Eberspacher Bn4 Thermostat

[BuckeyeBus]

I'm looking for an alternative to the Eberspacher Bn4 thermostat that seems to be more and more difficult to find. I have a Fenwell thermoswitch that will turn on and off at a preset temperatures
, but it is not adjustable once installed on the vehicle. Any ideas would be appreciated.

[mondshine]

At the risk of lots of ridicule, I will tell you how I did mine.

My car's BN4 thermostat came with a broken "barber pole" bi-metallic spring.

For the output duct, I fabricated an adapter for a simple adjustable snap disc limit switch.

Example:

It is connected electrically just like the original part. It prevents an overheat condition in the output duct.

Inside the car, in place of the cable, I installed a 100KΩ linear potentiometer to control a Velleman Mk 137 thermostat.
Example:

The potentiometer and thermistor (the blue blip) were removed from the board , and mounted remotely, so the board itself is enclosed in a tiny "project box" behind the dash.
The thermostat switches the gray wire from the heater.

All of this stuff cost less than $40. It is all reversible if I ever come across a good original part for a good price.

Meanwhile, with this setup, the thermostat is regulating the temperature inside the cabin, not inside the output duct.

Considering that I drive my Thing 99 44/100% of the time with the top down, none of this long story means very much!

Good luck, Mondshine


Edit:
I used a Velleman Mk 137 thermostat to regulate the BN2 heater in my 1971 Super which was my daily driver here in Michigan from 2008-2013.
Ordinarily, BN2's don't have any thermostatic control; they are either on or off.
In this photo, you can see the potentiometer and thermistor (the little blue blip) on the left side dash panel.

I miss that car.

[BuckeyeBus]

Yes Mondshine, my old thermostat literally fell apart during the repair of the Bn4. I appreciate your suggestions, and will work on it this week. Updates to follow. Thanks again.

[perello]

i use this type

which seems to be more robust? at least in europe its still available.
_________________
Aug '58 pressed bumper SO23
1974 German Thing
1978 Bug 1200

[BuckeyeBus]

Looks pretty nifty Perello. Looks like German Supply. Can that be installed on the BN4 Thing heater? Thanks for your help.

[mondshine]

Here's a line drawing from the BN4 manual. It's an early model heater, but you will get the idea.

You can see the stamped metal temperature regulator as it would be installed on the sheet metal ductwork common to Type 2's; notice the rectangular hole where it is fitted.

I have never seen a plastic "181 style" output duct set up with the the rectangular hole for the stamped metal regulator.

I cannot speak to the rarity/availability of the 181 output duct, but I would be reluctant to chop mine up unless I had another one in hand. That's not to imply that it can't be done; but I always prefer to make modifications that are reversible.

Good luck, Mondshine

[volkybus]

Good post on the gas heater. mine caught fire a couple of falls ago and although it worked fine for over 10 years .now It makes me nervous so it's in inop mode...Since I don't drive past Nov I just dress warmer..I would like to get it operating again so these tips are handy..I have. 8 or ten of them (gas heaters) but nobody works on them anymore..but I buy them for parts, just in case..I also have a Eberpacher in my 74 Bus.the fuel pump is broken so she sits ..My experience is w a 64 bus and the thing one...Last time I had a airplane mechanic fix it as they are common on light twin airplanes.
We fixed one on a small plane in Grand Junction Co a few years ago on a cross country trip..but it was only a couple of fuses.. Fun trip..Good luck Bill inPR

[perello]

[mondshine]

[perello]

now i realise that probably the plastic duct is different?
_________________
Aug '58 pressed bumper SO23
1974 German Thing
1978 Bug 1200

[BuckeyeBus]

I like how that is configured. I see German Supply does not have any in stock. Any idea where I can buy one??? Thanks.