ADP Unit Heater Repair

The gas valve may be faulty and has to be replaced. Check the polarity and make sure the unit has a good ground. If setup for Propane, the inlet gas pressure switch my be open. Ensure inlet pressure is set per the rating plate. If pressure is good change the switch.

Make sure 120 volts are present at the transformer (black & white) wires. If not, check the supply power. If there is, check for 24 volts across the (blue & yellow) wires. If 24 volts are not present, then the transformer is bad.

Turn thermostat above room temperature. Thermostat wires should be connected to the “R” terminal and “W” terminal on the control board.

If the exhaust blower does not come on, check for 120 volts at the CMB terminal on the control board. If 120 volts are present, replace the motor, if not replace the board.

Check to see if the pressure switch is opening during operation. If so, check pressure going to the pressure switch. If it drops down below the switch setting, inspect the tubing for cuts or nicks an clean out the barbed connecters on the exhaust blower. If pressure does not drop to switch setting and the pressure switch is opening, then the switch is bad.

Ensure the gas valve is in the on position. Check the spark igniter gap. It should be 1/8″. Some LP models have an inlet gas pressure switch mounted on the gas valve. Refer to the installation manual and make sure the gas supply pressure meets the minimum requirements. If it does, purge air out of the gas supply line. Are 24 volts present at the valve? If not, replace the board. If 24 volts are present and the valve will not open, then the transformer may be to weak to handle the load.

Gas pressure must be set according to the rating plate. Heater must have a good ground for proper ignition and flame sensor operation. Check to see if the flame sensor is cracked or grounded. Check the sensor wire for continuity. Ensure proper flame current signal from the flame sensor. Flame signal should be at least .6 micro amps.

There should be 120 volts at the ACC terminal on the control board, if not the board is bad. If there is, then the fan motor is bad. Fan motor neutral wire not connected to the supply voltage neutral.

Ensure the manifold pressure is set per the installation manual. If manifold pressure is correct, replace switch with part number 65361900. Visually check for proper flame at heat exchanger inlet.

Make sure the tubing is connected to the pressure switch and the exhaust blower. If it is, inspect it for cuts or nicks. If the tubing looks good, replace the pressure switch.

If the pressure switch is closed before the exhaust blower comes on, replace the pressure
switch.

Unit was wired incorrectly. Refer back to the kit instructions. Limit circuit and pressure switch circuit may be cross wired.