Last weekend drove from Denver to Western Indiana. Truck sat for a few days and now has an intermittent Service Charging System Now warning on the dash. In trying to replicate the issue, it usually comes on at first start when the truck has been sitting for a while, and then will go off after 10-15 minutes of driving. Truck starts up just fine, no slow crank.
I have dual alternators and have been monitoring with ForScan. From what I can tell the truck is asking for the main alternator to run at 50% capacity (per GENMON reading) but it's not getting the juice. It'll show "Fault" or "Low Fault" on GENMON_LS. So it bumps GENMON2 up to required power (30ish%) and the truck seems to run fine, but the light stays on. After a period of time I'm assuming the primary alternator starts putting out power and it shifts GENMON to 30ish% and only 5ish% out of GENMON2. I haven't figured out how to read alternator/generator output directly, but I figure there's 3 possibilities at this point:
My real immediate question though, if I get zero juice from the main alternator on my 1,150 mile drive home, what are my risks? The 2nd alternator seems to be able to keep up just fine (GENMON2 has only asked for 35-40% power) and is keeping the batteries fully charged. As long as that continues, I really see no issue in getting it home and fixing it there. If I was hearing nasty bearing noises from the main alternator I'd obviously be worried about the pulley grenading and taking out the fan belt, but not hearing any bad noises.
If it was just me I'd run it for the drive home and not even worry about it, but I've got my dogs with me and one of them is older and doesn't handle heat very well. Would rather not be stuck on I-70 in the heat with him right now.
My buddy that I'm staying with has a '19 6.7, he might just catch me outside tonight pulling his alternator out LOL
I have dual alternators and have been monitoring with ForScan. From what I can tell the truck is asking for the main alternator to run at 50% capacity (per GENMON reading) but it's not getting the juice. It'll show "Fault" or "Low Fault" on GENMON_LS. So it bumps GENMON2 up to required power (30ish%) and the truck seems to run fine, but the light stays on. After a period of time I'm assuming the primary alternator starts putting out power and it shifts GENMON to 30ish% and only 5ish% out of GENMON2. I haven't figured out how to read alternator/generator output directly, but I figure there's 3 possibilities at this point:
- Main Alternator not receiving the signal to power up
- Main Alternator is on the fritz
- Main Alternator is receiving the signal, is providing juice, but not reaching its destination
My real immediate question though, if I get zero juice from the main alternator on my 1,150 mile drive home, what are my risks? The 2nd alternator seems to be able to keep up just fine (GENMON2 has only asked for 35-40% power) and is keeping the batteries fully charged. As long as that continues, I really see no issue in getting it home and fixing it there. If I was hearing nasty bearing noises from the main alternator I'd obviously be worried about the pulley grenading and taking out the fan belt, but not hearing any bad noises.
If it was just me I'd run it for the drive home and not even worry about it, but I've got my dogs with me and one of them is older and doesn't handle heat very well. Would rather not be stuck on I-70 in the heat with him right now.
My buddy that I'm staying with has a '19 6.7, he might just catch me outside tonight pulling his alternator out LOL
