cooling system help needed

[silvertdi]

I've got an '81 rabbit diesel. I recently replaced the head gasket, but ever since I've had the car it's done some funny things. Here's what it does, I need your help. Once it's up to operating temp, I turn the heat on and the coolant temperature goes up a bar or two. I turn off the heat, it goes back down. Opposite what I would expect. Also, the heat is not hot, only warm. There is no air in the system as it's been running for some time since the head gasket exchange. The water pump is new, thermostat is new, new hoses, new expansion tank cap. I just bought a new expansion tank as I've seen coolant around the seam in the expansion tank. Any suggestions?
Also, I've noticed that heat is not affected by the blower motor. I'll turn the heat on and turn the van all the way up, the vents will blow cold and the floor and speaker grilles will blow warm. Is this right. Seems like the car would never get warm in the severe cold.

Thanks for your help.  

[jtanguay]

weird problem.. i suspect the blend door and some linkage issue for the heat problem..

did you refill your own cooling system?  how was it filled?  i remember when filling my system, i had a nice airlock in it.  rad stayed cold, engine temp was rising pretty high.  probably at the 100-105C range (rad still cold) so i was scratching my head... came here and some people told me that i should have filled it by filling the rad first.  so what i did was run the car without the rad cap and wait for it to get up to temp.  so i did, and voila!  rad got hot when it reached operating temp, and that was solved.