HELP !!! - Major Electrical Problem

Heres the short story. I went to go somewhere today, after dark. Keywords, AFTER DARK. Went 2 miles down the road and noticed everything started to get dim and start to die, dim dashlights, radio turning on and off. Turn the headlights off and the voltage guage went back up to 13 volts. I then turned them back on after stopping at a light and got a repeat. I pulled into a lot and got out to look under the hood and at the headlights. My XJ died in the time that it took to open the hood. Wouldn't start and needed a jump. I came to the assumption that with the parking lights on I'm drawing too much power for the XJ to charge the battery up at idle. Cruising on the highway at 3000 RPM's I'm ok with just the parking lights on but no head lights. If I stop at a light the voltage dips if I don't rev it. I'm thinking I either have a short or a major draw somewhere. Looking for ideas on where to start looking and what for or if anyone else has experienced something along theses lines.

90 XJ

Thanks in advance,
Doug

I's suspect that your alternator is going bad, or the battery has a dead cell in it before I suspected a short. A short would cause a fuse to blow, or cause problems at all engine speeds. A dying alternator or battery would make itself most apparent at idel speeds. Make sure that your serp. belt is properly tightened also, could be slipping and not driving the alt at the proper speed.

from what your saying, I would bet when you go out tomorrow you heep won't start.

how old is the alternater? old enough to stop working or maybe just put out a little power, enough to power the ignition but not much else. it sounds like it works fine at 3000 rpm, alt's put out a lot more amps at higher rpms.

just a thought, good luck. I hope it's as simple as the alt.

jinx, you owe me a coke

Thanks, I'll check that in the am... I thought the same about the fuses too. The thing is with the lights off, the alt seems to be charging fine. I haven't driven at night that often lately with this vechicle but during the day it seems fine. I actually drove it a good majority of my day today. Stop and go. Errands and what not. It started right up everytime. If it was the alt I would suspect that just daily driving with the radio on and heat and everything would cause the same thing but it hasn't. It just seems like the parking lights are drawing alot of power all of a sudden.

Nahh its not gonna start because I drove it all the way home tonight about 12 miles with the parking lights on. I got pulled over by a cop and had to shut them off cause the voltage dropped to 8 volts, and then explain the how thing to him. Luckily I was 3 blocks away from my house and he was like just go !. But idling at low RPM's and the lights off the voltage leveled off at 13 volts. It keep the truck running. I pulled in my drive and let it idle with the parking lights on and it crapped out. Yea, its definately not gonna start in the morning. By the way I drove with absolutely nothing on but the parking lights tonight. Pulled out the fuses for the radio and as much as I could. Like I said before I had to have been drawing more with the heat, radio, xm radio, and what not this afternoon. I would think all that would draw more then just the parking lights right ? Unless the alt crapped out after I did all my running around in the afternoon.

Voltage regulator, perhaps? Had the same exact problem in a '76 Volare Roadrunner that my brother had. Real pain in the ass at 3:30 in the morning in the middle of nowhere.....

I was thinking that too... I actually just charged it and ran it with no lights with the radio and heat and it seemed to stay steady at 13 14 volts... When it gets light out I'm gonna pull all the parking lights and headlight bulbs out...

I'm 99.9 percent sure I found the problem... Posting this so if someone else has or will have problem, this might help them. So I put the charger on the battery for a 90 minute charge. Went to start it about 2 hours later and it still wouldn't start. Turns out that it really didn't charge. After analyizing everything I found that there was a bad connection in the battery cable end. Once that was solved the battery started to charge, the guage also on the charger read a 20 amp charge. Once the battery charged up the XJ started up fine but I started to have the same symptoms. I got my dads load tester and tested the charging system which read 13 volts. He said its alright but should be better. So I guess that bad connection killed the battery cause it wasn't getting a charge and might have fried the alternator. Gonna replace the cables cause they're kinda crap, and alternator and possibily the battery. Thanks for the help guys.