Thursday, May 10, 2012

How Do You Keep Warm in a VW Bus?

This morning was cold and rainy. Not a nice day. But in just a few minutes I was sitting up, eating breakfast and looking at Internet headlines, toasty warm still in my pajamas. The secret? An Eberspacher gas heater.

Only a few buses sold in the United States were originally fitted with these fine examples of German engineering. A lot of buses sold in Canada, however, were, so I am told.

They are marvels of caloric output.

They blow piping hot air through duct work beneath the rear seat into the passenger compartment.

It only takes a few minutes to take the chill out of the air, and only a few more to make things really toasty inside.

The picture above shows an Eberspacher BN4 similar to the one I have in my bus. Note the fan visible at the entrance. It pulls air into the heater,  past a small combustion chamber and dumps it into your interior at a temperature of about 120 degrees.

Below is the duct beneath my rear seat where tha air comes out.

The bus I have did not come with a heater.  I did a lot of looking and scrounging on eBay and Samba to find one, and to find the duct work needed to install it.

Finding a working, adjustable fuel pump is one of the hard parts.

Adjustment part is critical for your heater to work right. If too much gas is fed to the heater it will burn rich and emit black soot and foul smelling smoke, and will eventually foul yourspark plug/glow plug.

If too little gas is fed into the heater it will not run, or will run too hot and automatically shut down.

Installing a heater requires cutting through the firewall in the engine compartment.

When I installed my heater I made a modification that I recommend. I installed an inexpensive mechanical  thermostat behind the driver's seat and wired the heater to it. It should be mechanical. A mercury switch will not work accurately on uneven ground or when the bus is in motion.

The modification did away with the need to install a cable to lengthen or shorten the on/off cycles to control temperature.

And, like a house thermostat, it can keep your bus at a constant temperature. Or trigger your heater to come on at night when the temperature drops.


VW buses are notorious for being cold to ride in.

When the outside temperature falls below 40 the heat exchangers on an air-cooled engine cannot keep up with the cold air leaking in through the cracks and worn seals and jalousie windows.

So having a gasoline heater helps when driving. The duct at the base of the back seat blows warm air forward to the driver's compartment.

The heater does require electricity to run. A good house battery is a must. It also requires gas but not much. One or two pints will keep you warm through the night.

To the left is my heater.
The fan blades are not visible. They are shielded by a plastic cover that draws air from higher in the engine compartment.

Used Eberspacher heaters are still available but good ones are increasingly rare. If you do find one make sure it is in good operating condition.

There is no one any longer that I know who repairs them. They are complicated. And parts are hard to find.

But the upside is drinking coffee and eating toast, warm in your pajamas on a frosty morning in your Volkswagen bus.


  1. Hi, nice blog! I have a 71 Westy with a functioning gas heater can you explain the wiring hookup to the mechanical thermostat? seems like a smart idea.

    Thx Steve

    1. Hi Steve,

      Thank you for the kind words.

      I'm at a disadvantage here without knowing how your heater is currently wired. Basically, there are two wires that carry juice to your heater. One carries the juice for operations -- turning the fan, firing the fuel pump, heating the glow plug. The other is to turn the heater on and off. This just be connected to your on and off switch.

      By routing that wire to a thermostat connected to 12-volt power, you can then use your thermostat as your on and off switch.

      Another way to do it that may be easier and work for you since your are already wired in is simply to find the wire from your on/off switch going to your heater and route it through the thermostat. That way you can leave everything as it is but control the cycling on and off with a thermostat.

      I don't think I've done a very good response to your question but I'm sure if you play around with it some it will become clearer.

      All best wishes to another Bus driver!



      Basically, there are two input wires carrying 2 volts into your heater. One is main power source and should not be change. The other is to the

    2. Thanks John, understand your method perfectly, thanks for passing it along. Camping this weekend and the forecast is for a night time high of only 5C, so may be using the heater sooner than I thought. drive safe!

  2. Hi John, I guess I better check up on weather conditions in NM! to me that one would need a heater there on May?

  3. Hi John! I picked up one of these heaters that seems to be in good condition. I have been looking for a fuel pump though. What did you use?

    1. These fuel pumps are very hard to find in good working order. The one I originally good had was not very good. Asking around on line I was able to find some with a spare. Being able to adjust the measured flow is critical. Too rich and you will get black smoke which is not pleasant and also you will foul the spark plug, have to remove and clean it. Too lean and it won't fire up. I wish you the best in your search. While few U.S. buses come came equipped with these heaters, Canadian buses did, so there are some sometimes available from our northern cousins. I would start my search by going to Samba. If not familiar with the site you can search for it and find it on line. It is a great swap meet and resource for all things VW. Then search Eberspacher and see what comes up. You DO want the right one and in good condition. Best of best wishes, John

  4. It was great to see the old printshop and everyone who works there again. I am excited to see a printing business still operating and growing, great job guys
    1953 Chevy Pickup