Help! hooked up jumper cable backward!! duh

[lestro]

Ok!! I had a dead battery on my xb12r so I hooked up the jumper cables (backwards) Now the key switch fuse keeps blowing instantly. Anybody know what I blew up?? [confused]

 

[climberfreak]

keeps blowing when you go to start it or when you try to jump it?

 

[lestro]

it blows as soon as you replace it.

 

[Buellysses]

I believe there is a diode in the fusebox. I would replace that.

Extreme reverse current probly took that out.

 

[climberfreak]

and thats the only one that blows? check the wires that lead to the box maybe a sodder broke loose and is shorting out

 

[lestro]

I did check the diode with a meter and it looked like a diode should.

 

[dave_xb12r]

This may be dumb, but how should a diode actually look on a meter

 

[lestro]

using an ohmmeter on resistance scale, low resistance one direction, and reverse leads, get high resistance, if it was shorted it should be low resistance both ways

 

[Buellysses]

most decent meters will have a diode check function. measures the voltage drop across the diode. Will be infinity in one direction and .7 (or .5) volts in the other.

If the Diode checks out alright I would start by unplugging the ECM and seeing if the fuse blows. Hopefully you didn't toast that.

My next stop would be the gauge cluster. Maybe the bank angle sensor. Trying to think of anything else that may have solid state electronics in it... reverse polarity on a battery generally wont affect switches, relays, or stuff of that sort.

Just start unplugging stuff till the fuse quits blowing... =)

 

[climberfreak]

trail and error my friend just go buy you a box of fuses and have at it

 

[Buellysses]

1.) Shove a penny in the fuse hole.
2.) Look for smoke.
3.) Problem identified.

(I will personally come club anyone over the head who actually tries this.)

 

[lestro]

Thanks fo all the hints, I'll give it a shot, except for the smoke test.

 

[lestro]

I've got the voltage regulator, instrument panel, and ecu unplugged, the wiring behind the windscreen looks to be in good shape and yet the fuse blows as soon as you turn on the key. anything else electronic on this?

 

[lestro]

Ok got it, inside the relays are small diodes, the one inside the key switch relay shorted out, I just replaced the diode because I had one, and didn't have another relay. Thanks to all for the help.