Webasto Air Top Evo 3900 Lesson

Salmon Fisher

Active member
Joined
May 28, 2019
Messages
34
Fluid Motion Model
C-28
Vessel Name
Kim Christine
We own a 2015 Ranger 27 with the Webasto Air Top Evo 3900 diesel heater.

It stopped working on a recent trip to the San Juans in May. Would not start and had white smoke coming out. Called Sure Marine in Seattle and they said it was probably carboned up. I wondered how to take it out and found how to right here:
viewtopic.php?f=6&t=9302&p=64346&hilit=webasto+service&sid=4d44e8ff71259572b49fa6d5e932e93c#p64346

One of the most important parts of removing the heater was from the Technician at Sure Marine. He told me how to access the wiring harness on top of the heater. Basically, pop off the white cover where the harness goes in then unplug both harnesses when the heater is unbolted from the bracket. All of this was done in a variety of body positions. I had to remove the port v berth cushion and bolster, unscrew and remove rear v berth wall panel and there it was; the heater.

Removed and taken to Sure Marine in Seattle. They got it fixed and I reinstalled this morning. It runs like a champ!

The lesson from the Technician:

Always start the heater on "High" and then you can adjust it for comfort. When getting ready to turn it off,turn up the thermostat to "High" and let it run for at least 5-7 minutes and then turn it off.This lets the heater burn any moisture, soot or carbon out before it starts to build up.
The Tech said the heater had about 500 hours on it, recorded by the unit's ECU. I was advised that a new burner should be installed, so that was completed, too.
Just remember, "Start heater on "High" and turn heater back up to "High" for 5-7 minutes before shutting down. This should save someone a few hundred dollars.
 
Wise advice and thanks. I should probably have mine serviced this summer. I don't have any idea how to get at it in a C30 CB. I know it's somewhere under the range or sink...
 
If you roll back through some earlier threads this sage advice appears multiple times: run your Webasto on high whenever you can stand it.

Also, the controller is very finicky if there has been any kind of a voltage drop, requiring multiple pulling and reinstalling of fuses before it comes back to life. Again, that appears in lots of posts to this website.

I hope when Ranger/Cutwater finally gets around to modernizing this site (been promising this for years) that questions like this will be easily retrievable.

Jeff
 
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