TheSamba.com :: View topic - BN-2 Eberspacher Gas Heater help!

Wed Nov 19, 2008 5:45 pm

Need some info and advice where I've not used one of these gas heaters before. This seems to be "the" forum for knowledge on these units. I'm installing it in a non VW, so I just need a few questions answered and one wire explained:

I have a BN-2 gas heater that I bought used w/o the wiring harness from the heater to the car, but have one wiring question: I have a light grey wire coming off the plastic (resettable ) safety switch which seems to lead off the gas heater and has a multiple male electrical connector attached that has an insulated clear plastic recepticle over it for attaching two other wires, but have no idea where it connects. I suspect that it's supposed to go to a switched ( on-off ) 12 volt power source and once connected would feed safety switch and then thru that to the glow plug and fuel pump, but can't tell as I don't have the original switch or the related wiring.
So where does the light grey wire go?

Second question: the BN-2 I have has a Hardi fuel pump and fuel regulator ( no fuel return line to the gas tank ). I've seen some smaller metering pumps advertised, but they appear to have a fuel line that goes DIRECT from the metering pump to the jet holder next to the glow plug... and no fuel regulator like on my BN-2 with the bigger Hardi diaphram pump that uses the fuel regulator. Are these fuel systems interchangeable? Can I use the metered Espar small pump and not use my fuel regulator and Hardi pump? Is the Espar metering fuel pump a self contained pump + fuel regulator?

I've disassembled, cleaned, and checked everything on the BN-2, but can't figuire out that light grey wire. As it sits with the grey wire unattached, I can't get power to the fuel pump or glow plug, and pushing the red re-set on the safety switch obviously does nothing--so I'm thinking the grey wire is for switched power input, but want some advice before I try that.
Thxs
Doug

Thu Nov 20, 2008 2:09 am

There are wiring diagrams and repair manuals on line.

The gray wire goes to the dash switch. The brown is ground and the fat red is a fused, always hot lead.

The fuel pumps are not interchangeable as the one without the regulator is a pulse type pump powered from a set of points in the combustion fan. It is a later model that allows adjustment of the output temp via a screw next to the little fuse. Your model does not have this adjustment.

This should help>

http://classicvw.org/eberspacher/install/

jim

Fri Nov 21, 2008 5:09 am

I have a late BN-2 with the metering pump, temperature regulating switch, etc. The manual only tells about its existence, but: where is the fuel (metering) pump supposed to be located (under the tank or close to the heater)? It also has a gas "draining pipe" (no.13 in the picture below) with a hose on it, where is this supposed to go?
Thanks.

Fri Nov 21, 2008 5:17 am

That type of pump should be down low below the tank. It won't lift gas up.

That model has a return line that was originally fitted with the feed line on to the top of the tank.

Here is a pic of that type that shows the fuel pick up. It's for sale at a wrecker here. Has a different pump though. That is not a metering pump but has a regulator instead.

There is another recent thread on gas heaters that goes into alternative connections for this type. I thought creating fittings in the gas sender was the safest easiest and closest to stock.

jim

Fri Nov 21, 2008 5:51 am

I see. Thanks. I saw the other thread, but i thought the return line on a B2 or early BN2 is a different case from this one. I also managed to start the thing and, even when the glow plug wont't work, you only get a few drops of gas from that drain. Does it really need to be returned to the tank (for environmental reasons)?
Anyway, a fitting in the sender seems like good idea, but won't fuel vapour from the tank exit into the heater?

Fri Nov 21, 2008 3:02 pm

This is an earlier one. The later ones had the metering pumps and adjustable heat.

The return line was designed to go in the top of the tank so that's where I would put it. The models without the return line have a pressure regulator.

Do you need a glow plug? Some parts are available here.>

http://www.germansupply.com/home/customer/home.php?cat=376

I also have many hard to get parts like brackets and ducts.

jim

Fri Nov 21, 2008 4:17 pm

BN-2 heaters do NOT have a return line.
All this babble about B2 heaters only confuses people. Keep the information in a separate topic.

