Odd coolant temp change

[Lucky Jeff]

My boss has an 01, lately on his way to work, and on his way home from work. He gets about 2/3 of the way there and his temp will all of the sudden drop all the way down almost to 140 and start blowing cold air out of the ducts. Sometimes it comes back up, sometimes it doesn't. My tstat was recently stuck wide open and would atleast get up to 160 and still blow out warm air. So I'm not sure what's going on with his truck oke:

 

[BgBlDodge]

Change the t-sat out. Cheap and easy. I would get it from dodge though. It's like $50 from them but it seems to be the best one to get.

 

[Rob_Bones]

I just had to replace the t-stat in my truck, only because it was leaking around the seal. I got a 190* one from Napa, it was only $27 and the Dodge dealer wanted $80. They look and function the same. If his heater won't operate its most likely due to lack of coolant in the system. If his radiator is full he must have some sort of a blockage somwhere or his water pump might be shat'n the bed. I also did the water pump on my'n not to long ago and it too was pritty cheap from napa, for a new pump it was only $60'ish.