Freightliner Cascadia '20 bunk heater not heating

You truck must have the park smart system. I can see the button on temp setting. You have to push button on temp setting it should turn orange. Your truck probably has Optimized Idle or EAPU. You turn on Optimized Idle and the computer will turn on the Orange light on the temperature setting in the sleeper and you turn on the fan speed in the sleeper and it should turn the heat or a/c on depending on the temperature you set it for.

 

The button is like on/off switch for the Electric a/c and diesel burning heater. When Optimized Idle is turned on at the front dash. The light in sleeper should come on automatic. That's how it work in my 2020 freightliner. My truck has the electric APU. It's 8 batteries in total. The sleeper has a separate diesel burning coolant heater. It heats the coolant and keep the engine at 150f. That how is heats the sleeper also.

Then is has electric a/c for sleeper both system will run about 6-8 hours on the batteries. Then engine will start automatically to recharge the batteries. If you turn on Interior Comfort Mode. It will Start the engine to heat or cool the sleeper faster. Then shut off and run on batteries.

Truck has 4 batteries under driver side seat like normal. Then you can see box behind sleeper that holds 4 more batteries

 

This is the electric a/c part on back of sleeper

 

Have changed my info a little. When you turn on Optimized Idle with or without Interior Comfort Mode. You should see this with the sleeper fan off

When you turn on sleeper fan the Park system will light up and you should hear the electric a/c or the heater should fire up and blow some heat. If the engine is cold the heater has to heat the coolant first to get some heat going.


The only downside to the system is it only blows heat or a/c in the sleeper. If you turn on Interior Comfort Mode. When the computer starts the engine it will blow heat and a/c out the front dash vents at the same time.

 

Not sure what you mean when saying Optimized Idle is off when is engine is off. You have to turn the ignition key on and leave the key on all the time. The dash lights and stuff will be on all the time. Optimized Idle let's the computer start at stop the engine automatically. Optimized Idle will start the engine if the batteries get down to 12.1 volts. It will also start engine to keep engine oil warm. You turn ignition key on and leave it on. You don't have start the engine. You turn on Optimized Idle, now the computer has control of the engine.

Then you go in sleeper and turn the temperature all the way to hot and turn the sleeper fan on high and see if blow hot air out. Look at the engine temperature on the dash. If it stays at 160F you should have heat in sleeper. If it won't hold at 160F the heater probably is not firing up. You should be able to feel hot air coming from vent/exhaust pipe on back of sleeper on the out side. You can also hear the little fuel pump click click clicking as it's pumping fuel from tanks into heater from outside.

Maybe the heater is not firing up. It burns Diesel soot builds up inside them and the won't fire up. If you turn on Interior Comfort Mode on the front dash screen for Optimized Idle. That should start the engine when you turn sleeper heat and sleeper fan all the way up.

 

Sound like the heater is not firing up because it also won't keep the engine warm. I would just turn on Interior Comfort Mode, like you did. Then let the engine keep you warm. Your truck if the same as mine. Now has 2 a/c unit and 2 heaters. You have the regular a/c on the engine and the regular heat from engine. Then you have the electric a/c unit in the sleep and the diesel burning heater under the sleeper.

This might help you understand the system better. Detroit Diesel had Optimized Idle back in the 90s. That setup just used the regular engine for heat and a/c. So when sleeping at night the computers would start and stop the engine all night. Many drivers did not like that. So they did would just Idle the engine all night. That was normal back then.

Then they started to put diesel burning heaters in the sleepers. They could run all night but that did no solve the sleep a/c probably in the summer. So driver still would idle trucks all night. Today they have Electric a/c in sleeper when parked and the diesel burning heaters and extra batteries to runn all the for 8 hours when parked.

When you had/have Interior Comfort Mode on it will run the engine more if the bunk diesel fired heater or the electric a/c is not working. You won't have the benefit on the newer electric a/c or sleeper diesel burning heater. You just have the basic system like in the 90s. The engine will idle more depending on how much heat or a/c you need. Your electric a/c might work fine and just diesel burning heater won't fire up.

That's why the engine keeps running even if that batteries are fully charged. It's trying to keep the sleeper warm or cool depending on the temperature you set in the sleeper.