Webasto Valves

[jimshoen]

Finally took the time to figure out how my Webasto system works. This coach has three switches that cause the Webasto to fire off.

1) On the Marathon dash there is a switch call 'System Heat'. When this switch is pushed the Webasto fires and the small pump inside the Webasto circulates hot water through the two 10 gallon water heaters and now we have hot water.

2) There is a switch in the main electrical panel in the rear (bedroom) that says '12 Volt Water Heater'. Push that switch and the exact same thing happens as in #1. Interesting?

3) There is another switch in the main electrical panel in the rear (bedroom) that says '12 Volt Heat'. When this switch is pushed the Webasto fires and the small pump inside the Webasto circulates hot water through the two 10 gallon water heaters. Also, if any of the three heat exchangers in the coach that use the hot water for heat are calling for heat a solenoid valve opens and another aux pump in the spare tire area turns on which circulates hot water through all three of the interior heat exchangers. Now we can heat the inside of the coach. Nice!

That left me with only one more thing to figure out, how does the Webasto pre heat the engine. Well, after hunting all around I finally determined that in this coach the Webasto does NOT pre heat the engine. The Webasto system picks up and delivers coolant to the line that connects the coolant surge tank to the water pump (engine). By pure coincidence some of the heated coolant makes it down to the Water pump and warms it up. This was real informative beacause for the last year I believed the Webasto pre heated the engine.

All is not lost as the coach is equiped with a 120 volt block heater which works good. Mystery solved.

Below are a couple pictures of the three valves located at the Webasto unit. I'd like to confirm that these are just solenoid valves and not pumps?

[gmcbuffalo]

Ji
my vote is solenoid valves.
GregM

[Joe Cannarozzi]

I would be very suprised if that was not set up to preheat the engine.

[truk4u]

Jim,

I think you'll find the engine pre-heat to be in the loop. On my 97, when the 12 heat was selected (heat exchangers), it also circulated coolant through the engine.

You also should have a breaker in the 120v panel in the bedroom marked Block Heater. On mine, that breaker controlled the electrical box in the engine compartment that the block heater is plugged into. With the block heater unplugged, it made a great place to plug in a 3 stage charger for the chassis batteries and if the bus was going to set for a month or two, I would just through the breaker and keep the batteries topped off.

[Jon Wehrenberg]

No need to guess. Fire it off and after a few minutes feel around the engine, probably the water pump area is best. You will know if the engine is in the loop.

[jimshoen]

Joe. I am surprised too. I always thought Webasto equals engine pre heat?

Jim and Jon. Ran the system and the engine does not get warm. Can not find any plumbing that would allow Webasto heated coolant to circulate through the engine.

Jim. Yes there is an electrical outlet (GFI Duplex) connected to the 'Block Heater' circuit breaker in the engine compartment and it works now that I replaced the GFI duplex. The electric block heater that plugs into it works well and does pre heat the block when turned on and plugged in. I do have a 24 volt battery maintainer that I plug in there when the coach is stored and it keeps the chassis batteries up.

Jon. Of the three valves located with the Webasto, two have a round body (see the top right and bottom right pictures) and one has a square body (see the bottom left picture). Could the two round bodied units also be circulation pumps?

[Ray Davis]

1) On the Marathon dash there is a switch call 'System Heat'. When this switch is pushed the Webasto fires and the small pump inside the Webasto circulates hot water through the two 10 gallon water heaters and now we have hot water.

2) There is a switch in the main electrical panel in the rear (bedroom) that says '12 Volt Water Heater'. Push that switch and the exact same thing happens as in #1. Interesting?

Where is the "System Heat" switch. I don't recall seeing that on my Marathon. I do have the 12 Water Heater, which does exactly as you describe, but if there's anothe switch, I'd be at least interested to know.

Ray

[Jon Wehrenberg]

Jim,

They all look like solenoid operated diaphragm valves.

I have pushed for this before, and maybe if we as a group can get some critical mass we can do converter specific seminars.

I diagrammed my Webasto system, but the fact that it is a Liberty and virtually all Libertys have OTR air makes the learning of my system of no value to any but other Liberty owners.

Each type of conversion needs somebody to volunteer as the guru who learns the systems and teaches about them.

[jack14r]

Call Leon at Marathon,he will verify how the system works.

[gmcbuffalo]

Jim could one of the solenoid not be working and allowing heat water reaching the engine. Have someone turn the system on while you feel of movement in the solenoid. Or are they getting current? or jump voltage to it and see if they work.
Greg