TheSamba.com :: View topic - BN2 Gas heater troubleshooting in 73’ Fastback

Tue Oct 16, 2012 8:42 am

Hi

As I live in Norway and the winter is approaching, it would be comfortable to get my gas heater working.

I have been searching to get an understanding of the functionality, but I have yet not found any wiring diagram that is exactly correct for my model.

The main problem is that the gas-pump doesn’t work when the heater is turned on.

- The gas-pump works perfectly when I operate it manually directly on the battery.
- All fuses are intact.
- “Time relay” is reset.
- The glow-plug works.
- The fan works.

I have checked the voltage to the pump with a digital multimeter. The reading is alternating from 0-6 V, though it should be 0-12V. The problem is that I don’t know if the multimeter has high enough refresh rate to pick up the peak, so the problem could be ether to low voltage or too low current.

I have also noted that it won’t turn off automatically after a certain time without ignition (like I have read it should). It will keep going until I press in the knob. The heater looks almost unused (though not with the camera-flash in the garage) and otherwise in complete condition.

Does anyone have any experience of what can cause these symptoms?

Thanks for any help!

Regards, Kim

Wed Oct 17, 2012 7:19 am

Jason (aka Notchboy) probably has a ton of info. But these 2 links are about as close as I can get for help.
http://classicvw.org/gallery2/v/Fresh+Air+Heating/Eberspacher+Bulletins/
http://classicvw.org/gallery2/v/BN4_repair/

Also, if you go back a page on the first link, it gives instructions for installing the heater unit. I hope this helps.

Wed Oct 17, 2012 6:52 pm

Bus daddy is the man at this. I need time to look it up. Ive given him the information, hope he chimes in.

Sounds like a micro switch malfunction, or the quartz rod not being set right?

Wed Oct 17, 2012 7:13 pm

Could be, I'd check the thermostat at the output end for continuity first (small silver disc). The pump voltage sounds odd as well, the pump gets a constant 12 volts and the points in the blower (combustion end) regulate and pulse the ground to the pump, if you are reading an intermittant voltage on the green wire there may be issues with the relay or flame switch as already mentioned. Grounds are another big issue with these, not only the brown wire leading to the body but the connections inside and out of the case, the glow resistors inside the shell (follow the yellow wires) can be an issue if they are loose or corroded.

Clean tight terminals are the first thing to do when resurrecting any Eberspacher heater.

Tue Oct 23, 2012 6:50 am

Thanks for your help! :)

I have had some problems with the wiring diagrams since none of them matches my wiring colors.

At last I found this simple functioning diagram that I found helpful:

http://drbuzz.tripod.com/BN2pics/bn2.gif
http://www.speedyjim.net/htm/bn2.htm

Then, back to my readings:

- The thermostat has continuity, both "in place" and dismounted.
- The relay switches when the heater is turned on (it works).
- The green wire has 12v continually when the heater is turned on. (12.*v when the engine is on, 10v when off).
- The same has the green/white from the pump.
- Thermo switch operates properly, at least in "cold" position.

I did try to shortcut the green/white wire to earth in pulses while the heater was turned on, and the fuel pump worked.

From my perspective, from this point it looks like it is only the trigger in the fan motor that is the problem. How is it to open the heater? Is it easy to dismantle the fan, or do one have to take it all apart?

Sorry if my technical language is inaccurate or unclear, English is my second language ;)

Regards

Kim

Tue Oct 23, 2012 8:47 am

Maybe this will help, found it when collecting data on Type 3's.

http://vintagebus.com/parts/ebersp.html

Tue Oct 23, 2012 4:49 pm

KimSan wrote: From my perspective, from this point it looks like it is only the trigger in the fan motor that is the problem. How is it to open the heater? Is it easy to dismantle the fan, or do one have to take it all apart?
Here's a thread on your heater's bigger brother, pump contact cleaning and getting to the points is discussed a few pages in (same procedure for BN-2) : http://www.thesamba.com/vw/forum/viewtopic.php?t=343313

Wed Oct 24, 2012 8:10 am

Both was very helpful, thanks!

I just took it out of the car and started dismantling it. It went well until the flame switch -it was stuck, very stuck...

I have applied solvent with no luck. I'll give it some time, but I'm afraid it wont be a happy ending.

EDIT:

Aaand it is off :)
This heater is seriously clean, its just no dust or dirt inside and no paint degradation at all , don't look like its used much, probably been dead a long time.

Thu Oct 25, 2012 2:58 am

The rest of it went well, and I got finish rebuilding it yesterday.

I have not decided if it was a good timing or not, but today I woke up to snowfall. I am glad I put on car cover yesterday.

Anyway, the heater worked perfectly.

One question though, which size should it be on the fuel line? I only got 4 mm in my local store, but I guess that is a little big. It takes too long before the gas reaches the heater when turned on.

Thank you so much for your help, without you I guess it would have been a cold winter again. Really appreciate it! :wink:

Fri Nov 02, 2012 2:54 pm

KimSan wrote: One question though, which size should it be on the fuel line? I only got 4 mm in my local store, but I guess that is a little big. It takes too long before the gas reaches the heater when turned on.

The right size is inner diameter 1.5 mm, outside diameter 4 mm.

Actually, this is not unimportant. I used a inner diameter 4 mm hose after my overhaul, and the BN2 didn't work. Frustrated, until I was made aware that I needed the right type of hose.

Makes sense, since this is a low volume pump and it will use the heat-up time to fill up the hose. No gas enters the burner in time for the burner to start firing.

See you live in Norway - I ordered my hose from this store:

http://www.termomarin.no/aspx/produkt/prdinfovnet.aspx?plid=7808

Tue Jan 22, 2013 2:03 am

Boble wrote: KimSan wrote: One question though, which size should it be on the fuel line? I only got 4 mm in my local store, but I guess that is a little big. It takes too long before the gas reaches the heater when turned on.

The right size is inner diameter 1.5 mm, outside diameter 4 mm.

Actually, this is not unimportant. I used a inner diameter 4 mm hose after my overhaul, and the BN2 didn't work. Frustrated, until I was made aware that I needed the right type of hose.

Makes sense, since this is a low volume pump and it will use the heat-up time to fill up the hose. No gas enters the burner in time for the burner to start firing.

See you live in Norway - I ordered my hose from this store:

http://www.termomarin.no/aspx/produkt/prdinfovnet.aspx?plid=7808

Thanks, that was of great help! Both cheap and fast delivery. It took a while, but I finally got it installed. Now the fuel injects instantly. :)

I have a strange phenomenon. The glowplug glows, and it gets fuel, but 50% of the times it wont ignite. If I am lucky it ignites after 2-4 minutes. Yes, I do have the engine running while starting the heater. I tested the glowplug both with and without the engine, and its far faster with the engine running.

Fri Feb 01, 2013 4:12 am

With no other clue, I just ordered and installed a new BERU glow plug from ebay.

Now it ignites after 45 seconds, and work perfectly :)

Thanks all for our help!