CHECK CHARGING SYSTEM while towing
First post. Didn't want it to be in this section. I've had a great time lurking, but I'm stumped with my problem. Here's the timeline:
Background: Bought a 2008 Job 1 F250 4x4, XLT, SRW, CC about 4 months ago. Put a fifth wheel hitch in, bought a fifth wheel and towed the FW about 6 times over hilly terrain to local campgrounds with no problems.
Today: A friend of mine bought a FW but needed me to tow it home for him today. I hooked up as usual. No indication that anything was wrong electrically. Got all normal indications as far as passing the turn signal/brakes/flasher check. Had the trailer brake gain indication as expected as soon as I plugged in the trailer plug.
Took off down the road. While getting on the highway, the battery light illuminated on the dash. I continued to drive the truck to the next exit. While driving, all gauges on the dash and the trailer brake gain indication cutout. Gage needles fell, gain indication went out. Then they came back with the battery light still illuminated. Then they went out and came back. This happened approximately 4 times.
We made it to the next exit, pulled into a parking lot and I unplugged the trailer from the truck, went back to the truck. Battery light remained illuminated. I pushed on the accelerator and the battery light cleared. My friend and I then started to check out the camper. I asked him to check the battery level on his battery indicator inside the camper. Dead. Didn't even light up the "E". Went to the battery compartment and saw that the previous owner still had the battery disconnected and the leads were in contact with the chassis. At this point, I accounted the battery light and loss of gages to the battery leads in contact with the trailer chassis. We taped off the positive lead, plugged the camper back into the truck and continued down the road.
Shortly after getting back on the highway, battery light comes back on. Now I'm concerned that my truck batteries are going to die and I won't have any source of trailer brakes. I pushed the HOLD TO PERFORM SYSTEM CHECK and it comes up with CHECK CHARGING SYSTEM so we pull off again. I start to check fuses in both the passenger compartment and the power distribution block. No smoking guns. I call the nearest Ford Dealership and they agree to squeeze me in. I tell my buddy that I'm concerned about the trailer brakes and that I needed to get the truck checked out before we continued on (still had about 30 miles to home). He agrees and he and his family stay with the camper in a BJ's parking lot while I run 6 miles down the road to the dealership.
After the camper is unhitched, I'm off to the dealership. No battery light though. I push the button, CHARGING SYSTEM OK. Now I'm baffled. I continue to the dealership and explain the situation. They offer to run a Charging Systems Diagnostic. Diagnostic comes back clean. No charge (no pun intended). Thanks Ford. I'm on my way back to the camper. On the way, I ask my buddy to reconnect his battery and see if it is indeed dead. It was. He buys a new battery and installs it in the parking lot before I get back.
Back on the road, battery light comes back on. ARRRRGGGGHH! I decided to continue. This time though, gauges never died, Trailer Brake gain stayed lit. A few more miles down the road, battery light goes out. Now I'm puzzled, but feel pretty confident that we're still safe. Over the next 25 miles, the battery light cycles on and off approx 5 more times. I determine that when the engine is worked hard (i.e. pulling up a steep incline, above 2500rpm), the battery light will come on within a few seconds of going over 2500rpm.
We make it back to my buddy's place safe and sound, unhitch and I'm headed home, obsessing about the battery light. I decided to pull my camper around the block and see if my camper will recreate the problem. Sure enough, pulling up a hill close to my house, the battery light comes on. I've never had this happen prior to today.
1-Only happens when I'm towing the FW.
2-Battery light comes on only when the engine rpm exceeds approx 2500rpm.
3-Fuse 33 TRAILER TOW BRAKE CONTROLLER, TRAILER TOW BATTERY CHARGE RELAY COIL not blown (located in Passenger Compartment)
4-Fuse 44 TRAILER BATTERY CHARGE RELAY not blown (located in Power Distribution Block)
5-Relay 56 TRAILER TOW BATTERY CHARGE operating correctly (checked for continuity with jumpers and a 12V power source).
My theory: The cause of the problem was the loose battery leads coming in contact with the chassis of the camper. My truck was essentially trying to charge the chassis and the campers motion was causing the leads to move and sporadically short, which in turn caused my gauges to die, come back to life, die, etc. This also smoked a component in my trailer charging circuit. The dealerships diagnostic passed because the trailer charging circuit no longer had anything plugged into it, therefore was never truly tested. When the camper was plugged back in, problem returned. That's why I have the problem with both my buddy's FW and my own.
Where to go from here: I've checked the low hanging fruit (fuses, relays). Fuse 33 seems to indicate that there is a charging coil. I don't know where this is or how to test it. My 30-second Google search provided nothing.
I could coordinate with the dealership for a diagnostic with the camper attached but I would have to recreate the problem right before I pulled the truck in. The battery light goes out approx 10-15 minutes once the engine rpms settle out. I'm not sure of the size of the diagnostic machine but I'm assuming that the dealership wouldn't be too keen on me having the camper attached. Additionally, since I have a FW, I had an in-line trailer harness put in the bed of my truck, so there's a chance that a technician would tell me that it's probably the harness and start with that, when in fact, I'm very confident that it isn't.
I'd appreciate any troubleshooting ideas you might have. I've taken the truck with no camper attached on the same roads and worked the engine in the same manner to try and recreate the problem without the camper attached, but it never happens, thankfully. This is why I'm sure that it's limited to the trailer charging ckt in some way.
Again, thanks in advance.