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Truck is a 2003 f-350xl z-f6 dually extended cab with about 255k on the clock. I got this truck for free about 6 months ago and don't know much of the history, it is in overall great condition. for the last six months once in a while the battery light would come very dim at low rpm and then increase in brightness as rpm went up. If i would get it on it pretty good, about 3200 rpm the light would go out and not come back. earlier this week we got pretty cold in Montana. about -10 wind chill and 5 above actual temp Tuesday morning. Being in construction we decided to do a late start and start at 10 to let it warm up a bit. I was excited because i actually got a chance to take my kiddos to school and let my wife stay home. Anyway, on the drive to school, about 15 drive down back roads, i first noticed the radio went black, looked down and had no gauges, this time the battery light never came on. Drove to school, left the truck running, took the kids inside said goodbye and drove straight to napa, about 5 minutes away. They said the could test the alternator in the truck if it would start under its own power. shut it off, tried to start again, nothing, completely dead. I had a fairly bad positive battery connection so i fixed that at the store. Finally got the truck jumped off another powerstroke, it took about 30 minutes of charging before it would start. All gauges and radio came right back to life, let it run for about 15 minutes and hit the highway, made it about 1 mile, lost the all gauges again, truck started to shutter, lost power and i coasted to the side. Took the batteries home, Charged to them to full, replaced the alternator, Started truck, everything good for about 5 minutes Battery light back on except this time extremely bright at idle where before it was very dim if it came on at all. Truck seems to run perfectly. I had both batteries tested and both test good 890 cca. All battery connections are cleaned and tight. Any ideas. thank you
Some have experienced issues with the alternator plug connector and loose wires - worth a shot to wiggle that connector/wires to see if the light goes out. Pretty sure I know the answer, but do you monitor your battery voltage at all? If so, what is it? You can also put a meter on the alternator itself to test voltage.
The battery light turns on because the voltage is lower at the alternator then it is at the batteries - the truck is running off the batteries.
A NAPA alternator was the last aftermarket rebuilt alternator I ever bought, it was bad out of the box.
You need a meter to test voltage and continuity. As jokester said, with a good alternator you can still have issues if the wire connections are bad. That can be the two-wire connector at the alternator, the power lug eyelet at the alternator, the fusible links in the cable from the alternator to the battery, or the eyelet at the battery connection.
First, take some pictures of the top of your batteries and the alternator connection so we can look at them. Sometimes we find goofy things, like the power cable between the two batteries being bad, so the alternator charges the passenger battery while the drivers side battery depletes.
I just watched a video on how to test to the voltage at the alternator, I will do that tomorrow, I do not have a way to
monitor battery voltage, what do you think the answer is?
That's crazy that is the video i watched before the last comment. that is the best and most informative video I have ever watched. Thank you for your help.
We've had some unusual things that have caused situations such as yours. With a 6.0L, it's highly recommended you get a method to monitor all the sensors and aspects of the PCM diagnostic capability, that includes voltage. The best to get is the Forscan app and a plug-in OBD2 port reader. That will get you almost to dealer-level data, and it is the very best at reading codes. It won't diagnose charging issues, but it gets you the voltage readings.
Either of the two that I have work, but most people like the more expensive version.
Realtime monitors like Scangage II are available, but not as good at reading codes, or something like this can be used and easily switched between vehicles. But pwerports can read from 0.5 to 1.0 lower voltage than what is occurring at the battery due to wire and contact loss.
But do get pictures of your battery terminals so we can see what is going on.
Here are the pics of batteries, Last night when i put the new alternator in and then pulled the truck out of shop is when the battery light came on, and it came on brighter than i have ever seen. I just got home and started the truck, I let it warm up for a 30 minutes and pulled it back into shop (literally 50ft) The damn battery light never came on this time, It must be a loose wire. I am going through everything in the video Tomanytoys posted tomorrow step by step, Just wanted to get the pics uploaded
This is your cable from the alternator to the battery. I had just gone though a battery issue with a guy on YT and had private conversations on PD.org. He had something similar, and while he initially tested the wire and it seems fine, the wire had an issue by the eyelet and would have an intermittent connection.
