2024 2500HD Gasser Doesn't Charge in Park!

jake111 · 2024-10-29T19:08:35Z

Put my old slide-in camper on new truck. Didn't seem to be charging camper battery. Hmm, didn't seem to be charging truck battery either. WTF? Took it out for a spin and slowly it came up to 14v on the dash gauge (couldn't check camper while driving, you know). Idling in driveway, no charging anything. 2000 rpm, no charging. You must be kidding!! Finally found that if I put it in Neutral, it slowly came up to 14v, even at idle. Why would some clever GM engineer think this was a good idea?

Maybe others can verify that they all do this, or if it's just my truck.

jake111 · 2024-10-29T21:38:59Z

More... well, I guess it will charge in Park . . . sometimes. If I turn on the headlights and let the battery run down a little, then start the truck, it starts charging (although under 14v).

So I guess it's ok. But if you have a camper or trailer attached and want to check that the truck is charging the house battery, you might have to shift to Neutral to check (with parking brake set and somebody sitting in the driver seat to make sure it doesn't roll away).

Wxman · 2024-10-29T23:55:41Z

Have you experimented with the Tow/Haul mode? I think it is supposed to boost charging voltages. Don't know about the idle/park/neutral stuff.

Another JR · 2024-10-30T03:21:35Z

Welcome to smart alternators! It is designed to properly power your truck electrical system and recover your start battery while reducing accessory drag when high output is not needed, but it isn’t ideal for parallel charging a camper battery with 50 to 60 feet worth of wire losses, especially at idle.

The proper solution is a DC to DC charger such as the Victron Orion series installed at your camper battery. While they cost a bit over $200 for a 30 amp charger and you’ll need to run 6 awg positive and negative wire for the whole run, the good thing is you will already be set up for a lithium battery conversion if you decide to do that.

jake111 · 2024-10-30T05:02:30Z

Obviously, I live in the past. In a discussion with a friend, we speculated that maybe it had something to do with getting better EPA or mileage numbers, by shutting down the charging system when not needed. The tow/haul comment by Wxman above got me looking around.

I just looked through the owner's manual (digital version so I could search). No mention of tow/haul doing anything to the electrical system.

Searching the 'net showed "Regulated Voltage Control" on some old models. Sounds likely even if the name has changed. To overcome the problem, the suggestions were to either (1) turn on tow/haul, or if that didn't work well for your application, (2) turn on headlights.

I think the important thing is to be aware of this. I will be satisfied to know I can adjust whatever I need. While driving, so far the dash gauge seems to sit mostly at 14v (I only have 500 miles on the truck). But if it doesn't stay there, just turn on the headlights or t/h.

That still doesn't explain the difference between being in Park or Neutral, but there are a lot of things that can't be explained (don't get me started!).

Thanks for the replies!!

Another JR · 2024-10-30T17:21:05Z

Do you have the base 170 amp alternator?

bruceb58 · 2024-10-30T19:21:12Z

I have a 50A Victron Orion DC to DC in my trailer. Sometimes I need to turn on headlights or seat heaters to get the alternator voltage high enough to allow the Orion to start. Once it starts, it puts a high enough load on the alternator to keep the voltage high without having lights or the seat heater on.

Another JR · 2024-10-30T19:43:26Z

18 minutes ago, bruceb58 said:

I have a 50A Victron Orion DC to DC in my trailer. Sometimes I need to turn on headlights or seat heaters to get the alternator voltage high enough to allow the Orion to start. Once it starts, it puts a high enough load on the alternator to keep the voltage high without having lights or the seat heater on.

I have not had that occur with my 30 amp Orion. It just comes on after the programmed delay period after truck start. I have the 220 amp upgrade alternator and ran 6 awg wire. The total wire length for positive and negative is just under 60 feet.

What wire gage do you have running to the 50 amp Orion?

lineman1234 · 2024-10-30T20:37:36Z

I just took a pic today, its in drive sitting but is the same in park or neutral. . Its charging, as when the batts are happy its much less on the meter.

As i have my front/rear dashcam always on, it uses power overnight or parked, i do have a second batt installed. It will charge just a little more on the meter as rpm goes up, but little. As needed it will charge, drop when both batts are happy.

Same thing towing the camper, as needed it will charge the camper batts, through the one way diode on the camper charge wire, as needed, then level off and repeat as needed as i have a DC freezer in the rear kitchen always going and whatever is on for camper load like the gas detector.