DEF freezing

DavidEM

Member
I understand that DEF (diesel exhaust fluid) used on Mercedes diesels freezes at 12 F. Apparently there is a DC heater on the fluid container and its piping system to prevent that. Is the DEF heater system thermostatically controlled so it doesn't use much energy until it gets cold outside?

We will keep our Winnabago View in an unattended, unheated and no electricity storage lot for the winter in Connecticut. How do I keep the DEF from freezing?

I don't really want to use the built in heater as that will run my chassis battery down. And there may be more parasitic loads than the DEF heater that will run the batteries down. I understand that disconnecting the chassis battery will require all sorts of resetting of things when it is powered up in the spring.

So what do I do. I guess I can use the solar panels to keep both house and chassis batteries charged. Will that do the job? This will be winter light conditions in Connecticut, probably half of the solar input than in summer.

David
 

TJLee089

2013 Itasca Reyo 25R
I can tell you with absolute confidence based on 7 years of storage, outside, at temps that go below 12F every winter, with no hookups or solar, that this is not a problem. If the DEF freezes, it simply thaws when the temps rise with no deleterious effects.

See here for more info.
 

DavidEM

Member
I can tell you with absolute confidence based on 7 years of storage, outside, at temps that go below 12F every winter, with no hookups or solar, that this is not a problem. If the DEF freezes, it simply thaws when the temps rise with no deleterious effects.

See here for more info.

That is what I was hoping would be the case.

David
 

lindenengineering

Well-known member
I have advised many times to keep the tank full.
This ensures that the heater which sits fairly high up in the cartridge is always submerged even if it is frozen.
If the tank is only partially full, the heater may not be fully submerged so it overheats and often burns out.
In any case with a part filled tank and a frozen fluid stack situation it might all be working as it should but with a frozen liquid which cannot be pumped, so the system doesn't reduce NOx then the count down light comes on.
We had three such "visitors" last week with this scenario! A fill and reset & it lights out and glee!
Don't get caught it your level down!
It can be expensive at about $1500 to fix if the heater goes south.
Dennis
 

DavidEM

Member
OK, it seems that you are saying to keep the tank full so the heater can work properly. But do you have to heat the tank for long term unattended cold storage? That obviously means keeping the chassis battery connected. How do I keep it charged?

David
 

DavidEM

Member
If it's like the heated mirrors, it only heats while the engine is running.

--dick
I have my doubts about that. If a commercial Sprinter were left unused over a weekend in Minnesota with overnight temps in the -20s the DEF would freeze. Then when you start it up in the morning the DEF injection pump would fail due to trying to pump frozen DEF.

David
 

Ciprian

Spark Plugs not allowed!
I wouldn't worry. The pump will not pump until the DEF thaws out, at least enough of it to be able to pump, along with the lines. Don't over think it. Like Dennis said, fill the tank up, park it and then forget about it.

Sent from my moto g(7) using Tapatalk
 

Benagami

Member
The 12v battery only has enough juice to run a heater like that for a few hours. The DEF heater absolutely shuts down the moment the engine is turned off.
 

TJLee089

2013 Itasca Reyo 25R
I could be wrong, but my suspicion is that if starting up with the DEF tank frozen, the engine simply runs without DEF until the tank thaws. Obviously, starting at 12F or lower is common for commercial vehicles. I agree with others: don't overthink it.
 

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