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Old 11-01-2011
Jim Magowan Jim Magowan is offline
Senior Member
Join Date: Jan 2008
Location: Anchorage
Posts: 114

We put a lot more hours on both the generator and the webasto than on the engine. The Webasto (Scholastic) is installed in what we call the water bay, where the HWH, water pump and water pressure tank are (originally there was a propane grill that was stored in the bay, where we put the Webasto).

We do a considerable amount of winter camping (our coldest camp out was at Destruction Bay by Kluane Lake on the way to the Haines Eagle Festival when the air lines froze and we were stuck for a day and a half at -30f.) and even in summer we often have cool weather (and at least one of the propane heaters always seems to be out) so the Webasto is critical to us for cabin heat, hot water and engine starting.

We carry a spare nozzle for the Webasto and it is a good idea to change the nozzle annually. All it takes to change the nozzle is a 10 mm open end wrench to open the housing and a 16 mm open end (depending on the installation a stubby 16 mm might be helpful). If you know what you are doing it can probably be done in 15 or 20 minutes.

After the bus was in the shop to have the fan clutch sensor replaced the Webasto wouldn't fire. There is a small black cover on top of the unit that covers three sensors. The sensors can be changed in five minutes or less if they go bad. AS I found out, checking them is easy if you know what you are doing (I There are three sets of wires for the three sensors, a red and a white wire to the one that shuts of the heater when the coolant reaches 175f, two greens to the second temp sensor and two white to a wax pellet sensor that opens (the wax melts) if the chamber overheats (such as when there is too much air in the cooling system). All you do to check the sensors is use an ohm meter to test for continuity. As I found out the hard way, set the meter on the minimum (200K on my meter) and the reading will be around .1. After I tried for over a week to get the thing working it took Dewey, the local Webasto Master about 2 minutes to find the problem and get it working.

The hot chamber sensor rarely foes out because the chamber doesn't get that hot except when the guys at the shop did not get enough air out when they tried to bleed the cooling system after replacing the fan sensor (they removed a radiator hose to get to the sensor).

After almost nine years it looks like we have solved the problem with the hydronic hearting system. We have never been able to get heat from it when we are driving. When the engine was off we got good heat using the Webasto.

We found that the take off hoses for the hot water heater heat exchanger were installed after the circulating pump for the heater instead of before the circulating pump as the factory diagram shows. (It is not uncommon for the assembly line guys to know "better" than the engineers. In any case the problem was compounded because the Webasto was fed directly from the engine and the coolant from the Webasto went into the system where the take off for the HWH was. The circulating pump is a low pressure pump so when the engine was running the coolant has a 'short circuit' thru the HWH heat exchanger and back to the engine without going through the heater cores.

I had the hoses changed so the HWH heat exchanger takes water before the circ. pump and the Webasto puts heated coolant into the system after the circ. pump. We are now getting heat when the engine runs as well as when just the Webasto is running. There still seems to be air in the system so the heat is not as much as I hope it will be when I get the system purged of air (a very difficult job with this coach).
Jim Magowan
90 36 SP
Anchorage AK
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