Webasto heater blows cold air and air horn not work 09 prostar

Depending on how many hours is on the heater, you might want to consider some or all of the following: The fuel line has a screen/filter in it, which should be replaced if it has not been for a year or 2, the glow plug and screen inside of the unit itself can get crudded up and will limit the output, last and most expensive the firebox itself will wear out. My firebox lasted 7 winters, dealer said they have replaced them as short as 3 years. Lots of smoke on start up is usually a sign of glow plug, internal screen, or firebox problems.

 

ok, you have to count the flashes on that green triangle. it will flash 5 times quickly then give you the fault code in long flashes. count the long flashes and post here.

 

You will probably find your Webasto is flashing 5 times, then 1. The quick 5 flashes is not the code, just a space in between. If it is flashing code 1, this is very common. It means no combustion detected. Very common for these to have burners that are all gunked up inside and eventually will not fire. Most effective repair is to replace complete burner unit which comes as a kit.
Your horn is actually rather complicated. The air horn button on the steering wheel sends a signal to the body controller. The body controller sends 12volts to an air solenoid which allows air to the air horn. The solenoid is located on the left frame rail near the transmission. The horn is located under the front bumper area on the drivers side.

 

Try popping the air line out of the horn itself. It is just a quick connect fitting. At the end of the fitting where the line goes in, you will see a little collar. This collar is what locks the air line into the fitting. If you press the collar into the fitting while pulling out on the line, the line should come out of the fitting. Then press your horn button and see if you can hear air hissing from the open air line. The reed valve, or whatever it is, in the horn may be broken or plugged. If no air, I would say the air solenoid is buggered on the frame rail. The air horn solenoid will be mounted in series with other solenoids such as, 5th wheel slide, air suspension dump and possibly power divider lock. If those devices work, your air supply to the manifold is ok.

 

http://www.kamtrucking.com/resources/Webasto-Flash-Codes.pdf

This saves me from going out in the cold to get my webasto manual and scanning and posting it