"Help me!" cried the gas heater.

[scarroll]

I've got a BN-4 heater in my '73. I don't get any gas coming from the fuel pump when the heater's turned on, and I don't hear any of these clicking sounds that I've read about on other threads. What has me puzzled is that the two wires that go down to the pump are both "hot" (12volt, positive) when turned on. Shouldn't one of these wires be a ground that doesn't light up a test lamp?

[7thing3]

That doesn't sound right--trace them back up to the top. In the meantime take out the pump and hook up a couple of test leads to a battery. It should click each time you touch the positive to the battery. Don't hold it on there forever as it is only designed for an intermittent current flow. Without getting underneath Ted I think there is a brown wire that should be the "-" and another color (Black?) that is the "+". You could always run a jumper from the negative side of the pump to the frame just to see if the pump works with that setup. Then you know the pump is OK and the wiring is wrong.

The fix for a buggered up pump is this: Squirt some WD-40 or penetrating oil in the inlet. Tap it gently on the side with a hammer. Hook it up as above to a battery. It should click and spit out fuel, etc. If not--repeat and try again. If this doesn't work contact Mike at www.thingsunlimited.net for a used one.

Oh yea, one more thing--there will be a lot of fuel coming from the tank that you need to plug when you take off the fuel pump. And don't forget to change the fuel filter while you are down there.
_________________
'73 Thing--Ted
'77 Super Beetle Convertible
'87 Vanagon GL Syncro
'84 Mercedes 280 CE

[nthang]

Here is a helpful site: http://www.conservatory.com/vw/manuals_nyx/EberBN4.html .

I am looking for a link to Art Mavis, BN4 restorer and expert.....
_________________
NTHANG, LLC

[nthang]

Here is the guy that you want to talk to: http://members.aol.com/arkmirvis/heaterman.html .

He can do it all for you like nobody else with your BN4.
_________________
NTHANG, LLC

[fathing]

Are they still hot while connected to the pump? For a correct T/S you have to disconnect the wires from the pump and measure again. If both are still hot while the heater is turned on you have a short in your wires. Else it is just fine. Your pump works like a relay, therefore if the wires are on the pump while checking them for voltage you might get that reading because your (not properly working relay, aka) pump is shorting the circuit. I suspect the pump.
Clean the pump as 7thing3 suggests and get it to sound right. If it makes noise its a good sign. This doesn't apply to your valve train in your engine...

Cheers Dom

[scarroll]

Now I'm really confused! Before I got Dom's suggestion that the pump was shorting, I tried 7thing3's idea of connecting a separate power/ground source to the pump and seeing what it'd do. By golly, the darn thing worked great! A little squirt of fuel each time I made contact with power. So I hooked the pump back up to the heater wiring. Same problem! Both leads to the pump were hot! Damn! Then I read Dom's post and decided to put a continuity tester across the pump to look for a short...no resistance! The pump is acting like it's shorted, but it works great when I apply a separate power/ground in short bursts. So it occurred to me: Is the pump "relay" actually "made" (contact closed) until you let the circuit go to ground? That would explain what I'm seeing, anyway. If that's the case, my problem is that whatever device lets the current go to ground is not working. So, where is the switch gizmo that opens/closes to pulse the pump?

[7thing3]

I just did the following:

Unscrew the "cover" on the heater. There should be a white plastic plug (the only one of its type on the entire car!) with several wires on each side. There are 2 wires that lead down to the pump--brown/white and green. Hook your negative test wire to the brown/white wire and your positive test wire to the green wire. (I set my meter to 20 volts DC) Turn the heater on, you should see intermittent readings going from about -0- to about -6- as the unit supplies the pump with the juice.

I tried to get under the car but don't feel like doing that right now so I can't tell you what the wiring looks like down there (assume same as on top) or which wire attaches to which terminal but that should be easy enough-- + to pos wire, - to neg wire.

Also--when I tried to check continuity with the brown/white and a body ground it didn't work so maybe there is more to the relay than just providing + juice.

