Radiator Repaired, Now heater won't work.

I recently had my transmission and radiator repaired and now my heater doesn't seem to be getting very hot. I've also noticed that the Temp. gage seems to stay very very low, no matter how long I drive. And, ever since my car was in the shop my Day Time running lites won't work. The mechanic swears up and down that these are unrelated problems. Can anyone tell me what happened? Hi:

Sounds like there may be air trapped inside the cooling system causing your heater not to function properly. Driving the car should work out the air. But, once this happens, your cooling system will be low on coolant. You should check your cooling system for low coolant Car Repair Talk's forum.