Last night it got down to 31 degrees and when we got ready to go to church we had no heat in the 2003 E320.
After church we drove for hours around to several relatives delivering Christmas gifts, with out heat.

The blower and everything seemed to work, only cold air came out no matter it it was the defrost or the floor vents.
I stopped at Harbor Freight and for $15 I picked up a 12V defoster/heater that got us through the day.

It used to be always the thermostat when the heat died but today I'm lost with all the sensors in cars today.

Any ideas where to start other than the dealer?

Thanks to all

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1998 Land Rover Range Rover 66K Miles
1988 300SE Totaled in 1998, hit by drunk driver, but we walked away OK
1989 420SEL 140,000, just warming up. Total by 18 wheel gas truck rear ended, but refused to lose another MB. Had it repaired cost $10,000+ Great Car again SOLD it for a 2003 C320 to save on gas
1991 2500 Suburban 454, 130,000, Best truck in the world. SOLD it out right.
1952 8N Tractor 1,000,000-/+