Keep us posted on your progress. I will check a few more things.
_________________
'73 Thing--Ted
'77 Super Beetle Convertible
'87 Vanagon GL Syncro
'84 Mercedes 280 CE

[fathing]

Did you check the voltage on the leads with the pump is disconnected? If you disconnect the pump and switch on the heater, what do you read on your Voltmeter? The brown lead is the ground. Now measure between each lead and the frame of your Thing. Brown to the frame must read 0, the other whichever color should read between 12.5 and 13.5 V. If it doesn’t you have to search the problem at the heater respectively in the wiring to the pump. I can assure you there is no device what makes the pump switch on and off to actually pump. When you applied external power to the pump it worked. That little pump draws quiet a bid of current so if you have bad corroded connections you get a high resistance and maybe not enough juice to make it run. Take two wires and hook them to where the original wires go to on the heater. (Somewhere I have a wiring schematic of the BN4, as soon as I find it I will scan it and post it here) The other end back to the pump. Run the heater and see if it is working now. If yes it’s the wires, else it must be the switching circuit e.g. the relay which switches the pump.

Good luck, keep us posted.

Cheers Dom

[scarroll]

I first got the pump to work by disconnecting the white multi-plug that 7thing3 refers to. I plugged two wires from a standby battery to the two leads that go to the pump...positive to green, negative to brown/white. I then switched the standby battery on and off. Every time I turned the power on, the pump would click and squirt a little gas.

Then, I wanted to see if I could get the heater to run while pulsing the pump manually. To do that, I had to put the white plug back together (other wires on that plug had to be connected). I knew that the green wire would be hot to the pump whenever the heater was switched on, so I had to figure out how to ground the brown/white wire in brief cycles. I could see that the brown/white wire connects to a short green wire (a different green wire than we've been talking about) on a terminal block on top of the heater, with that green wire disappearing into the heater's bowels. That green wire was hot whenever I turned on the heater. Therefore, I disconnected that little green wire from the terminal, and replaced it with a ground wire which I placed a toggle switch into. I turned on the heater switch, and started flipping that toggle switch on/off. By golly, the heater started to make that jet-engine noise after a minute or two, and I continued to run it this way until it put out some heated air.

Now, Lord only knows how close I was to an explosion by running the thing this way, but it did work. The part that I don't understand is how that brown lead gets to ground. It must do it via that little green wire on the terminal block, but I don't know what goes on when it disappears into the heater case. Dom, you said that there's nothing that turns the pump on/off, but it must cycle to ground in some way, shouldn't it?

By the way, thanks to both of you guys for detailed help on this; I really appreciate it.

[fathing]

I might be wrong , so I am looking for that BN4 wiring diagramm.
CU later... Dom

[fathing]

No I am not wrong , look at the diagrams. (Click on the image to enlarge it)

The pump is nothing else than a intermitting relay. While there is no power applied to it, it must read 0 Ohm, that means it is short to ground. As soon you apply power to the pump the relay (pump) switches itself off and therefore loosing power again. With no power it gets switched on again and so on. (Get it?) I am absolutely positive, your pump is shot. That’s it! Get a new or working used one. You can also install a toggle switch to keep you warm. Best thing is, if you run out of gas, just cycling that switch on and off by hand may keep you warm….

Cheers Dom

Guys, here is a good chance to download a good quality scan of a BN4 heater schematic. Do it!

[scarroll]

Dom, one of you guys referred me to that schematic a couple of days ago, and I looked it over carefully. Are you absolutely sure that it represents the same BN-4 that's in a 73 Thing? The reason I'm asking is that on this diagram, the brown (with white stripe) wire from the pump goes directly from the pump to ground. But on my Thing, the brown/white wire from the pump goes to a terminal on the top of the heater, which connects to a little green wire that enters the heater case. The diagram shows no such connection. Also, the diagram shows the green wire from the pump connecting to the thermostat. On my Thing, the green wire from the pump connects (via the white plug discussed by 7thing3 earlier) directly to the main power fuse on the heater.

The diagram you refer to makes sense if the pump acts like a flasher relay, which would cause it to pulse automatically. All I can say is that my pump isn't wired like this schematic. Maybe my wiring is all goofed up by the previous owner, but it sure looks original to me.

[7thing3]

There are 2 different style fuel pumps. The North American 1973 models (I assume that is what scarroll has) uses a intermittent style pump. I believe the schematic refers to the diaphragm pump that was used elsewhere in the world and possibly on busses, etc. Additionally we have a combination glow plug/spark plug, the schematic references 2 separate plugs. Additionally I don't believe we have the fuel valve reference as # 20.