Fri Nov 21, 2008 5:44 pm

Bruce wrote: BN-2 heaters do NOT have a return line.
All this babble about B2 heaters only confuses people. Keep the information in a separate topic.

Isn't the one above a BN2? I thought it was.

The post above said>

"I have a late BN-2 with the metering pump, temperature regulating switch, etc. The manual only tells about its existence, but: where is the fuel (metering) pump supposed to be located (under the tank or close to the heater)? It also has a gas "draining pipe" (no.13 in the picture below) with a hose on it, where is this supposed to go?

jim

Fri Nov 21, 2008 7:48 pm

James, the one in the pic you posted is a B2, not a BN-2.

Fri Nov 21, 2008 7:53 pm

jan72 wrote: I have a late BN-2 with the metering pump, temperature regulating switch, etc. The manual only tells about its existence, but: where is the fuel (metering) pump supposed to be located (under the tank or close to the heater)? It also has a gas "draining pipe" (no.13 in the picture below) with a hose on it, where is this supposed to go?

There are 2 types of BN-2 heater bodies. The heater in your diagram is the early type with a fuel pump and a separate pressure regulator. The pump and reg are mounted directly onto the heater body.
The late type BN-2 has a metering pump that is separate from the heater, and mounted under the car, opposite of where the master cylinder is.

I'm pretty sure item #13 is not for draining fuel. Maybe for condensation due to combustion.

Sat Nov 22, 2008 1:53 am

Good to know Bruce. Thanks. I finally have these things all figured out, even that double relay, so now I need to keep my models straight or it will get confusing.

There are several incarnations of the BN2 as you said but do none of them have the return line? Do only B2's have the return line?

I've had many VW's since my first '65 in '69 and they all had gas heaters but I never worked on them back then or even noted the model number as they were very reliable and never quit on me. Now however I have 3 VW's with them and all have needed some work. That's why I have 3 spares as well.

It's amazing how well these things have stood the test of time though. I just fixed one from a wrecker that had a bad relay. Took it apart and it was rusted badly. The little springs were rusted solid. I brushed and sprayed in it and filed the points and it's in my car now running like a champ.

The electrics are a b*tch to understand but I finally got it figured out so I'm working on a description of the operation that includes wire colors and terminal numbers and how that damn relay works. I've got to do it soon before I forget. LOL

jim

Sat Nov 22, 2008 2:22 am

jamesdagg wrote:
There are several incarnations of the BN2 as you said but do none of them have the return line? Do only B2's have the return line?

I had a look at a few of the BN-2 heaters in my garage last night. Two very early Type 3 BN-2 heaters did have a small rubber drain hose between the combustion air intake and the exhaust. The BN-2 heater that originally came in my 72 Super (with pump and regulator on the heater) did not have the drain. A plastic plug covered up the hole.

Refer back to the diagram above. This drain is nowhere near where fuel is delivered to the combustion chamber.

Sun Nov 23, 2008 12:16 pm

Well, i didn't take pictures, but i will. I think the unit i have is a late BN-2, it has no pressure regulator and there's not enough space to put one, it has a metering pump that's moved by the "points" or whatever it has on the fan, it has a thermostatic control switch, like you said (one can adjust temperature from a little screw - secured with a drop of green paint - located under the 8A fuse)...
Still, it has what's called on the diagram (sorry about it's dimensions, i shouldn't upload it on imageshack, but on samba gallery) a "drain pipe". It is located, like you said (on early BN-2's, though), between the exhaust and the combustion air intake.
I tried to start the heater, but the battery was weak. The glow plug didn't reach its working temperature, i think, and the heater didn't start. Meanwhile, the pump gave it gas, some of which made it through down that drain pipe. After charging the battery, it did start and worked until the temp. switch killed the pump. Unfortunately, i wasn't able to start it again, because of the battery, of course (no more loading capacity and dies quickly and could't energize the pump).
Do you think this may be a combination obtained from both late and early heaters? Remeber, no regulator, but drain pipe hole on the case. I think these are the original case halves... The only non-stock thing was a second switch installed by someone to kill the fuel pump (i have to revise the wiring and the flame detecting/safety switch, maybe one of these wasn't working and the guy wanted to be sure).
I'm taking pictures tomorrow...

