Alternator and Fuses

[Extremerc12]

Hello All,

Have a 2003 Explorer EB with the 4.6L. My mom gave me a call today and said the truck battery was dead and the starter relay was clicking. No big deal, she jumped it and was on her merry way. I got home a couple hours later and she had indicated it was dead again and wouldn't start. I went and check it with my Snap on Load/Charging tester. Battery was around 11 volts, but didn't fail the load test. I went ahead and tried to jump it, but at that time it was too dead to start. I let it charge and get it fired up. At this point I hooked back up to the battery with the same Snap On Load/Charge Tester as mentioned above and realized while the truck was idling, it was around 11.7-11.8 volts. When reving it dropped to about 11.5. This is a clear indicator to me that the charging system isn't working. Now my questions are this. Is there a fusible link (mega fuse) or normal fuses in either fuse panel. I looked through the fuse chart, but nothing was jumping out at me. If there is a fusible link (assuming 150-175 amps) where would it be located?

Any other potential thoughts?

Thanks

 

[Avancamp]

Maybe I'm reading it wrong but I doubt it's a fuse. Seems to me the altenator is not charging like it should. To test it jump start it and keep it running and unhook the battery.

 

[imp]

Get it running and while running, check for alternator output voltage at the alternator itself. If you find zero, or near zero volts, the alternator is dead and you can stop looking for a fusible link.

I believe the alternator output to the battery contains NO fusible link, as alternators' voltage regulators protect against overloading, but, could be wrong. imp

 

[Extremerc12]

I'll check it out tomorrow and see what I find.

Thanks

 

[Extremerc12]

Hello All,

First off, Merry Christmas.

Got a chance to check out the truck a bit more today. I charged the battery over night, so all is good there. I got the truck running and completely disconnected the battery and it remained running (12.7-12.8 volts on the battery cables). I connected everything back up to the battery and was reading around 12.7-13 volts while running. I had my load tester/ charging system tester plus my fluke meter on it to test. I guess the alternator is outputting something. With that said, the only other thing I could test and is the voltage at the alternator. The question I have, is what is the best way to do this? There is a two wire molex plug and a straight bolted negative to the alternator.

Thanks

 

[imp]

Hello All,

First off, Merry Christmas.

Got a chance to check out the truck a bit more today. I charged the battery over night, so all is good there. I got the truck running and completely disconnected the battery and it remained running (12.7-12.8 volts on the battery cables). I connected everything back up to the battery and was reading around 12.7-13 volts while running. I had my load tester/ charging system tester plus my fluke meter on it to test. I guess the alternator is outputting something. With that said, the only other thing I could test and is the voltage at the alternator. The question I have, is what is the best way to do this? There is a two wire molex plug and a straight bolted negative to the alternator.

Thanks

The heaviest gauge (thickest) wire feeds current from the alternator to the battery. I would carefully scrape a bit of the insulation off that wire, wherever it is convenient, close to the alternator, don't cut through the conductor, just expose it enough to clip on an alligator clip, then measure voltage between that wire and a good grounded area. Use caution to avoid the exposed wire or clip to contact any part of the vehicle. Carefully tape up the exposed area when finished using black electrical tape. imp

 

[Extremerc12]

Hello Imp,

I removed the engine cover and the boot to the "heaviest cable" and used my All and push up into the crimp. The alternator was between 13.3 and 13.4 volts at this point. Contacts were clean with no corrosion or oxidation.

extreme

 

[Extremerc12]

To add just a little bit, I checked it again this morning. I tested the battery voltage before starting the truck and it was around 12.14 volts. Seems like it has dropped off a bit since charging but is still passing load test as best I can tell. Might need to use a new tool to check this to confirm. With the truck running, I was reading 13.55-13.60 volts at the battery with everything off. When I turned lights, heat and radio on, it dropped to 13.18 volts. When I shut the truck off, it had somewhat of a higher voltage on the battery, starting at 12.7 volts but dropping back to the 12.1-12.2 after a minute or so. I did a couple voltage drop testing and continuity testing between contact points, and everything seemed good. I am beginning to wonder if this battery might just be the issue. The alternator spins without rough spots, isn't loose, belt is tight and it doesn't wine from what I can tell. The power steering does enough of that anyhow.

 

[imp]

If the alternator maintains voltage with many accessories on, as you mentioned, it is not likely to be the culprit. I would agree the battery may be at fault. imp

 

[Extremerc12]

Imp,

Going with the battery theory, I checked and saw the battery was still under warranty. Made a trip over to Advance Auto (Advance Auto Battery) and they claim its good even though my load tester showed them it was right on the line between good and bad. They rapid charged it after the initial load test to see if a cell was dead. With that, I was unable to warranty the battery. So I had them test the alternator in the truck. Their tool indicated the alternator wasn't putting out voltage. Keep in mind my testing in previous posts. I told Advance Auto this and they just stayed on repeat with their statement. The truck indicated the battery level was above half and the charging system was good.

Following this, I went on over to Autozone, they tested the alternator and it reflected a bad voltage regulator. The difference at Autozone was they confirmed my 13.18 volts with the lights, radio and heat on. They also indicated the battery was at 11.8 volts. That could not have been correct based on what the truck was indicating and the fact the starter was spinning quickly without hesitation.

With all this, I am being led to believe there is a alternator problem, but I am not convinced. Thoughts?

 

[05XLimited]

Another way to test a loaded alternator in these is to run the rear defrost with other electrical accessories and test the charging system with the vehicle running. The rear defrost is a greater load on the system and in my experience shows weaknesses in the battery vs. alternator.
Another thing to check is to accelerate quickly, as an issue with the alternator will show up when the engine is under heavy load/at high RPM. If possible, try getting an OBDII reader with logging capabilities. That way you can see what the vehicle does at different engine speeds/loads.