Low voltage/battery light indicator

[Gunny7156]

Discovering new issue 2025 Ram 2500 w/6.7 Cummins. Been experiencing well below 0 outdoor temps here in PA (-15 to -20). If I remote start my truck to warm it up, on 3-4 occasions, I've noticed that my voltage indicator is down to 11.2-11.3 volts. I also get a low battery warning indicator illuminated on my dash. To my surprise, she has started every time even without having the engine block heater plugged in. Once I get in the truck, I start/disengage the remote start feature and within a few minutes, the voltage will climb to a normal operation and low battery indicator goes out. The only things that are "running" under the remote start is the heated steering wheel, heated drivers side seat, heater/defrost and rear window defroster. What I am discovering is, after playing around turn different things on and off, if I turn off the rear window defroster, my voltage is climb to as normal 13.5 volts, and battery light will go out. Heater/defrost and heated seats don't seem to change or increase the voltage on the dash. Several questions, Is there a short in the rear window defroster? Is there a way to disengage the automatic turn on of the rear window defroster under the remote start(I can't find anywhere to do that)? Weak battery (s)? Or is this normal? My son has similar truck (2024 Powerwagon with 6.4 hemi) and he only looses about 0.1 volt with rear window defroster on. I'd love to have a dealer look into this but the outdoors temps have increased to above freezing and I'm not experiencing the low voltage issue for the dealer to replicate. Thanks in advance for any help. Tried to post video showing how much voltage I'm loosing by turn rear window defroster on and off but can't post video.

 

[Dean2]

On our pickups, depending on trim, the rear defrost also turns on the heated driver and passenger side mirrors. So it could be any one of those that is pulling that much juice. The draw you are getting is not normal. One thing that confuses me, if you turn on rear defrost with the switch on the dash, does it cause the same issue, or only at remote start. Also, the fact you are pulling so much juice only in cold is odd.

While the vehicle is running in remote start mode, turn off the rear defroster. Then step on brake and hit start button. Shut off vehicle, restart remote start, the rear defroster should not come back on. This is true of any other adjustments you make while the vehicle is in remote start running mode. They should be remembered for the next remote start. as you probably know, the max defrost front and rear on remote start only triggers at temps below 40F.

Read this link from a couple of days ago, and refer to your owners manual, there is a few of the pages from the 2025 owners manual pasted into the link. It will help you a lot.

Remote starter. Love it, but there is something odd

Happened twice now. I remote start the pickup, then load the bed and go find the dog to put her in the crew cab. Open the door and the fans are running at max. Fan controller at the consule is set at minimum. The fan never does anything odd when I start the truck from inside sitting at the...

www.ramforum.com

 

[Gunny7156]

On our pickups, depending on trim, the rear defrost also turns on the heated driver and passenger side mirrors. So it could be any one of those that is pulling that much juice. The draw you are getting is not normal. One thing that confuses me, if you turn on rear defrost with the switch on the dash, does it cause the same issue, or only at remote start. Also, the fact you are pulling so much juice only in cold is odd.

While the vehicle is running in remote start mode, turn off the rear defroster. Then step on brake and hit start button. Shut off vehicle, restart remote start, the rear defroster should not come back on. This is true of any other adjustments you make while the vehicle is in remote start running mode. They should be remembered for the next remote start. as you probably know, the max defrost front and rear on remote start only triggers at temps below 40F.

Read this link from a couple of days ago, and refer to your owners manual, there is a few of the pages from the 2025 owners manual pasted into the link. It will help you a lot.

Remote starter. Love it, but there is something odd

Happened twice now. I remote start the pickup, then load the bed and go find the dog to put her in the crew cab. Open the door and the fans are running at max. Fan controller at the consule is set at minimum. The fan never does anything odd when I start the truck from inside sitting at the...

www.ramforum.com

Appreciate the input and I'll have to try what you suggested to disengage the rear window defrost during remote startup and see if that turns it off for the next remote startup

 

[crash68]

Been experiencing well below 0 outdoor temps here in PA (-15 to -20).

Not sure if your quoting wind chill or actual temperatures, the -15 to -20 seems a bit cold for your area.Vehicles are not affected by wind chill factor.
The truck should be able to start well into the double digit negative temperatures with proper winter blend or treated fuel although Cummins recommends to plug in when the temps drop below zero. The engine and yourself will both appreciate using the block heater.
As for the current draw of the rear defroster, you could unplug the connector at the window to determine if it's the window or mirror defroster causing the issue.
Keep in mind even though the engine is running the glow plugs can still be energized to aid in heating the combustion temperature up(the same applies for trucks with grid heaters).