Thermo testing

It sounds like the inlet pipe might be clogged - with something nasty, no doubt. If the water can't flow unobstructed from the heater to the tub, the water at the thermostat might be hotter than the water in the tub, so it shuts down early. Of course, it could just be a problem with the thermostat itself. If you can remove it, you can test it in a pot on the stove - listen or watch for it to open / close, or monitor its connections with your ohm meter. Also, make sure the knob on the controller hasn't been offset. Someone may have removed it, then placed it back on wrong, so that the controller can't be turned up correctly.

You can find replacement parts thru google - I had to do that a while back. No one in town could help me, but I found a company that stocked just what I needed.

You will be inviting us all over, right?

Yea, thought about the filter but it was fine. Knob too. After testing,the thermostat is not opening and closing properly. I have one ordered now,Ill see... Right now working the axel bearings and oil seals on the van while I wait. Thanks again.

I have the impression that the overheat protection of the heater is set to low.

The pump keeps on running but the heater shuts down?

My concern with this would be that the overheat protection should be a manual reset although I suppose it's quite possible that it's a auto reset and happily doing it's own thing in the background whilst the OP tears his hair out tinkering with the thermostat.

A small clickson inside the housing, like a small motor overheat protection, a click but it isn't the thermostat.

Try to measure the resistance of the heater before and after the click. Be carefull with the power lines, unplug before each measurement attempt.

three possibilities

1. flow is restricted,
2. heater is overheating (could result if air is in the line), or
3. the most likely with your symptoms is the control that adjusts the temperature is defective, either an open or short.