Volvo sleeper having some electrical issue. New batteries as of January, truck drops from 14.4V to 10.1V when I shut the engine off...the buzzer in the sleeper beeps after 5 minutes so I press the "fan-down" button to shut off the sleeper blower.
I'd use Idle Smart to periodically restart the engine to recharge the battery but I feel like 10.1V is too low of a threshold...therefore if I were to use Idle Smart the truck would just be on 24/7 to keep battery not at 10.1V. And besides, Idle Smart shuts off anyway after 5min because of engine idle shutdown so I don't even use it.
Bunk heater and fridge malfunction too; they'll work for a limited time before powering down when the truck is off. And when it was working fine the bunk heater got it too hot on the coldest setting...when I had the circle knob at coldest setting in the sleeper the bunk heater got to 75-80⁰F...I sleep at 60⁰F. But, winter is almost over and I'm having to use the A/C to keep at 60⁰F while I sleep...but even the A/C is struggling to keep it cool inside...if it's 80⁰F (like it was in LA/TX last week) it struggles to keep interior cool)...in order to keep A/C on I just push in yellow knob and leave truck running. I let the trailer brakes hold me in place.
The 2000w power inverter will run for 20 seconds before the orange light on it starts flashing and it shuts off...even when the engine is on the inverter shuts off after 20 seconds of microwaving food with a 900w microwave.
Plus, when I'm driving every so often the dashboard lights up every minute with "Light Controle Module in High Voltage Mode" and after a split second that warning disappears.
What could it all be?
Electrical Problem
Discussion in 'Questions From New Drivers' started by PianoManCJS, Mar 4, 2026 at 6:39 PM.
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Something is drawing a lot of power if the new batteries are just showing 10 volts,unless one of them is bad.
I would shut everything off,turn master switch off if you have one then check the voltage,should be over 12 if they're all good. -
Volvos ride like a cloud but they have electrical issues frequently. It sounds like you have possible bad ground wire, check for copper wire from engine to frame or loose connections at alternator, battery, or the device that kind of works like an APU.
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A 12-volt battery is considered fully discharged at 11.0 volts and is unable to recover.
You need new batteries.tscottme Thanks this. -
They are new as of January...
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A loose connection can give lower voltage indications. Voltage is like water pressure, imagine holding a garden hose close to a running water faucet but not screwing the hose fully onto the faucet. The water pressure in the closely-held garden hose would be lower than water pressure in fully screwed-on water hose.PianoManCJS Thanks this.
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Do you know how to use a multimeter and understand basic electrical thingies?
if so, start with the voltage AT THE BATTERIES
if are watching the gauge in the dash, that is not directly hooked up to the batteries, it comes through the ECM, and it could easily be a ground issue with the ECM.tscottme and PianoManCJS Thank this. -
I'll take a look when I get a chance.
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A loose connection ANYWHERE between the batteries and the light on the dash may be involved. Also, a bad ground strap sometimes mimics low voltage, loose connection. The ground strap runs from engine block to truck frame. Hopefully Google can show you exactly where.
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even new batteries die quickly if overcharged and as mentioned above the FIRST thing to check is always ground
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