Replacement diode for Snapper charging circuit?

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  #1  
Old 05-02-11, 11:53 AM
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Replacement diode for Snapper charging circuit?

(Argh!) Accidently drew spark putting battery in backwards (poorly marked)

I'm hoping my Snapper charging circuit diode needs replacing, not the more expensive windings. (Fuse is ok.

Before cutting the shrink tube off of it, where can I buy a replacement.
Snapper only shows an entire section of wire harness not the discrete diode.

How many amps does it carry? Breakdown voltage spec?
I have access to high power diodes for transmitter power supplies - hoping to use one of those.
 
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Old 05-02-11, 07:10 PM
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Have you checked to be sure it is blown? If it was a short moment, it may not have toasted it. If it did, just grab one of comparable size from radio shack for a few bucks and put it in. The amp rating is going to be less than 20 amps. It's just a cheap run of the mill diode... don't have specs on it, but if you get one the same physical size or a little larger, it should be fine.
 
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Old 05-03-11, 12:44 AM
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Thanks, Cheese.
What about my 17.0 to 17.3 VDC readings across the battery during fast idle? It began about 14V or so and just climbed steadily like it would never stop. (Finally did at 17.3V)
 
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Old 05-04-11, 12:17 AM
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That's a pretty high reading I think, but the diode won't change that. The diode is what converts the A/C current produced by the alternator to the D/C current needed by your battery, and it prevents the alternator from getting burned up by backfeeding power when the mower is shut off. What voltage do you get from the red alternator wire with the engine running and the wire disconnected? If the diode is blown open, you won't get any charging at all. If the diode is shorted, the charging stator will begin smoking as soon as you shut the mower off.

When you say fast idle, do you mean full throttle?
 
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Old 05-04-11, 12:19 PM
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Most recent tests

Battery reads 12.61v (engine off) after driving 100 ft. from shed to garage.
Resistance check of diode = 520 ohms fwd, Infinity in reverse. (Normal diode?)

16.68 Vdc when running - measured from disconnected plug end (cathode?) to engine ground.

Guess that points to the Interlock Module?
 
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Old 05-04-11, 05:34 PM
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No, the interlock module has nothing to do with the charging. I'd say your alternator is working and the diode is fine. The charging voltage is a bit high for normal. I don't know if it's high enough to shorten the battery life or not, but if it has worked fine like this before, then it should continue to work fine. Connecting the battery backwards wouldn't have caused high voltage on charge.
 
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Old 05-04-11, 05:55 PM
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OK, Cheese.Thanks!
Is it possible the 17.3VDC my Fluke 77 DVM reads across the battery while it's charging reads high due to the AC component i.e pulsed DC? I'll look at the pulse train tomorrow on my 'scope and figure the charging voltage from there.
At the moment the Snapper is working without the Interlock Module. B&S only mentions minimum 14V(AC) charging.
I'll check the battery now and then to be sure it doesn't overheat. Will put the Module back in tomorrow.
I'll see if the local Snapper dealer will tell me what typical charging voltage is. (And report back)
 

Last edited by calrec; 05-04-11 at 06:38 PM. Reason: to add information
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Old 05-05-11, 12:34 PM
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Snapper charging voltage issue

Cheese, With the Interlock Module out, charging voltage is still 16+ to 17v.
Compared analog meter with DVM, their readings seem to track.

Read elsewhere someone plans to put in an LM338 adjustable voltage regulator.
that's a 'down the road' possibility - don't want to destroy the battery.
 
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