Sun Nov 23, 2008 6:46 pm

Mine will not start unless the engine is running. Then after 40 sec's when the glow plug cuts out I can shut off the engine and run it for a long time. It floods if I try without starting up.

The flame switch doesn't control the pump. It shuts off the glow plug when it detects flame and it keeps the fan running for the cool down time which is adjustable.

The pump stays powered (+) from the double relay until the main switch is shut off. It is interrupted momentarily by the temp sensor under the fuse, in your model. The ground to the pump is controlled by the fan contacts.

The glow plug is part of the resistance that drops the voltage to 4 V. If the surface on the heater where the glow plug seats is dirty the resistance goes up and the volts go down.

jim

Sat Nov 29, 2008 2:33 pm

Ummm. that screw with the dab of green paint under the fuse is the overheat safety switch adjusment, when the heater overheats it blows that fuse and kills everything. The fuel pump is controlled by the little silver disc in the outlet duct and isn't adjustable.

Anybody have a link to a late BN-2 manual showing the output measurement for the metering pump? The link James provided only covers the regulator style BN-2 and the only metering style shown is for a BN-4 which is a different amount AFAIK.

Thu Dec 11, 2008 6:47 pm

OK you gas heater guru's, a few questions on two different BN-2's ( early and late style ) 12v gas heaters:

Question #1: I have a late style BN-2 ( rotary metering pump ): I can't get fuel from the rotary pump up to the heater. The pump clicks, but sure doesn't seem to put much if any fuel out. How long does it take for that rotary pump to fill the line and let the heater actually ignite? The rotary pump doesn't seem to have much "suction" compared to the earlier BN-2 I have that had the much bigger Hardi fuel pump and separate fuel regulator. One of the earlier posts here said the rotary fuel pump needed to be mounted BELOW / under the gas tank ( gravity primed? ) for it to work? Does the fuel tube outlet near the glow plug have a jet in it? Or does it just get fuel pushed out to the glow plug by the rotary pump "metering" pressure ( why it's called a "metering" pump? ).
I have had the whole unit ( Heater + pump ) out of the car and apart but can't get it to ignite when I bench test it: the fuel pump just doesn't seem to be getting fuel to the heater? How long should I let the fuel pump click away? I've run it long enough to have to reset the safety switch rest a few times to let the fuel pump keep clicking, but still no fueled ignition, and I've tested the glow plug and it's fine / plenty hot. Advice?

Question #2: Someone mentioned that the LATE style BN-2 ( with the rotary fuel pump ) has a thermostatic adjustment to turn up/down the heat output? Where is that located? How does it "adjust" the heat output?

Question #3 ( for my older BN-2 that has the big Hardi brand diaphram fuel pump ): I can get the heater to ignite, but it's running VERY smoky out the exhaust pipe...like it's way too rich, but I don't see any adjustment other than the screw & locknut on the pressure regulator on the top of the heater unit. That screw doesn't seem to do anything to adjust / change the rich mixture not matter how much I turn it. It smokes and stinks so much I can't use it. And when it's running, it doesn't really seem to be putting out that much heat.
Help!
Doug

Thu Dec 11, 2008 7:34 pm

busdaddy wrote: Ummm. that screw with the dab of green paint under the fuse is the overheat safety switch adjusment, when the heater overheats it blows that fuse and kills everything. The fuel pump is controlled by the little silver disc in the outlet duct and isn't adjustable.

