[grand94jeep]

Why do I keep blowing a 60a Max fuse under my hood? I have blown the alt pwr 2 fuse in the distribution block under the hood twice in the past 2 months since I replaced my factory alternator with a 136amp off of a 98 ZJ. I carry spares so I don't get stranded, but why would it keep blowing? Any help is appreciated. I've checked the battery wiring and the wiring to the alternator. The only thing I can see that may be wrong is that little black inline connection on the ground wire that connects to the back on the alternator is a little mis-shapened. It looks like it got hot.

I blew the battery and the same fuse about a month and a half ago, about a week after I put in the new alternator. I took the alternator back and got a warrenty replacement and I hadn't had any problems till tonight. I haven't been 'wheeling lately and I have actually been driving sane (i.e. no full throttle take offs). I just got in the Jeep and started to work tonight and noticed the lights were dim. I pulled the fuse and replaced it but now I'm a little gun shy with the Jeep.

Any Ideas?

 

[xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxblackjak71]

sounds like youve just got a short somewhere, trace all the wires that you think may be leading to the problem or ones that youve messed with to doublecheck, thats all i can think of right now

 

[GoingOffRoading]

you may have gotten a bad alternator. Its quiet possable that the brushes or eletronics are bad. Also did you hook up the field negative and positive cables correctly? As long as you installed the cables correctly then I doubt that they are shorting. If there was a bad short (one strong enough that it blew the fuse) in one of the cables then chances are it would blow the second your car started up. Maybe the PCM doesn't recognize the higher amperage of the alternator so when the engine revs the field goes to hell and blows the fuse. Also are you using the fuse that is meant for the new alternator?

 

[TiggersBounce]

am I seeing something too obvious? or am I just blind.

You have a 136A alternator.
Alt pwr 1 = 60A fuse
Alt pwr 2 = 60A fuse
These fuses are in parallel on the same circuit.
That is a total of 120A fuse capacity between the alternator and the battery. And the alternator can produce as much as 136A and try and transmit it to the battery ... and when you get to 121A what might happen?

I wonder though why alt pwr 1 hasn't blown. Now THAT would concern me if it were me ..

:crazy

 

[grand94jeep]

fuse

I had thought about replacing the fuses with a higher rated unit. But if you've ever seen the damage one of these does when it blows you'll understand why I haven't yet. The factory spec 60a fuse almost melted the distribution block when it blew the first time. Last night it only melted the fuse. I don't want to see what would happen if I put in, say, an 80a fuse. The distribution block is a complete (expensive) piece and I don't want to risk damaging it any further. What I don't understand is why it is blowing alt pwr 2 and not alt pwr 1 or both of them? Also, no one else on here recommended having to change to higher fuses with this up grade to a bigger alternator.

If I indeed have a bad alternator, again, then I'll take it back and raise hell with Advance.

This is just what I need right before I'm about to install a winch on my ZJ.

Any more ideas?

 

[mmyers]

what kind of electronics are you running?? Stereo junk? lights?

 

[grand94jeep]

fuse

I have some off road lights and Pioneer stereo with 2 small amps. I didn't have these problems untill I changed the Alternator. I search all over NAGCA and JU about doing this alternator upgrade and saw no warnings about doing this upgrade. At the time all I had on was my head lights and foglights.

 

[dracer69]

i would have the alternator tested at the store. if there is an internal short, then they could tell on the machine. it is very possilbe they got a bad batch of alternators. mass production, it happens, especially w/ auto parts. if it tests bad, i would ask them to special order you one and test it before leaving the store. either way, it isn't the store's fault b/c i've ran into that at all of them.

i would say there might be a short some where though. i would disconnect the lights and stereo for starters and go from there. also check all the wires to see if you can find anything that might have gotten hot and melted some insulation. also replace the plug you mentioned got hot. you might consider a new power wire from the alternator to the battery/starter ( i cannot remember right now where it is routed ).

robert

 

[HUFDADY]

Check the O2 sensor wires, make sure they are not kinked or burned anywhere.

