1998 Nissan Sentra Electrical

[54Scorpio]

Hello, I just got home form a trip out West and during my absence I allowed a good friend to use my car occasionally. Last night I go out to use my car and none of the interior lights work, nor the tail lights. I call my friend who tells me that he needed to give someone a jump and rather just doing it the normal way of hooking up the cables to the battery he connects the positive cable to the alternator and the ground to the car frame and gets his friends car started. But when he went to use my car one night afterwards he notices the lights that I just said wouldn't work and he chose to let me fix the problem when I got home. My first question is why would anyone jump a car using the alternator rather than the battery? The other question I have is, after I've checked all the fuses located under the steering wheel and found them to be okay, I checked the fuse boxes under the hood and they were all okay. Where do I go next? Any help anyone can give m,e will be greatly appreciated. Thanks

[Crvett69]

there should be a main 60-120 amp main fuse in the fuse box under the hood or a fusible link where battery cable connects to battery, if one of the links is burned out it might cause this issue. you have to test them with a test light or voltmeter, they can look good but be burned out. sometimes they are in a smaller black covered box. should also be able to see if the headlight and tail light fuses get power when you turn lights on

[54Scorpio]

First I'd like to thank you for replying to my question. I might have mislead you in my question. The head lights do come on, but just about everything else is out. I had put a volt meter on the battery while the car was running and it only registered 12.5 volts. I thought that it would have registered closer to, if not over 13 volts. I'm worried that the idiot might have fried my alternator. I didn't see your reply until after I came back inside so I will check those fusible links when I go back outside. While I was outside I did pop the top off of that covered box that is next to the battery that appeared to have three fusible links that had a clear top on them and they looked to be okay, but there were two other wires that seemed to be plugged in to that box also, that might have been fusible links, but I wasn't sure because I've never worked on or checked fusible links before. What are your thoughts about the 12.5 volts on the battery? Would having a fried diode inside the alternator cause the symptoms I've described with just about everything else out besides the headlights(which might just be running off the battery)? Thanks again for your help.

[Crvett69]

chances are he blew the large fuse or fusible link that on the main wire going to the alternator. you have to take the links out to test them, they can look fine but still be melted inside the cover. if you have a voltmeter you can check the resistance with at least one side unplugged, should show 0 ohms. can also see if the largest wire to the alternator has 12v with car off, it should if the fuses and links are good

[54Scorpio]

Thanks once again for your help and expertise! I'll check the things you had suggested tomorrow morning and I'll let you know how I make out.

[54Scorpio]

You were absolutely right! there is a 75 amp fuse marked "Battery Fuse" in the fuse block next to the battery