Battery ... Jeep cranks but won't turn-over

Ok. So I went out to the Jeep to test the battery because I suspected a drain on the system. As I was testing it something else came up and I had to leave the Jeep rather quickly. When I came back I reconnected the cables backwards (forgot I had spun the battery around before I had to leave the Jeep). So there was a big spark, lots of sparks and I left the cables hooked up for a good 20-30 seconds before I realized what was happening.

Now the Jeep won't start. There was an electrical burn smell coming from the vicinity of the fuse box / right side of the engine bay. I checked the fuses and they seem good. I opened the box with power applied (key to on) and one of the relay boxes is making a buzzing noise. Also my radiator fan is coming on, but the engine won't turn over.

Edit: The radio works, headlights work, blinkers work. All electrical items seem to work fine.

Is it the starter? Fuses? Regulator? Alternator? Please help. Thanks.

There was a 15amp fuse blown. It's running now. But the alternator might need replacing.

What were you using to test the battery?

multimeter. I checked the batter at about 12.5V before starting (after the episode), with the vehicle running it was max 13.2. Constant at 13.1

I should have added to my post that I don't see how a multimeter connected backwards would cause all that sparking etc. As far as I know, most modern meters don't care -- they just show a (-) voltage if the probes are reversed.

In any event the good news is that everything appears to be in order.

Pelican said:

I should have added to my post that I don't see how a multimeter connected backwards would cause all that sparking etc. As far as I know, most modern meters don't care -- they just show a (-) voltage if the probes are reversed.

In any event the good news is that everything appears to be in order.

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I think he means he connected the battery terminals backwards.

^^ yes.

Is 13.1V at the battery with the vehicle running enough to "get by" until I pick up a new alternator?

OnorOffroad said:

^^ yes.

Is 13.1V at the battery with the vehicle running enough to "get by" until I pick up a new alternator?

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My old alternator maxed at 13.1 and could only push a constant 12.8, this caused tons of problems; my Jeep would run funny, misfire when I started it all the time, the A/C didn't work, and some more stuff I'm not remembering.. It was a mess.. I swapped in a GC 135A alt from the junkyard and this fixed all of my electrical problems and some other things I didn't think an alternator could affect.

My XJ is a 2000, so it might not be as bad on an older one, but a crappy alternator caused butt-loads of problems for me.

I replaced the alternator with a durango 136amp alternator. Now at idle the battery is showing 13.7-13.8 and the voltage gauge is showing just about dead center at 14V. All is well with the charging system for now.

I discovered that the blower motor isn't working. I haven't found any more blown fuses. Can the blower motor be fried? Or could it be something else?

OnorOffroad said:

I

I discovered that the blower motor isn't working. I haven't found any more blown fuses. Can the blower motor be fried? Or could it be something else?

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The blower motor should not have been damaged by the reversal. Try the blower again with the blower speed set to maximum. It will most likely work there. If it does, the series resistor is burned out.

IT didn't work at max. I can hear the slight hissing sound that usually comes out of the hvac controls when switching from/to AC/air. But the blower never comes on. I'll check the fuses again, check the resistor, and then check the blower motor. I am hoping it's one of these three and not something in-between.