12-21-2017, 09:05 AM
The compartment heat switch turns the fans on/off on the heater core in the water compartment in both my 77 and 93 coaches.
If there are return water hoses connected to the engine block without valves on them there will be no way to isolate a leak in the coach and water heater systems. Since the return hoses are always pressurized when the engine is hot, even with the supply side valves closed the leak will continue. If that is the arrangement it is not original from the the factory.
On the 77 coach I added a booster pump mounted on the driver side frame rail below the secondary fuel filter and powered it via a switch on the dash, the 93 coach has the same pump but it is triggered by a micro-switch on the dash temperature control slide lever.
On the 77 coach the water flow from out through the lower valve on the engine (this memory is several years old so it could be mistaken), through the boost pump, through the under-bad core, through the slide lever control valve, through the front heater core, to the compartment heater core, through the water heater, and then returns through the upper valve on the rear of the engine.
On the 93 the arrangement is lower valve, booster pump, control valve, heater core, compartment heat (I think) and return valve on engine. AND second lower valve on engine, under-bed heater core, water heater, second upper return valve on engine.
Since designs evolve from year to year I don't know how the above applies to any specific coach. I suspect an 84 coach with 2 valves would be more like the 77 coach, but if someone altered the setup it could anything. However the upper valve location is downstream of the thermostats and will be low pressure so I doubt it is possible to run a supply to anything from the location and return it to the block as the block pressure would be higher. If the lower valve is a supply and the return is to the block the only pressure difference would be due to the boost pump, probably inadequate to produce much heat up front.
If there are return water hoses connected to the engine block without valves on them there will be no way to isolate a leak in the coach and water heater systems. Since the return hoses are always pressurized when the engine is hot, even with the supply side valves closed the leak will continue. If that is the arrangement it is not original from the the factory.
On the 77 coach I added a booster pump mounted on the driver side frame rail below the secondary fuel filter and powered it via a switch on the dash, the 93 coach has the same pump but it is triggered by a micro-switch on the dash temperature control slide lever.
On the 77 coach the water flow from out through the lower valve on the engine (this memory is several years old so it could be mistaken), through the boost pump, through the under-bad core, through the slide lever control valve, through the front heater core, to the compartment heater core, through the water heater, and then returns through the upper valve on the rear of the engine.
On the 93 the arrangement is lower valve, booster pump, control valve, heater core, compartment heat (I think) and return valve on engine. AND second lower valve on engine, under-bed heater core, water heater, second upper return valve on engine.
Since designs evolve from year to year I don't know how the above applies to any specific coach. I suspect an 84 coach with 2 valves would be more like the 77 coach, but if someone altered the setup it could anything. However the upper valve location is downstream of the thermostats and will be low pressure so I doubt it is possible to run a supply to anything from the location and return it to the block as the block pressure would be higher. If the lower valve is a supply and the return is to the block the only pressure difference would be due to the boost pump, probably inadequate to produce much heat up front.
Jon Kabbe
1993 coach 337 with Civic towed