I believe his fuel pump is OK as it tested OK when powered directly. It receives its power when the fan turns and some points open up every so many revolutions (1/33?). Being in Switzerland Fathing may have an entirely different type of unit.
_________________
'73 Thing--Ted
'77 Super Beetle Convertible
'87 Vanagon GL Syncro
'84 Mercedes 280 CE

[fathing]

Please define intermittent style pump. Scarroll trust me, your pump is bad. They didn't make a difference between old and new world BN4's. However they changed in time. Between 1969 and 1979 they installed 3 different BN4 heater in the Thing. That schematic is general. The heater was installed in the Type 4, 411 and 412 and as an option in the bus. Now back to Scarroll. That brown/white wire goes to a ground terminal where all brown wires go to. Look at them, the brown wires are all tied together, brown IS ground. Now please disconnect your pump, switch on the heater and measure between the green and the brown/white. I bet you read around 12V. Now measure between the green and ground, guess what? you will read 12V. Now measure between the brown and ground, 0V.

Now switch to Ohm (resistance on your meter) measure the resistance between the two pump terminals. You will have a very low reading maybe even 0 Ohm. Now imagine your wires on the pump. Doesn't it make sense now? While the pump is shorting the green wire to ground you will read 12V on the brown white wire to ground. Put any other electric device to the terminals like a light bulb. If you turn the heater on the light will come on.

An intermittent style pump is the same as a diaphragm pump. Also the stock fuel pump is a diaphragm pump or intermittent style pump. The difference is, the stock fuel pump gets mechanically actuated by your engine and the BN4 pump gets electrically actuated by a magnet (or relay). A Facet fuel pump is the same. Makes the same stupid noise. Do you need a device which controls a Facet fuel pump?? I don't think so. Scarroll, your pump is dead.

Cheers Dom

[7thing3]

I agree with the general premise that you should hook up your voltmeter (or test light , or any 12 volt powered thing) to the wires that lead down to the fuel pump. And this should be done without the fuel pump being attached as it could affect the reading if it is shorted, etc. If you get 12 volts or something close then you know the wires leading to the pump are OK and the fuel pump is an issue. Keep in mind it should bounce from 0 to 12 (in my case it was 6 but maybe my voltmeter isn't quick enough to respond) as the current gets shut on and off. If you are using a test light it will go on every time the heater sends the current to the pump.

When scarroll said both wires were reading + I just assumed he tested them with the pump disconnected. Upon reading fathing's latest post I understand better where he is coming from that the pump could cause the problem with both wires reading +.

Sounds like you are close to getting your heater going. Too bad you won't need it for another 6 months!
_________________
'73 Thing--Ted
'77 Super Beetle Convertible
'87 Vanagon GL Syncro
'84 Mercedes 280 CE

[fathing]