After fallowing "Toomanytoys" video here are my findings. Tested both batteries and both tested 12.6, I had to move the truck twice so they were used a little. Tested the big red wire at the alternator it also tested 12.6.
tested the jumper wire to the starter and everything sounded perfect. Tested the two wire connector at the back of the alternator. First wire tested 12.6 with key off, second wire tested 0 with key off. with key on the second wire tested 12.6.
reconnected plug and started truck, tested alternator and watched the volts climb for the 90 second glow plug cycle and then had a steady 14.38 volts coming from alternator. and the battery light still on. If i unplug the two wire harness while truck running the battery light goes off, Should it do that? The two wire harness at the alternator was not clipping into place so i replaced that tonight. in the process of stripping the wire i accidently arced my strippers to the bolt on the alternator( is there a fuse i could have blown?) After hooking up new pigtail i re tested everything and it all tested the same. Started the truck and no light, let it run for a few minutes backed out of the shop and went inside to have a victory beer, I left it running to recharged the partially drawn down batteries Came back out 10 minutes later and the damn light was back on, With the truck still running I tested the alternator again and was still getting 14.38 volts.
Do you think it is safe to drive the truck? is it possible to have a short that is causing the light to come on when it is not supposed to?
Here a couple things i thought are weird about this truck and charging issue.
When the gauges first went down and truck was not charging the battery light never came on
I figured it was the alternator because when the battery light would come on it would get brighter as the rpms climbed and usually go off if you went past 3200rpm. My guessing was that it had to do with how fast the alternator was spinning.
The light only came on fully after installing new alternator. I have not driven the truck since new alternator just pulled it in and out of shop.
Any other comments or ideas are greatly appreciated, electrical is my enemy
I going to post to your the area in the service manual for diagnosing this. At first glance, I'm still seeing an alternator issue. BUt I've dead tired and a hour past when I thought I was heading to bed.
Going through the steps troubleshoots the issues. It's not perfect.
Shorting the power terminal has the potential for burning the fusible links. The best way to have avoided that would have been to disconnect the red 4ga wire that I pointed to in the early picture. 8mm nut and power is not going to the alternator. At this point, you want to retest to see if the links are blown or not. So without the engine running, test to see if you have voltage at the shorted post, and move the wires around down by the battery at the same time. If the links are blown, the alternator is no longer connected to the battery and the 'battery' light will be on.
If the links are blown, the easiest thing to do is install a 4ga wire in place of the factory one, alternator to battery. Later we can discuss how to fuse that. But leave the existing cable connected at the battery. Tape up the original eyelet at the alternator to prevent shorting, just because.
Tomorrow I'll get back to here.
Edit - Got out of bed to correct this. Your original light may have been poor contact from the plug not locking in place. The light on now may be the fusible links blown.
Question, If the fusible link is blown, Would my batteries still be showing 14.38 volts while the truck is running
Couple things i thought of in the middle on night, not sure if they are connected, The dome light works only sometimes and sometimes does not turn on at all, also the radio sometimes doesn't turn off and i have to manually do it by holding the power button.
Also when i grounded out on the alternator bolt if was not the 4ga big red wire, it was the small orange wire going to the connector on back.
I am going to grab a 4 gauge wire at lunch and see if that helps,
there is also a grounding wire from the passanger battery to the fender, looks like about a 4ga also, I noticed last night it seemed a little loose in the factory connector at the terminal so i am going to grab some stuff to fix that also
If you are getting the 14.38v, then the fusible links are fine, don't bother with a layover cable to he alternator. The ground wire is an 8ga. Replace it with the like, but I would also do a similar wire from the drivers battery to the inner fender.
With the dome light and radio issues, that's pointing more to having a gauge cluster issue rather than the alternator/connector issue we're focusing on. While it's infrequent, it has been a documented issue. Clusters can be tested and repaired at CircuitBoardMedics. They have done a fair share.
New findings tonight, I got some new crimpable wire connections and a couple pieces of wire at lunch today, 1 4ga red and 1 8ga black I replaced the wire connections on the wire from the alternator to the battery as it had quite a bit of open wire showing. I thought this wire was supposed to be 4ga. as you can see in the picture a 8ga wire connector fit perfectly, not sure if someone has messed with this in the past and put a smaller gauge wire in place, also the wire sheathing is in terrible shape. None of the wires inside look damaged or exposed but i honestly don't know
I put a new connection here and did not do a layover wire, i also redid the ground wire to fender connection as it was also showing a bunch of bare wire and felt loose to me. I did add the same wire to driver side battery. after reconnecting batteries i did the test with multimeter again. everything tested good except the right side of the plug on the back of the alternator, with key on it only tested 11.56 volts. I did not give time for the glow plugs to cycle, not sure it that effects this. I started truck, it started just as normal and no lights. did all the test again. 14.4 at the the alternator and now 12.38 at the wire on the right side of alternator. Just after 6 minutes of idling the battery light came back on. With the light on i tested the alternator again and this time it was 15.42. Isn't that too high? What would cause this? If the alternator is producing too much would this cause the battery light?
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