"Motor hot water" switch

[Ron Burgundy]

As shown in the pictures below, I have a switch mounted on my 12 volt panel labeled "motor hot water." I have been unable to determine what this is for and there is no mention of it in any owners manual. Anyone have a similar switch that could provide some insight? Anyone want to take a wild guess? My first thought was that it would allow me to heat domestic water via my coach engine.....alas it does not. Coach is a 1992 Affinity.

[phays]

If you have the manuals for this coach look for the wire number lists and you should be able to determine where the wire with the number to the one connected to the switch goes or comes from. If you don't have the manuals, post the wire numbers here and maybe someone with your vintage coach can help.

The wire number looks like 134. On my 2000 Magna, wire 134 runs to the heat circulating pumps. On my coach, that would be the two auxiliary pumps that move engine coolant from the engine to the front dash heater core. One of the pumps on my coach is just above and in front of the engine and is accessed by raising the bed. The other pump is up front someplace.

If your wire numbers are the same as mine then it appears a previous owner installed the switch to shut these pumps down.

[smlranger]

Does your engine have an electric block heater? If not, is this perhaps the switch that activates a pump in your Hydro Hot/Aqua Hot to do engine pre heat? My Aqua Hot has an engine pre heat switch inside the coach.

[deandec]

As Phays indicates you probably have two "school bus pumps" that pump coolant from the engine to the dash heater and then on to the water heater (if you have no aqua hot) and back to the radiator.

The pumps cost about $200 each. The one at my engine area failed twice, so I removed it from the coolant line. The one behind the front "bumper" on the passenger side on my rig still runs continuously with the ignition.

That pump gives me over the road heating of the water in the water heater tank.

I suspect a previous owner installed your toggle switch to stop the rear pump from sending as much hot coolant to the heat in warm environments.

[Ron Burgundy]

Yes, I think you guys are on to something! My manual identifies wire #134 as "to cab heat circulating pump."

Will be taking the coach on a trip tomorrow and will do some experimenting. Can I assume that if I have been getting heat at the dash, my pump (or pumps) are functioning?

[deandec]

My manual says the same thing for wire 134.

If you have two pumps, you should have hot water upon arrival at destination without running the propane water heater.

Without the rear pump, we still get heat from the dash heater. So assuming may not be correct.

[Ron Burgundy]

Hmmm.... I don't think I have the capability to heat water via my engine. Will have to look into. I certainly don't recall reading about in my manuals.
provided I'm correct, should only have one pump (for dash heat). Sure would be nice if I did have the capability to hear water over the road.

[Peralko]

Ron,
Take a look at your water heater. If you have motoraid like we have, you should be able to see the water lines going into the water heater jacket.

[bneukam]

Dean,
Just purchased a 02 Intrigue, on the way home that same pump back by the engine started leaking antifreeze. Had a repair shop remove the pump and add a bypass in its place. Would you not recommend replacing it with new? Have you noticed a drop in your dash heat? By not replacing would it put more pressure on the other two pumps?

[deandec]

bneukam

We have noticed a drop off in the quality of dash heat, but travel primarily in AC conditions so it is not an issue for us.

If you have three pumps, then your system is different from ours. We only have two.

Our second pump is behind the passenger side front bumper, still works, and we still get water heated in our Atwood water heater by the hot coolant when traveling between destinations.

Our bypass has been installed since 2005 or about 50,000 miles ago. No problems that we are aware of.

Our system also had a shut off valve between the engine compartment pump and the dash heater. It was designed to stop hot coolant from going to the dash heater in AC type weather, I think. Our valve is now removed but I would have thought that both pumps would burn out if that valve had ever been closed.

Our pump(s) start with the ignition switch.

[bneukam]

Dean,
Thanks for the info.
I do have a total of three pumps, sounds as if mine are in the same location with a third one installed in the storage bay right next to the heater. I think I will stick with the bypass for now, and just see how she goes with out it.