If you think your heater is faulty here are two simple tests that can be done before returning to the manufacturer.
2. If the above multimeter test proves successful a simple water test can then be conducted. Please watch the video carefully. It is essential that the heater is “primed” with water before submerging in the tank. Once “primed” DO NOT allow the water to drain out. Keep the inlet fitting capped until you turn the heater on.
CAREFULLY FOLLOW THIS PROCEDURE
1. Prime the heater full of water using your finger to block leakage from the inlet hose.
2. Submerge the inlet hose into the water tank without allowing any water to escape.
3. Turn power on and remove finger from inlet hose. (this is to be done very quickly after turning power on!)
4. Heater should begin to “cycle” water.
5. Gently restrict the water flow by covering with your finger.
6. You should start to feel the water get warm on your finger that is restricting the flow.
7. Remove the water restriction. (the first “gush” of water should feel warm as it has been heated.)
8. Turn heater off.
CAUTION – DO NOT LET ANY PART OF THE HEATER BECOME SUBMERGED IN THE WATER.
If this test has resulted in the heater “cycling” the water and heating the water, the heater is in good working order.
If the heater was not working when installed in the car it probably had air in the system preventing correct heater operation