it, red and yellow ones. You didn't happen to change your batteries anytime recently and maybe hook the cables up backward for a second?
 
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paul bacon

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May 27, 2009
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Re: 1982 johnson 115 charging/no tach

no the batteries were never hooked up wrong, i guess ill try the rectifier. easy to do so i might as well, ill let you know what happens
 
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