Aux heater issues

[fwiz]

In troubleshooting my non-operational under-couch aux-heater blower-motor:
I found that my engine coolant system runs rubber hose up to the rear of the couch. Then it transitions to copper lines which run to the under-sink area. There, it transitions to rubber again and connects to the... water heater?!
On the water heater: in addition to the fresh water supply inlet & output; There are fittings on the lower left and right of the water heater which are attached to the engine coolant line, then the hose runs from the under-sink water heater to the aux-heater-core under the couch.
I'm baffled, could this water heater have its own heater core which allows engine heat to heat the water supply?
I am fairly new to RVing, and have not heard of such an animal. I searched this forum, but found nothing that helped.
There is no mention of this system connectivity in the manuals. Please explain to me what type of equipment/system I am dealing with.

Also, In assessing the blower motor: I am seeing a short between both positive leads of the motor and ground. continuity betweeen everything. So... bad motor?

Thanks.

[RivetED]

Originally Posted by fwiz

Also, In assessing the blower motor: I am seeing a short between both positive leads of the motor and ground. continuity betweeen everything. So... bad motor?

Thanks.

With DC, after any capacitance &/or inductance in the circuit has been overcome, or 'timed out', a short is what you will read on a VOM. Only the most sensitive Digital V.M.s can help you there...a motor coil or winding (depending on the exact position of the commutator & brushes) is nothing more than an inductor (L) which will read 'dead short' after it's 'RL charge time'...very short, milli-seconds, under most conditions.

[cooperhawk]

You are correct in your assessment. The engine coolant lines run through your auxiliary heater and through your water heater. This allows you to have warm water while you travel without having to turn on the propane to heat the water, also to have additional heat other than dash heat.

[74Argosy24MH]

The heat exchanger in the water heater is a motor aid, very handy for instant hot water as gunner said. While you are working on these check your heater hoses. If they are original they definitely need to be replaced. A break will dump the engine coolant in less than a minute, if you are lucky it will be outside not into the carpeting.

John

[87MH]

On the water heater question - be aware that, depending on the circuit board in the water heater ignition system, you may not be able to get a "burner lit" indication in the coach when hot motor coolant is circulating - the many of us see normal motor coolant temperatures of 205 to 215 degrees!

The water heater may actually have to "cool down" before the burner will light.