Anybody have a link to a late BN-2 manual showing the output measurement for the metering pump? The link James provided only covers the regulator style BN-2 and the only metering style shown is for a BN-4 which is a different amount AFAIK.

Your getting the models mixed up now. That screw near the fuse adjusts the temp on the metering pump models and you are right it simply blows the fuse on the regulator type.

I'll find the pump volume for you.

jim

Thu Dec 11, 2008 7:40 pm

Dougallen wrote: OK you gas heater guru's, a few questions on two different BN-2's ( early and late style ) 12v gas heaters:

Question #1: I have a late style BN-2 ( rotary metering pump ): I can't get fuel from the rotary pump up to the heater. The pump clicks, but sure doesn't seem to put much if any fuel out. How long does it take for that rotary pump to fill the line and let the heater actually ignite? The rotary pump doesn't seem to have much "suction" compared to the earlier BN-2 I have that had the much bigger Hardi fuel pump and separate fuel regulator. One of the earlier posts here said the rotary fuel pump needed to be mounted BELOW / under the gas tank ( gravity primed? ) for it to work? Does the fuel tube outlet near the glow plug have a jet in it? Or does it just get fuel pushed out to the glow plug by the rotary pump "metering" pressure ( why it's called a "metering" pump? ).
I have had the whole unit ( Heater + pump ) out of the car and apart but can't get it to ignite when I bench test it: the fuel pump just doesn't seem to be getting fuel to the heater? How long should I let the fuel pump click away? I've run it long enough to have to reset the safety switch rest a few times to let the fuel pump keep clicking, but still no fueled ignition, and I've tested the glow plug and it's fine / plenty hot. Advice?

Question #2: Someone mentioned that the LATE style BN-2 ( with the rotary fuel pump ) has a thermostatic adjustment to turn up/down the heat output? Where is that located? How does it "adjust" the heat output?

Question #3 ( for my older BN-2 that has the big Hardi brand diaphram fuel pump ): I can get the heater to ignite, but it's running VERY smoky out the exhaust pipe...like it's way too rich, but I don't see any adjustment other than the screw & locknut on the pressure regulator on the top of the heater unit. That screw doesn't seem to do anything to adjust / change the rich mixture not matter how much I turn it. It smokes and stinks so much I can't use it. And when it's running, it doesn't really seem to be putting out that much heat.
Help!
Doug

Bleed the pump by disconnecting the hose at the heater and running the pump till you get gas. It's a metering pump because it does not run all the time like the Hardi but only gets pulses of power from the fan points.

The metering pump ground wire runs through that small fuse and the screw next to it is used to adjust heat output by interrupting the ground momentarily.

The smoky unit probably needs the pump adjusted. I'll look up the volume as I said above.

jim

Thu Dec 11, 2008 7:51 pm

Late BN-2 with metering pump>

Pump should click 171 - 183 clicks per minute and deliver 6.25 - 6.55 cc per 200 clicks. Fan should turn 5,450 - 6,050 RPM

To adjust:

Remove fuel hose on delivery side and remove protective cover.
Loosen check nut while holding pump housing firmly.
Rotate valve guide 1/4 to 1/2 turn. Rotating counterclockwise increases the flow of fuel.
After setting seal check nut with paint.

jim

Thu Dec 11, 2008 8:01 pm

Hell while I've got the manual out>

Heat output = 2300 W
Electrical input = 40 Watts

Temp switch delayed blower shutoff time = 120 - 180 sec.
Safety switch response time = 130 - 170 sec
Regulating switch cutout temp = 130 - 160'C (266 - 320'F)
Safety thermal cutout switch temp = 180 - 200'C (356 - 392'F)
Blower speed = 5450 - 6050 rpm = 171 - 183 pump strokes per minute.
Fuel consumption = 0.32 to 0.36 l/hr 911.3 to 12.7 ozs/hr
Pump point gap = 0.4 mm (0.0157 in)

Manual also has instructions on adding a relay o use the heater as a ventilator.

jim