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02-17-2010, 11:57

Taken with a grain of salt.... since my coach was a little newer and may have been slightly different.

Engine heating for cold weather starting consists of two systems:

1. engine block heater -- usually operated by a red lighted 120 VAC type switch located in the galley area on newer coaches. (Older FC models had these somewhere around the driver's position.) This is a standard 120 VAC electric block heater that provides about 1000 watts of electric heat to the engine block. It is moderately effective and requires many hours of operation before it does much good.

2. Engine preheat. On the hydronic heat models, this turns on a pump that runs the hydronic heat through the engine coolant to warm the engine. This is usually effective in warming the engine for a cold weather start in 30 minutes to a couple of hours depending on ambient temperature. (Switching my engine preheat on at 6 AM for a planned 8 AM departure in freezing weather (in the teens) would let the engine start up as if it were a 70 degree day.)

The engine preheat switch should be "ON" _and_ the hydronic heat system must also be on. On the 43' WBDA model, that required the switch over the driver to be on and the hydronic heat switch on the dashboard to be on (showing a green light) at the same time. You should also hear the hydronic heat system burner go on. When the system is operating, the water temperature gauge may begin to come up off the pin after about 30 minutes and show 100-125 degrees after an hour or two. (At least, my water temp gauge would do this -- but when the engine would start, the temp gauge would drop back to not showing anything as all the water in the radiator mixed in with the water in the block.)

To make matters less helpful, my switch moved up and down -- and was marked on and off.... <sigh> so I can't really tell you which way is which. However, if you turn on the hydronic heat, let it reach temperature until the burner switches off -- then flip the engine preheat switch, you should get the burner to come back on.... or you can go around to where your heating system is and listen carefully while someone turns the switch one way or the other to see if you hear a pump come on.

Perhaps someone with a 91 will respond.

Pete Masterson

(former) '95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA

"aeonix1@mac.com"

On Feb 17, 2010, at 3:32 PM, mbulriss wrote:

OK, I have one of those how-to questions that is not answered in 'the book'. On my 91 on the far left topmost driver overhead dash panel, there is a black two position toggle switch labeled "Engine Preheat" - that's it, no "on" or "off" indication, no light. My question is: Is "on" when the switch is toggled in to the left side or the right side of the switch? What kind of electrical draw should I see on any of the gauges when it is on - *if* it is working?

Normally, we try to stay out of such climates where I would actually need said switch, until this past weekend in the Texas hills where it got well below freezing. ;^)

Thanks,

Mike Bulriss
1991 WB40 "Texas Minivan"
San Antonio, TX

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