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bad switchbox

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bone9999

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I have a 82 merc. 40 hp which was just diagnosed with a faulty switchbox by CDI's tech support. This was a brand new switch box which was replaced no more than a month ago due to a weak spark and voltage output issues.

My question is - Would a very small amount of voltage on the kill switch wire cause the switch box to short?

I am showing ~0.2 volts on my kill switch wire (black/yellow) while disconnected from the switch box and key is in the on position. In the off position i get 0 volts and the wire shows grounded as it should. Tech support guy didnt think that was enough to kill the pack but i am running out of ideas as to why this has happened so quickly.

For the record the trigger, stator, both coils and rectifier have all tested within spec for resistance and voltage.
 
No, there is always (some) continuity in the kill circuit, so that is definately not the issue.

If this is an electric start model or you have it set-up to charge a battery I would take another look at the rectifier, more specifically the wiring leading from it. If the rectifier has nowhere to send it's power (short in one of the wires, no battery connected, loose connection to the starter etc) the power that it generates (converts AC from the stator to DC) will "back up" into the ignition components.

Most often it will take out the stator "first", but it could be the cause of multiple switchbox failures as well.

If everything looks to be ok you can still disconnect the stator feeds to the rectifier and isolate them, then run with the rectifier disconnected and see if the switchbox survives. If it doesn't, regardless of what your tests show, you would then be safe changing the stator which is the most likely culprit...
 
Thanks for the info galamb!
I had my doubts about the kill switch, but wanted another opinion.

As silly as it sounds i actually replaced the switchbox, tested everything out and then went about replacing some old brittle wiring in the motor. Im thinking maybe one of the old wires was the cause for the old and replacement box to go out. Should have taken my time and replaced all the old crap before testing the new. Glad i bought the CDI with a warranty.

Everything on the motor (except the box) seems to be in order - correct voltages and no grounding issues. The first time i fire it up, as soon as the new switchbox gets here, i will try isolating the rectifier.

Thanks again for your help
 
Hello, haventaclue. I have actually already tested the rectifier in that manner, but thanks for the input. I am really hoping it was just one of the old wires that i replaced, some were in pretty bad shape.

Dont know if this is a meaningfull test but I also checked the voltage on the DC pole of the rectifier while running and noticed no significant spikes, stayed ~13v. I am assuming this is good, never had an issue with the battery charging.
 
bone9999 said:
I have a 82 merc. 40 hp which was just diagnosed with a faulty switchbox by CDI's tech support. This was a brand new switch box which was replaced no more than a month ago due to a weak spark and voltage output issues.

My question is - Would a very small amount of voltage on the kill switch wire cause the switch box to short?

I am showing ~0.2 volts on my kill switch wire (black/yellow) while disconnected from the switch box and key is in the on position. In the off position i get 0 volts and the wire shows grounded as it should. Tech support guy didnt think that was enough to kill the pack but i am running out of ideas as to why this has happened so quickly.

For the record the trigger, stator, both coils and rectifier have all tested within spec for resistance and voltage.
Click to expand...

i have had problems with switchboxes with a 175 merc and there are times that even a new one will have problems. i found a place in Tulsa OK that i could get rebuilt ones but that was a few yrs ago look around for re-built one's in your area.
 
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