No Heat, when towing..
 

I was towing our boat to storage yesterday, temp was 39 degrees, so I turned on the heat. The blower worked fine, but no heat, it would only blow cool air. After unplugging the trailer, the heat was back to working like it normally did. Obviously I have something going on with my wiring on my trailer plug. But what..Bad ground??
I usually don't tow much in cool weather, so I had never noticed the heat not working while towing, but the A/C always worked flawlessly during the Summer.
Anyone else experienced this? Thanks for any info.
Rick

I would highly doubt an electrical problem.

Last time that happened on my 2010 it was a blown head gasket. I think my 2007.5 6.7 is doing it now too.

Chris

Check your coolant level.

I just fully serviced the Truck for a trip to Florida in the coming weeks. All Fluids are fine. Engine temps are normal, while empty and towing. Heater was working when I drove it this morning. Anyone else have any ideas? Thanks

Did you look at the coolant level since you towed with it?

If you don't have a blown headgasket, or a low coolant problem, then most likely, it's going to be a dealer problem on the electronic side of things.

Check the coolant.

Chris

Might have an air bubble in the coolant system. There should be a high point bleed on the passenger side right by the egr cooler. Black stub sticking up with a silver allen head plug in it.

Yes, coolant check was the first thing I looked at. There's no sign of coolant leaking in the engine bay or around the Head, no sweet smell from the exhaust and engine temps are normal. She runs strong as ever. I still think it was an electrical klitch with the trailer plug. Maybe somehow not allowing the blend door to open to heat side and stayed open to drawing outside air. I had turned the heat off when I plugged in the trailer, after about five miles or so I turned the heat up and that's when it only blew cold air. I currently don't have a trailer around to test this phenomena and see if I can recreate it. Eventually,I will hook up again and see if it happens. As of now all is working normally. Thanks