Heater not very hot

Today was our first night to get cold enough to leave a good coat of frost in the wind shield on my 2008 Chevy Silverado 1500 (50K miles). So I started engine while I went back into house for a few things. I thought it odd when I got back that it had not cleared much. I so scraped it and drove off. Its a 5 mile drive to work, and the heater took a long time to blow warm air, and it never did get as warm as it has in the past. Anti-freeze level is good, the dash gauge shows normal and no anti-freeze on the drive. Where should I begin looking?

Feel the hoses that run to the heater core - they’ll run to someplace on the firewall. If both of them are hot then you probably need to look at the blend door and its controls (interior behind the dash). If both hoses aren’t hot then you’d suspect a clogged heater core.

That is all assuming that your blower is actually blowing well.

You might also get a read on the actual coolant temp (an infrared thermometer is a quick way) - just to make sure its not actually running cool while your gauge is misreporting.

Some cars have a water valve in line with the heater core. If you have one, make sure it opens.

Do you have an engine temp gage or just an idiot light?

If you have only a light, try checking the upper and lower heater hoses to see that they’re both warming up. The thermostat’s sole purpose in life is to allow the engine to rise to full operating temperature and staty there. If yours is stuck open, you’ll get no heat from the heater. This will also not trip a Check Engine Light, as it’s not a monitored device.

If you have a temp gage and the engine is staying on cold, your T-stat is probably stuck open.

If the engine’s cooling system is working fine, then check the heater valve that markmast referred to. You can check it as suggested by Cig, by feeling the heater hoses.

If all of that is good, then your blend door is stuck.