DEF system performance in Sub-Zero temps

[H3LZSN1P3R]

Sounds like a fuel issue, definitely not a DEF issue as DEF won’t immobilize a truck without a warning.

From the owners manual on the block heater. Nothing in there about the DEF heater because it’s passive to the operator when it freezes.

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It was colder than -29°F in West Yellowstone last night, we saw -35°F.

I’ve started multiple times without a block heater below -20°F, even once without a grid heater, but they aren’t super happy.



When I DD’d my truck it was plugged in every night on a timer for 90 minutes (which I found got temps to 90% of being plugged in overnight). Generally the grids never fired.

I found a huge difference with a winter front installed vs not having one installed.

I was plugged in overnight the last two nights at -27°F and -35°F and had a WTS both mornings. No wind, but also no winter front. ECT was low 60’s after starting.

I always have the winter front installed come October. We had 30mph winds and -20°F coolant temp was at 30°C like it always is with the block heater but still got the WTS but that wind is brutal lots of big snow drifts on the road too lol

 

[AH64ID]

I always have the winter front installed come October. We had 30mph winds and -20°F coolant temp was at 30°C like it always is with the block heater but still got the WTS but that wind is brutal lots of big snow drifts on the road too lol

I usually have it on, but was towing recently and it wasn’t cold enough to tow with it on.

 

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