After 6 inches of rain. It started to snow and my heater isn't working on my truck. It was blowing warm until I switched it to defrost and then no heat at all. The temp is showing 200 so the truck is at operating temp. Any ideas on where to look to solve this problem. I have an 07 5.9.

 

is the fan even blowing anything??

 

Sorry the fan is blowing in all modes of selector switch.
It's just not blowing any warm air in. I ended up having to stop every 20 miles to scape the windshield due to icing. Where I'm at today's low was only 29 so I can't imagine it was the cold.

 

does it blow heat on any other setting, like to the floor or out the vents...im just trying to eliminate stuff here.

 

High temp and low to no heat= broken blend door or leaking head gasket.

 

It does not blow heat on any setting. If I set it on defrost. It blows were it is supposed to too. Same on all settings. Just no heat.

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It turned out that I was low on water. I had a hole in the lower hose. Replacing it now so hopefully that will be the end of it.

 

Yup, I was going to say check the anti-freeze level. Glad you found it, just have to get all the air back out of the system now.

 

Well it's not the hose. I've replaced the hose and it's still leaking like a seeve. I can't see where it is coming from. Any idea's?

 

What area of the motor?

 

When you look at it from the top you can see a little bit of fluid being kicked up by the fan. from the bottom I can see it dripping from the corner of the oil and water pump/ lower hose area.