Help Me! Electrical Problems!! FUBAR!!!

Ok today my son was replacing the battery in my jeep and he reversed the polarities on the cables. I thought he could do it on his own so I figured I should trust him. As you all know, this is huge NO-NO!! Not surprisingly he said there was smoke coming from the fuse box and sparks from the battery. Now, my radio and heater/AC fan wont blow any air or just doesn't work at all. I checked the fuses and when I put a new fuse for the heater, it blew as soon as I turned it on. Also, when I start the car, the battery guage is only reading 6-6.5 volts.

Did my son fry my electrical system? Or is it just a fuse (hopefully)?

Please Help ME ASAP!!

2000 XJ.

The radio probably has an in-line fuse in its wiring harness, and you may need to pull it out to find it.

My first guess is that the reversal fried one or more diodes in the alternator, and you should have the alternator tested. You should at least get a voltmeter and test the voltage at the battery terminals when it's running. It should be in the neighborhood of 14 volts.

Matthew Currie said:

My first guess is that the reversal fried one or more diodes in the alternator, and you should have the alternator tested.

Click to expand...

Second that.

yikes man. not to be scary or anything, but a couple of friends of mine were replacing a clutch for some chick and they took out the battery (whoever knows why) and the dumb pot head one put it in backwards and fried the hondas entire electrical system. computers and real expensive stuff. so now its a $14000 japanese paper weight

Oh man.....

Well it starts and runs fine but the heater and radio don't work, so think (hope) its not that bad.

Its almost certain your alternator is history. This has to be checked / replaced before you look any further into the electrical system. The radio may be totally fried also, if so its likely cheaper to replace it than try to have it repaired. The computer / TCU / ABS computers have polarity and overvoltage protection built-in.

If there is still trouble with the heater fan, see if it works only on high speed. There is a little diode in the resistor unit, and if this burned out, it won't work on lower speeds. The motor itself should be immune to reverse voltage.