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Discussion Starter · #1 ·
An electrical ignoramus looking for help here...

I've installed the Honda 12V under-seat accessory socket, which is basically a plug-and-play installation. No wire stripping/soldering, etc. required, since the Honda accessory connects directly to the OP behind the battery. The Honda accessory socket harness includes a 3A in-line glass fuse :frown:

Time to verify it all works...
  • I connected a 12V-SAE adapter to the socket, Ignition on and indicator light on adaptor lights. Ignition off
  • I connected an SAE voltmeter/USB charger to the adapter. Ignition on: Indicator light flickers and 3A fuse blows. Ignition off

If I just connect the SAE voltmeter/USB charger to my direct/unswitched battery tender SAE lead (with its own 7.5A blade fuse) it works fine. However the point of the Honda accessory was to be able to use switched power, so I'm wondering where the problem might be.

  • Battery tender SAE lead (7.5A fuse) => SAE voltmeter/USB charger <<= this works fine, not switched
  • Bike switched harness fuse (7.5A) => OP connector => accessory harness fuse (3A) => SAE 12V adapter fuse (10A)* => SAE voltmeter/USB charger <<= 3A fuse blows when ignition switched on

* - I took the SAE 12V adapter apart to see if it's fuse was okay (it was); the voltmeter/USB charger can't be disassembled.

The voltmeter/USB charger is dual 5V/2.1A, so could draw 10.5W, which is less than 1A at 12V, so I wouldn't expect it to blow a 3A fuse.

What am I missing?
 

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1 amp at 12v = 12 watts.

Get something else to plug in to verify that what you added is fine.
I'm guessing a problem in the newly added wiring.
Fuses dont just blow for no reason!
AND dont put a bigger fuse in! IF its to be 3 amp leave at 3 amp!
 

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Discussion Starter · #3 ·
1 amp at 12v = 12 watts.

Get something else to plug in to verify that what you added is fine.
I'm guessing a problem in the newly added wiring.
Fuses dont just blow for no reason!
AND dont put a bigger fuse in! IF its to be 3 amp leave at 3 amp!
No worries on a bigger fuse, I know better than that. I actually dug a few 2A fuses out while troubleshooting this figuring I wasn't trying to draw anywhere near 36 watts.

I'd like to be able to verify whether this is an issue with the Honda accessory harness or what downstream of the harness caused the fuse to blow. The Honda accessory harness is basically pre-assembled with a Sumitomo connector on one end and a 12V "cigarette lighter" socket on the other. All you do is connect the harness to the bike's option plug, bolt the socket to the rear sub frame, and use a few zip ties to route the harness wiring.

Today I picked up some more 3A in-line fuses and a simple USB 12V charger (i.e. no SAE adaptor or wires) and that seems to work just fine to charge my cell phone. So I'm guessing one of the pieces of the SAE chain I tried to put in place caused the problem and the OEM harness is okay. I'd like to be able to use switched power for heated gear as the temperatures fall, but would rather not be frying stuff trying to hook it up.

I've always run heated gear (e.g. glove liners or a jacket through a rheostat) off the battery tender SAE connector (these always have their own 7.5A fuse) in the past without problems, but like the idea of using switched power to do this if I can.
 

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There is obviously something shorting out to ground. Instead of repeatedly blowing fuses, put a bulb across the fuse terminals, that will light up brightly when the short is present dimly when there is a normal load, and not at all when there’s nothing connected.
 
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Discussion Starter · #5 ·
There is obviously something shorting out to ground. Instead of repeatedly blowing fuses, put a bulb across the fuse terminals, that will light up brightly when the short is present dimly when there is a normal load, and not at all when there’s nothing connected.
Thanks! I'll give that a try.
 
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