I admit it 7thing3 is absolutely right. After further detailed inspection of my own heater and the wiring diagram I found that Contact breaker (3) which triggers the spark plug and the current to the pump. You will not read exactly 12 Volts it will be less due to the intermitted current flow. However the brown/white cable is ground. The heater uses a glow plug and a spark plug to ignite the fuel. A single control relay (labeled CR) controls the fan motor and fuel pump. There are several safety circuits. Battery voltage (12V) is available at all times to the heater.
When heat is desired, the ON/OFF switch (or timer) is closed and relay CR operates. Assuming that the heater is in the cold state, the thermo-switch is closed to the NO (cold) terminal. The path thru CR (term M & J) and the thermo-switch energizes the glow plug. The fan motor also starts at this time. There are two fans. One pulls in combustion air and the other blows room air over the heat exchanger. The spark coil is also energized . While the glow plug is heating, the flame safety heater also is energized. If combustion does not take place in a reasonable time (2 to 3 minutes), the heater will be shut down (by de-energizing relay CR) and no more fuel will flow. After waiting for the safety switch to cool down (1 minute) the reset lever may be pressed to restart the heater.
While the glow plug is heating up, the fuel pump begins to deliver fuel. The fuel pump is a solenoid operated device. A set of points on the fan shaft open and close (thru a reduction gear) and trigger the fuel pump solenoid on and off. Each pulse of the solenoid delivers a tiny quantity of fuel to the heater. (Note that the solenoid is polarity sensitive; if the wires are reversed, it will not pump.)
Fuel quantity is adjustable by turning the threaded fitting on the pump discharge side. Screwing it in will decrease fuel quantity.
The fan shaft also has a set of points to operate the spark coil. Worm gearing from the shaft rotates the cam for the fuel pump trigger contacts. The fuel pump trigger occurs once for each 33 spark impulses. When the glow plug reaches operating temperature, the fuel should begin igniting. The thermo-switch senses the increased temperature in the heat exchanger and its contacts switch over. This opens the path to the glow plug and also to the flame safety heater. Combustion continues without the glow plug.
The spark coil continues to provide spark impulses as long as the heater is running.
The heater will continue to operate until the operator switches off the power or the Temp Regulating control (Temp Reg) opens the circuit. In either event, CR will drop out, stopping fuel flow. The fan continues to run, however, to purge the heat exchanger. The fan obtains power directly from the thermo-switch.
When the heat exchanger cools down, the fan stops as the thermo-switch changes over to the Cold position. Now the heater is set to re-start if the ON/OFF switch is closed. The heater will cycle on and off automatically under the control of the Temp Reg control. Each time, the fan will continue to run until purge has been completed and then the glow plug will re-energize in preparation for another ignition cycle.
The safety fuse is built into the heater. In case of control failure and subsequent over heating, the Over-Heat thermal switch closes. This short circuits the Safety Fuse directly to ground. The fuse blows and the fuel pump can not receive power.
Scarroll, maybe its only the polarity, the pump solenoid is polarity sensitive; if the wires are reversed, it will not pump. Next steps: Check polarity on the pump! This could be it, then according to your measurements there is power to the pump, this implies that the fuse is good and the rest of the safety devices are working as well.
Maybe this drawing helps further to locate your problem.

Cheers Dom

[7thing3]

I think I meant metering pump, not intermittent pump.

By the way--that has to be the most comprehensive and detailed description of the BN4 ever posted on the Samba. Well done!
_________________
'73 Thing--Ted
'77 Super Beetle Convertible
'87 Vanagon GL Syncro
'84 Mercedes 280 CE

[scarroll]

Guys, I think I know what the problem is. Dom, your last schematic shows a "trigger" that you describe as a set of points that open and close to pulse the pump. It looks like those points have to close in order for power to flow to ground. I believe that my points are not making good contact when they close, so power never gets to ground. I have confirmed this by running a ground wire (with the toggle switch that I described earlier) to the pump's brown lead, and flipping the switch on/off. The pump pulses, the heater makes hot air, the whole shebang. (How do you spell shebang?)

If I'm correct, I need to get to those points. Do I have to remove the entire heater and take off those end caps to do that? Do you guys think I'm completely nuts?

7thing3, you mentioned that the North American heaters are probably different than the stuff in Dom's part of the world. I think you're right, and that last schematic that Dom sent us kind of confirms that. You are also correct that I'll stay plenty warm wiggling that toggle switch as I'm tooling down the road.

[scarroll]

Guys, I think I know what the problem is. Dom, your last schematic shows a "trigger" that you describe as a set of points that open and close to pulse the pump. It looks like those points have to close in order for power to flow to ground. I believe that my points are not making good contact when they close, so power never gets to ground. I have confirmed this by running a ground wire (with the toggle switch that I described earlier) to the pump's brown lead, and flipping the switch on/off. The pump pulses, the heater makes hot air, the whole shebang. (How do you spell shebang?)

If I'm correct, I need to get to those points. Do I have to remove the entire heater and take off those end caps to do that? Do you guys think I'm completely nuts?

7thing3, you mentioned that the North American heaters are probably different than the stuff in Dom's part of the world. I think you're right, and that last schematic that Dom sent us kind of confirms that. You are also correct that I'll stay plenty warm wiggling that toggle switch as I'm tooling down the road.

[scarroll]

I forgot to tell you one other thing: I put a test lamp, ohm meter, and continuity tester on that little green wire that must be coming from the points. There is absolutely no indication of pulsing, either when connected to power or ground. That was my other clue that those points must be haywire.