SloneRanger
New Member
Hi all:
New guy here, plus new to the 2nd gen Expedition. Recently bought an 03 XLT 5.4 with 146k as a cheap get-to-work truck. Good condition, no rust, everything works... but the "check charging system" error and battery light are constantly on. I'm relatively mechanically inclined, so I assumed it was a weak alternator or battery... it's proving to be tougher to diagnose. Here's what I know:
- I had the system tested at two parts stores; AutoZone quickly gave me a "you need a new battery" and moved on, even though the battery was sitting at 12.8v with the truck off. He didn't even want to load test it until I pressed him to do so. Got a second opinion at Advance - per their machine, everything passed.
- To diagnose the potential bad battery, I swapped batteries with my wife's 2012 Suburban. Her battery still gave the same errors in mine and my battery charged perfectly in hers. I don't think it's the battery.
- Thinking it's the alternator, I bought an OEM junkyard pull for LKQ from an 03 with 89k miles. When I received it, it looked like UPS had played soccer with it for a couple weeks. That alternator was completely dead and didn't charge at all. LKQ refunded my purchase and let me keep the bad alternator.
- I have tested with my meter (and analog one, unfortunately, so not super specific) and got just shy of 13v while off, 14v while idling, and a tiny touch higher under a 1500rpm-ish load with lights/radio/AC on.
- I tested the alternator cable from the battery for continuity; all good there, too.
Since those testing steps, I have driven the truck quite a bit more; currently I've put about 1000-1200 miles on it since buying it. Driving it to work on dark mornings, I noticed that my lights (interior and headlights) seemed a little dim, so I watched the charge gauge closer. When I start the truck (starts fine every morning), if I turn on the lights, radio, HVAC, etc... I can watch the charge gauge dip. If I leave it idling long enough, I can actually watch it go down. So the alternator is NOT charging right off the line when started. HOWEVER... and here's the weird one to me... once I put some load on the engine, the alternator "wakes up!" The lights get brighter, the gauge goes to it's usual slightly above center location and all is good. This all seems to happen once I hit around 2000rpm the first time. After that, it keeps charging just fine even at idle. I can rev the engine right after starting and it'll kick in just fine, or I can just drive normally and by the time I merge onto a street, it's good.
All this said to get to the point that I think the alternator IS bad. Maybe voltage regulator? What do you guys think? And on top of that, what would you do? I don't want to spend hundreds of dollars on a new OEM alt... do I a) buy another warrantied junkyard pick, b) buy a rebuild kit and rebuild one of them myself (if so, which? The OEM?), or c) just buy a quality aftermarket alternator?
Or am I missing something else altogether? Thanks everyone! I have to get this fixed before winter comes and I need warm the truck up before leaving... and the battery drains before I remember to rev it up ha ha.
New guy here, plus new to the 2nd gen Expedition. Recently bought an 03 XLT 5.4 with 146k as a cheap get-to-work truck. Good condition, no rust, everything works... but the "check charging system" error and battery light are constantly on. I'm relatively mechanically inclined, so I assumed it was a weak alternator or battery... it's proving to be tougher to diagnose. Here's what I know:
- I had the system tested at two parts stores; AutoZone quickly gave me a "you need a new battery" and moved on, even though the battery was sitting at 12.8v with the truck off. He didn't even want to load test it until I pressed him to do so. Got a second opinion at Advance - per their machine, everything passed.
- To diagnose the potential bad battery, I swapped batteries with my wife's 2012 Suburban. Her battery still gave the same errors in mine and my battery charged perfectly in hers. I don't think it's the battery.
- Thinking it's the alternator, I bought an OEM junkyard pull for LKQ from an 03 with 89k miles. When I received it, it looked like UPS had played soccer with it for a couple weeks. That alternator was completely dead and didn't charge at all. LKQ refunded my purchase and let me keep the bad alternator.
- I have tested with my meter (and analog one, unfortunately, so not super specific) and got just shy of 13v while off, 14v while idling, and a tiny touch higher under a 1500rpm-ish load with lights/radio/AC on.
- I tested the alternator cable from the battery for continuity; all good there, too.
Since those testing steps, I have driven the truck quite a bit more; currently I've put about 1000-1200 miles on it since buying it. Driving it to work on dark mornings, I noticed that my lights (interior and headlights) seemed a little dim, so I watched the charge gauge closer. When I start the truck (starts fine every morning), if I turn on the lights, radio, HVAC, etc... I can watch the charge gauge dip. If I leave it idling long enough, I can actually watch it go down. So the alternator is NOT charging right off the line when started. HOWEVER... and here's the weird one to me... once I put some load on the engine, the alternator "wakes up!" The lights get brighter, the gauge goes to it's usual slightly above center location and all is good. This all seems to happen once I hit around 2000rpm the first time. After that, it keeps charging just fine even at idle. I can rev the engine right after starting and it'll kick in just fine, or I can just drive normally and by the time I merge onto a street, it's good.
All this said to get to the point that I think the alternator IS bad. Maybe voltage regulator? What do you guys think? And on top of that, what would you do? I don't want to spend hundreds of dollars on a new OEM alt... do I a) buy another warrantied junkyard pick, b) buy a rebuild kit and rebuild one of them myself (if so, which? The OEM?), or c) just buy a quality aftermarket alternator?
Or am I missing something else altogether? Thanks everyone! I have to get this fixed before winter comes and I need warm the truck up before leaving... and the battery drains before I remember to rev it up ha ha.
