I have a 2003 Caravan and I noticed this morning that when I turned on the heater the Temperature guage drop signifigantly and when I turn the heater off the Temp. jumps back up. It's still within the normal range when this occurs. Is this normal? I'd appreciate any input before I take it to the stealership.
Thanks in advance

 

check your coolant level it could be low do it with the heater on but don't open the cap look at the overflow tank