Patrick

 

[grand94jeep]

fuse

Here's a thought. Here at work we have new A/C units that will blow breakers if they're cycled on and off too fast. That night in particular I had the A/C on and forgot something in the house. I shut the Jeep off ran in and right back out, (30 sec.) and started up and headed into work. Could this be a culprit, when the A/C surged back on while the pressure was still high. I've never heard of this before but due to the higher output of the new alternator could it have surged more to kick the A/C back on and blown the 60a fuse?

I might be totally off the wall, or I may be onto something. Just an incident at work tonight got me thinking. :?

 

[Jeep2Relax]

the electricity required to kick on the ac in your jeep is the charge to engage the clutch. the compressor is turned by the drive belt an that big gas consuming engine under the hood. unlike the electric motors that run the ac in a building that V8 under your hood doesn't really care if you cycle the ac to fast.

 

[nate379]

Check the O2 sensor wires, make sure they are not kinked or burned anywhere.

Patrick

Want to explain to us how that could blow a 60 amp MAIN fuse??

 

[blisters]

Do yourself a favor and buy a cheap (12$ to $20) digital voltmeter and check the voltage of the battery after an overnight rest and then after driving for at least an hour. The overnight voltage should be higher than about 11.5 volts DC, and the after-hour voltage (with engine idling) should be over 13 volts DC (and less than 14.5 - 14.8). Low voltage overnight means a weak battery or constant electrical load dischraging your battery, high voltage after hour drive means bad alternator voltage regulator. Either one means high current from alternator adding to the regular electrical loads.

You could also try driving around close to home starting with a charged battery but with all the alternator wires disconnected. If you burn another fuse, that will definitely eliminate the alternator as being defective.

Good luck!

 

[dracer69]

why not just let autozone test the battery and alternator?

they have a nice testing setup that rolls out to the car. it load tests the battery w/ the engine off and the alternator w/ the engine running. it is actually better than removing the alternator and having it bench tested.

i once had a alternator that bench tested fine but under load due to a bad diode trio, it would not put out enough amps and drained the battery.

 

[grand94jeep]

Fuse

I'll go have it tested at Autozone this week.

Jeep2relax-- I get what you're saying about the A/C but why does my voltage drop when the A/C cycles. Just trying to rule out if this was my own fault.

As for the battery, its brand new. Its an Exide Orbital (same as an Optima)

 

[HUFDADY]

Check the O2 sensor wires, make sure they are not kinked or burned anywhere.

Patrick

Want to explain to us how that could blow a 60 amp MAIN fuse??

Well I guess I could...but it doesn't seem as though that's going to get checked anyway.
But just for shits and "us", I'll elaborate...I replaced my water pump once and upon reassembly, I managed to get the O2 sensor wire pinched in the mount for the water pump. Once it grounded it blew the MAIN fuse...repeatedly. So I suggested checking it rather than speculating on and on.

 

[Jeep2Relax]

voltage may drop when the fan turns on and the electric charge goes to the compressor clutch but the draw is supposed to be relatively small. If your ac is burning a 60 amp fuse then your short could very well be in the ac system somewhere. however there should be fuses protecting those circuts that should burn first.
My voltage gauge on the dash always reads lower when the ac is on during hot weather. But the voltage at the battery is fine.
You really need to have the charging system checked (as you plan on doing) to eliminate some variables, since this started happening after the alternator change it is probably related somehow.

 

[grand94jeep]

huff

Sorry Huffdady...I forgot to include that I would try your suggestion too. :cuddle:
I'm off tomorrow so I'll check it all and see. :thumbsup:

Thanks guys, for putting up with a :newbie:

 

[Jeep2Relax]

Hufdady is probably on to something as it is probably something that is not protected by a smaller fuse.

 

[HUFDADY]

Just passing on my .02, hope it helps.

Patrick