Battery light is on but alternator is charging

vandiesel · 09-06-2020, 09:43 AM

I have a trip coming up next week and of course my battery light just came on. Scanguage shows 14v charging so not sure what is causing it. I have a new 270amp alternator and 2 brand new odyssey batteries. Since I'm heading to lolo pass and magruder corridor I don't want to go off grid knowing I could have a stranding issue. Anyone know what would cause the charging light while voltage looks fine?

carringb · 09-06-2020, 10:18 AM

Bad diode diode in the rectifier. You can swap out only the rectifier. .

vandiesel · 09-06-2020, 10:22 AM

Thanks Brian!

REF · 09-06-2020, 11:01 AM

Check your connections, unplug and plug the harnesses back in. Just for clarity, you may have posted a response for this in the other thread pertaining to upgrading alternators and the missing secondary jump or exciter wire input on the new units? But....might this be the cause?
I have yet to install my new alternator, might try to tackle it today.

vandiesel · 09-06-2020, 11:43 AM

Is a remote bridge rectifier an option anyone has explored?

I found a strong recommendation for it while figuring out my situation.

carringb · 09-06-2020, 12:05 PM

Quote:

Originally Posted by vandiesel

Is a remote bridge rectifier an option anyone has explored?

I've never done one of those, but I read a while back this was popular for Ambulances, and it works better simply by nature of separating the major heat sources, plus it allows for larger diodes, and a dedicated cooling fan becomes feasible at that point.

I explored it on my wreckers a while back, but it turned out the DPFs barely lasted longer than the alternators, so we had to ditch the ditch the Dodge chassis anyways.

vandiesel · 09-06-2020, 08:37 PM

So if I have a bad diode but I’m still getting 14.2 volts at the scanguage am I in imminent danger of failure? I’m concerned I won’t be able to get much in the way of parts before I take off Thursday.

carringb · 09-07-2020, 08:45 AM

Since you still have good voltage, you are probably ok. Modern alternators are 3-phase, so if you lost 1 diode, you're effectively at 2/3 the rated alternator output. If you had a stock alternator, I'd recommend not driving. But the Nations 270 amp is rated for 200 amps at idle (180 hot), which means that even at 2/3 output, you're still getting more juice than a stock alternator at high-idle.

It might be a good idea to also check the PCM voltage as full electric load (lights, A/C on high, any house loads) and make sure it isn't dipping enough to starve the FICM.

Lastly.... I'd recommend testing your battery voltage at idle, and double check your battery connections, in case they are loose enough (or coated in too much anti corrosion spray...) to cause a no-charge condition but making enough contact to still crank. Since the PCM is effectively in-between the alt and batts, ScanGauge voltage won't tell you if there's a battery connection problem.

vandiesel · 09-07-2020, 03:13 PM

Called FICM repair and ordered a leece neville 230amp alternator. I will arrive the day I leave but will be peace on mind. The 370 XP is over $1000. That would be nice but I feel like I have the backup I need with 4 house batteries and a way to join them for non engine power needs. Van life gets complicated ya know.

vandiesel · 09-07-2020, 07:10 PM

Quote:

Originally Posted by REF

Check your connections, unplug and plug the harnesses back in. Just for clarity, you may have posted a response for this in the other thread pertaining to upgrading alternators and the missing secondary jump or exciter wire input on the new units? But....might this be the cause?
I have yet to install my new alternator, might try to tackle it today.

Did you take it on?