Pull the blower motor out and check both the motor, the blower wheel and the housing for any trash that may be stuck in it................
possible clogged or damaged heater core
The belt has worn on the edges and creates friction which causes squealing. Also, sometimes when a belt is cold it will squeal.
The heater might blow cold air in a 2000 Silverado because the thermostat is sticking and not changing from cold to heat. The thermostat is usually located in a hose that leads from the radiator to the motor.
The heater may not be on - but the fan still blows air through the vents when they're open !
Check piping. Make sure cold line going into cold side of water heater and hot side coming out hot side. Cold feed for water heater should come off main cold line. Make sure valves are open to and from water heater.
You may need to add water to your cooling system.
It is probably your thermostat. That will make cold air come in. It's probably stuck open. The part is only about $4.00 at Auto zone.
Heater core (radiator) needs to be cleaned or changed
My central heater will not come on while the pilot is lit,The heat does not kick on.
no.....the heater would have to be leaking
You will get some back pressure from the water heater. It will come out of either the hot or cold. Shut the tank off if there is a shut off there.
By Andreina Urdaneta A clean water heater will heat and maintain water better and last longer. Once a year, flush your water heater, and in extreme hard water areas, at least twice a year. If you feel up to the challenge, here are some tips to help you in a basic cleaning. 1 Turn the water heater and the cold water supply to the water heater off. 2 Hook a high-quality garden hose to the drain valve, and place the other end in an area where hot water will not cause damage. 5. Open the drain valve. 6. Disconnect the cold water pipe on the top of the water heater. This step will let air into the water heater so it will drain. When the water heater is empty, close the drain. 8. Pour tile cleaner into the cold water, leave for a couple of hours and drain the detergent out of the tank. 10. Reconnect the cold water supply to the water heater. Open the cold water valve and let the water heater flush for a couple minutes. 12. Close the drain valve and open the hot water faucet nearest to the tank, and let the water heater fill. 13. When water starts to come out of that faucet, reopen the drain and let the water heater continue to rinse. After all the air is out of the water heater, turn it back on. Take care of your water heater, and it will take care of you. If you keep ignoring the task, your water heater may just leave you in the cold.