I have an '03 Honda Rancher 350 ES with less than 1000 miles on it. I went to start it recently and everything was dead - no digital display - nothing. I checked the fuses and the main was blown. Inserted the spare and it immediatley blew as well. I briefly shorted the fuse with a screwdriver and it started and ran great. Battery showed over 12 volts with a meter.

I inspected wires for a short but didn't find anything - at least not yet. I bought more fuses and popped one in. This time it didn't blow and started and ran great. I shut it down and 30 minutes later it was again completely dead. The fuse was not blown. Now the battery was reading about 8.5 volts obviously getting pulled down fast.

I removed the rectifier and jumped the battery and it starts and runs great. Then when I hook up the rectifier, it doesn't idle quite as smooth and the digital display starts wigging out a bit. Also the battery voltage seems to get pulled down even faster. I remove the rectifier and all is well again.

While it's running with the rectifier removed, I test the voltage at the battery leads and get less than 12 volts - whatever the battery has left.

My question is should the alternator be charging the system with the rectifier out? I think this is a stupid question because it may need the rectifier to charge the battery, but I just don't know for sure. Does all this indicate a bad rectifier? Where can I test the alternator output? I don't know where the outputs are located.

Thanks!

 

the rectifier is needed to charge the battery. The alternator does just that-creates "alternating current" (hence the word "alternator")

but the battery and electrical system is all DC current. The rectifier is basically a bunch of diodes or "one way valves" for electricity to convert this unusable AC current to DC current.

It sounds to me like you have a bad rectifier, but of course I can't tell you for sure. If you have a manual it may give you some tests to perform to find out for sure.

 

Quicksilver - Thanks very much.

Can someone tell me where the alternator outputs are where I can test with a meter?

 

I dont know about an '03 rancher, but i have a manual for an '04 (new body style, same thing though, i hope)
I'll walk you though the manual's tests. I hope your wire colors are the same.

First-with the bike shut off overnight, what's the battery voltage. If it's above 12 volts, you're ok. If it's low (like 10 or so) then you may have a bad battery (bring it to a shop and load test it) or you have a parasitic draw (a short or something staying turned on) or the battery needs charging. Since you had a blwon fuse, we'll skip this for now, I'll assume you have a good fully charged battery.

Ok, at the regulator/rectifier connector, 5 pin connector, you can test the alternator and the wiring to the rectifier.

the red wire should have battery voltage at all times (key on, key off, engine running, engine off, etc.) that means all the time. So at ANY time you dont have battery voltage there, then that's your problem. That fuse that blew out, that's what powers this wire.

The green wire, should be ground. measure continuity from this wire to the frame and engine block. Should have little or no resistance.

the 3 yellow wires are the 3 AC outputs of the alternator. Measure continuity from each of these wires to ground, should have NO continuity, meaning not shorted to ground. Also, Each wire should have some continuity to the other two, the spec is .1 to 1.0 Ohms.

 

I checked all the leads to the rectifier and they checked out exactly as you described. I did buy a new battery the other day because my old one wouldn't hold a charge, so I know it's good.

In the minute or so I had the new battery hooked up and made sure the ATV started, the rectifier got burning hot! I couldn't even touch it to disconnect it.

I'm getting a new rectifier and hopefully that will do it. Thanks for all the help.

 

Just to follow through on this. I bought a rectifier from an '05 Rancher on eBay for $25. I plugged it in and everything works great. The fuses don't blow. The battery doesn't drain, and the alternator is charging the battery when it's running.

Thanks Quicksilver for the excellent help!