Nissan Repair: Charge problems 92 Pathfinder, amp light, high beams

Question
QUESTION: My sister has a 92 Pathfinder. In august we had to replace the alternator. She was driving home a few days ago and the wipers slowed down and the headlights dimmed. She barely got it parked before the truck died. I had the battery charged and checked. Come to find out the alternator was bad so i exchanged it. Still the same problem. Tried 3 different batteries total all after charging to 100%. Still not good. Tested with a voltmeter under load and without and it says the alternator isn't good. So i pulled it out and head back to the parts store and they tested it and swear it's good. The amp light was burned out in the beginning so i replaced it. It lights when the key is on with all the others. When i start the truck it flickers dim most times without change after giving it gas. Also no change if the headlights or other acc. are on. I also checked the fusible links around the battery. Could the parts store be right and I'm not testing something?? I've spent 3 days looking and checking fuses, wires, connectors....I made sure the belt is good and the tension is right. Please tell me I'm missing something easy. Thanks in advance.

ANSWER: Hi Curtis -

Seems to me the alternator is not good.

What was the voltage of the battery when the car is running? How about when it isn't? With high beams on?

How is the parts store checking the alternator, I assume they are load testing it?

Please get back to me -
thanks and aloha
calvin

---------- FOLLOW-UP ----------

QUESTION: Thanks for getting back to me so fast. Ok i took a fresh charged battery. Before starting it the voltage was 12.94. Then started the truck and it was 12.46 at idle with no load. Turned on the lights and it dropped to 12.19. Raised the rpm to about 2000 and no difference. Turned on hi beams and it dropped to 11.94. Again no difference with higher rpm. The whole time the amp light was flickering. So im about to pull out the alternater AGAIN to go have it re-tested. And the parts store uses it's bench tester. I'm assuming it does a load test along with checking the regulator, diodes, etc. in the alternater. Any other ideas incase it says good?? Thanks again..

ANSWER: Hi Curtis -

OK thanks for the info. The battery is definitely not charging. Before you take the alternator out again, make a final check on all connections to and from the battery, with respect to the alternator circuit. This includes cleaning the battery terminals and insuring tightness. The alternator circuit also has a fuse which you can check, it is usually in the engine on the fender well, in a plastic box with other large circuit controls.

Another on car test you can do is to use the voltmeter and check voltage at the field terminal of the alternator (usually labeled "F"), and is the red wire. While the engine is running, it should read about 14 volts. If it is, then leave the alternator in and look for a disconnected or loose wire somewhere.

If all checks out, then I guess it is time to remove and retest.

Please keep me posted -
aloha
calvin

---------- FOLLOW-UP ----------

QUESTION: Well it was too late about removin the alternater. I had it retested and it was good. But i already did teh test on the alternater post. (Just fyi the wire is white ;). It read the same voltage as the battery. Even with the car running and lights on. But the parts store again swears it's good. They even tested it twice.
 But this time i got lucky and the guy that works there just quit working at Nissan as a service tech. (supposedly). He says that i should start checking the starter and wires for the starter. (I'm not looking forward to. Alot more to check than the chargeing system). So i started looking at the schematic again and came across the A/T oil level sending unit on the tranny. It shares the wire that goes to the amp light. I climbed under the truck and the wire had been *repaired* before (for lack of a nicer definition) Not very well!! The wires were really stiff and the housing was cracked in several places. Not to mention melted from sitting on the exhaust manifold. My question is i know it fried something that i haven't found yet. Any suggestions what or where to test? I would rather not spend another 3 days hunting. I would even more rather not have to pull the starter. Been there done that a couple times in the past. Me and my sister thank you for keepin patient. I just found out she even tried to pay some site to help her and they wouldn't or couldn't. THANK YOU!!!

Answer
Hi Curtis -

Thank you for the information.
Well, I would say you will have to get into "diagnostic mode" and check circuits and wires, predominantly the ones that have touched the exhaust. Funny, but if that wire did touch the exhaust, it would have blown the fuse, and you would be able to find the issue. Sometimes these circuits are protected by a fusible link, looks like a wire, but if there is a short, it breaks inside the insulation, so it is hard to find without a circuit tester.

I wish I was there to assist, but if the alternator is OK, the answer is to trace wires.

Let me know how it goes -

aloha
calvin