no hot air

my heater only blows out hot air after the car is moving even though the temp gauge shows normal

With the car cool, check to make sure the radiator is full up to the bottom of the cap. Then check to make sure the reservoir is at the proper level. If it is real low, you may have to do this a second time. If it is low, you probably have a leak somewhere. It should be found and fixed so you do not blow up the engine. What happens, is that the heater core gets robbed of coolant, and you do not get heat. But, when going down the road, enough coolant gets sloshed around and passes into the core to get some heat. I quite frequently see low coolant do this, and the gauge still looks fine. Give it a look!!

With the car cool, check to make sure the radiator is full up to the bottom of the cap. Then check to make sure the reservoir is at the proper level. If it is real low, you may have to do this a second time. If it is low, you probably have a leak somewhere. It should be found and fixed so you do not blow up the engine. What happens, is that the heater core gets robbed of coolant, and you do not get heat. But, when going down the road, enough coolant gets sloshed around and passes into the core to get some heat. I quite frequently see low coolant do this, and the gauge still looks fine. Give it a look!!

Agreed.

If the level is fine, with the engine at full operating temp, feel the heater hoses going in and out of the heater core.

If both are hot, the dash control may have failed or a vacuum line is broken, and it's not selecting heat.

If one is hot and one noticeably cooler, check the operation of the heater control valve to see if it opens when you select heat.

If the valve cycles properly, the core may be clogged...you can try removing the hoses and flushing it...but they are usually hogged up with rust, and start leaking once you get them opened up...:uhoh: