Customer Questions and Answers for Heater Assembly by Bosch

Hi Timm. Per your description I presume it runs with water but does not heat. Then remove the front panel and look for the 2-large wires together on the board. Let it fill with hot water and verify incoming water at the sink is at least 120° while filling. Select heated dry. Then let the unit run for at least 10-15 minutes. Use a volt/ohm meter part # MA-DM1 to assist you in your diagnostics. Insert your red meter lead at the control board terminals and see if there is 120 vac output as the black meter lead will be on chassis ground. If there is no voltage output from the control board then stop operations and see if there is a open solder joint on back of the control board. If so then replace the control board part # 00186923. Then disconnect the wires from the board. Select ohms scale on your meter. Place the red meter lead into the wire connector itself and test for ohms as the black meter lead is on ground as well. If there is resistance then the thermal fuse and the heater part # 00480317 circuit is good. Along with the wire circuit connections as well. If not then you access each component itself and with the wires disconnected, ohm each component. The thermal fuse needs to be closed -0 ohms. If open (infinity) replace it. The heater should read 11 ohms =/-10% tolerance. Make sure to test the heater ohms to ground as well for a short (0-ohms). Thank You.