weird electrical problem - Tilted Forum Project Discussion Community

cj2112 · 01-16-2004, 07:45 PM

I have a '93 Nissan Sentra w/ the 1.6 liter engine. I'm drivin home from work the other night and both my brake light and my battery light come on at the same time (I friggin hate idiot lights, but that's a rant for another thread). I stop by the local Auto Zone to have my battery tested and it tests fine, I leave there and I now have no dash lights, tail lights, gages, wipers, turn signals, brake lights, cigarette lighter, emergency flashers, speedometer, or rear window defroster but my headlights work. So to make a long story short, I check the fuses, they're good check the fusible links, they're good, check the fuses they're good. I let the car sit for a couple of days and I start it up to pull it into the garage and everything magically works again, but the battery and brake light are on again. I had the alternator bench tested and it tests good (14 volts and good amperage). The car runs fine. I am stumped, I have checked everything I can imagine and everything looks good. Help?

Sion · 01-17-2004, 01:24 PM

initial symptoms point to an alternator failure. you should have had that tested when you tested the battery (am I correct in assuming the problem was still occuring when you pulled into autozone to have the battery checked? if so, then that would have been the best time to check the alternator.) however, since the alternator has been bench tested and shows ok, that suggests either an intermittent problem with the alternator (which is rare - once they go, they usually stay bad) or perhaps a loose connection somewhere, if its a loose connection, it may have been remedied when the alternator was reinstalled after the bench test.

if the vehicle has an external voltage regulator (ie one thats NOT in the alternator, have that tested and replaced if necessary.)

Id be willing to bet that whatever the problem is, it is somewhere between the battery, the alternator, the voltage regulator (if external) and the fusebox. it could even be in the computer (depending on whether the comp gets direct current from the charging system or if it runs through the fusebox, and also depending on how much (if any) control the computer has on the electrical system. (for example, on my 92 NY, the voltage is regulated by the computer, as opposed to using a voltage regulator.)

if the problem recurs, check for loosed/frayed/damaged wiring all throughout the charging system (ie start at the battery and trace to the alternator and from the battery to ground (which is usually grounded to the engine block. check also the ground strap from the engine to the frame. this is one of the most overlooked parts of the electrical system, and because it is usually on the lower portion of the engine, is often subject to environmental damage like rust/corrosion or damage from rocks, etc). if all those are good, check the wiring from the alternator to the distributor/ignition coil and to the fuse box. essentially, you are going to have to go trace down every wire in the entire charging system while looking for not only noticable physical damage, but also while moving/shaking each wire every few inches to find a possible internal break/short that is not visible from looking at the insulation, all the while monitoring the continuity of each wire with a multimeter. this can and will be a long, slow and very tedious process, but is the ONLY way you can trace down and eliminate the problem. another way to do it would be to entirely replace all the wiring in the entire charging system with new, known good wiring. this might actually be the quicker way of doing the job, but will be more costly. just be sure to use the correct guage replacement wire. you dont want to use wiring that is too small to carry the load required in any given curcuit, however you dont want to use wire that is too big, as the excess resistance in heavy guage wire can screw things up just as bad.

good luck.

cj2112 · 01-17-2004, 04:02 PM

Thanks Sion, I put the alternator back on the car today, fired it up, and the problem dissapeared, I'm guessing that it was bad groung on the alternator itself. Your post confirmed what I was thinking about having to trace this down one wire at a time...lol. I'm gonna keep an eye on it for a few days and see what happens.

01-16-2004, 07:45 PM	#1 (permalink)
cj2112 Unbelievable Location: Grants Pass OR	weird electrical problem I have a '93 Nissan Sentra w/ the 1.6 liter engine. I'm drivin home from work the other night and both my brake light and my battery light come on at the same time (I friggin hate idiot lights, but that's a rant for another thread). I stop by the local Auto Zone to have my battery tested and it tests fine, I leave there and I now have no dash lights, tail lights, gages, wipers, turn signals, brake lights, cigarette lighter, emergency flashers, speedometer, or rear window defroster but my headlights work. So to make a long story short, I check the fuses, they're good check the fusible links, they're good, check the fuses they're good. I let the car sit for a couple of days and I start it up to pull it into the garage and everything magically works again, but the battery and brake light are on again. I had the alternator bench tested and it tests good (14 volts and good amperage). The car runs fine. I am stumped, I have checked everything I can imagine and everything looks good. Help?

01-17-2004, 01:24 PM	#2 (permalink)
Sion Dumb all over...a little ugly on the side Location: In the room where the giant fire puffer works, and the torture never stops.	initial symptoms point to an alternator failure. you should have had that tested when you tested the battery (am I correct in assuming the problem was still occuring when you pulled into autozone to have the battery checked? if so, then that would have been the best time to check the alternator.) however, since the alternator has been bench tested and shows ok, that suggests either an intermittent problem with the alternator (which is rare - once they go, they usually stay bad) or perhaps a loose connection somewhere, if its a loose connection, it may have been remedied when the alternator was reinstalled after the bench test. if the vehicle has an external voltage regulator (ie one thats NOT in the alternator, have that tested and replaced if necessary.) Id be willing to bet that whatever the problem is, it is somewhere between the battery, the alternator, the voltage regulator (if external) and the fusebox. it could even be in the computer (depending on whether the comp gets direct current from the charging system or if it runs through the fusebox, and also depending on how much (if any) control the computer has on the electrical system. (for example, on my 92 NY, the voltage is regulated by the computer, as opposed to using a voltage regulator.) if the problem recurs, check for loosed/frayed/damaged wiring all throughout the charging system (ie start at the battery and trace to the alternator and from the battery to ground (which is usually grounded to the engine block. check also the ground strap from the engine to the frame. this is one of the most overlooked parts of the electrical system, and because it is usually on the lower portion of the engine, is often subject to environmental damage like rust/corrosion or damage from rocks, etc). if all those are good, check the wiring from the alternator to the distributor/ignition coil and to the fuse box. essentially, you are going to have to go trace down every wire in the entire charging system while looking for not only noticable physical damage, but also while moving/shaking each wire every few inches to find a possible internal break/short that is not visible from looking at the insulation, all the while monitoring the continuity of each wire with a multimeter. this can and will be a long, slow and very tedious process, but is the ONLY way you can trace down and eliminate the problem. another way to do it would be to entirely replace all the wiring in the entire charging system with new, known good wiring. this might actually be the quicker way of doing the job, but will be more costly. just be sure to use the correct guage replacement wire. you dont want to use wiring that is too small to carry the load required in any given curcuit, however you dont want to use wire that is too big, as the excess resistance in heavy guage wire can screw things up just as bad. good luck. __________________ He's the best, of course, of all the worst. Some wrong been done, he done it first. -fz I jus' want ta thank you...falettinme...be mice elf...agin... Last edited by Sion; 01-17-2004 at 01:26 PM..

01-17-2004, 04:02 PM	#3 (permalink)
cj2112 Unbelievable Location: Grants Pass OR	Thanks Sion, I put the alternator back on the car today, fired it up, and the problem dissapeared, I'm guessing that it was bad groung on the alternator itself. Your post confirmed what I was thinking about having to trace this down one wire at a time...lol. I'm gonna keep an eye on it for a few days and see what happens.