It won't circulate until the engine is hot. Also: Squeeze the suction hose (bottom hose)from the radiator to the pump, it should have a metal spring inside to keep it from collapsing. The spring may have rusted out and the hose is collapsing upon suction.
First check the water level. Low level will not get to the heater core. Change the thermostat. If you recently changed the thermostat, bleed the coolant system.
MY CAR WAS DOING THE SAME THING NO HOT AIR COMING OUT OF THE HEATER I CHANGED THE THERMOSTAT. IT WASNT THE THERMOSTAT. I GOT TO CHECKING AND THE SEAL IN THE WATER PUMP WAS BAD. I REPLACED THE WATER PUMP AND IT WORKS FINE NOW.
To replace the thermostat on a water heater, first turn off the power and water supply to the heater. Remove the access panel and insulation to access the thermostat. Disconnect the wires and remove the old thermostat. Install the new thermostat, reconnect the wires, and put everything back together. Turn the power and water supply back on and test the water heater.
water pump may not be worn out, heater core may be clogging
The function of a gas water heater thermostat is to control the temperature of the water in the heater. It does this by sensing the temperature of the water and adjusting the gas flow to the burner to heat the water to the desired temperature.
Of course a water heater thermostat would be defective as water heaters / hydronic boilers would use an Aqua Stat
To replace a water heater thermostat, first turn off the power and water supply to the heater. Remove the access panel and insulation to access the thermostat. Disconnect the wires from the old thermostat and remove it. Install the new thermostat and reconnect the wires. Replace the insulation and access panel, then restore power and water supply.
water pump
No, BUT they do have an AQUA stat
Someone turned up the thermostat, or the thermostat has failed. The thermostat tells the heater what temp to keep the water at.
To test a hot water heater thermostat, you can use a multimeter to check for continuity in the thermostat. First, turn off the power to the water heater. Then, remove the access panel to expose the thermostat. Use the multimeter to test the thermostat's terminals for continuity. If there is no continuity, the thermostat may be faulty and needs to be replaced.
To replace an electric water heater thermostat, follow these steps: Turn off the power to the water heater at the circuit breaker. Remove the access panel to expose the thermostat. Disconnect the wires from the thermostat. Remove the old thermostat and replace it with a new one. Reconnect the wires to the new thermostat. Replace the access panel and turn the power back on. Test the water heater to ensure it is working properly.