Gas Heater Question

Jan Peter de geus · Post by **Jan Peter de geus** » Mon Dec 04, 2006 6:52 am

The BA4 manual indeed gives several values. Section F1.1, description of heating system, page 4-5, on which the pump is described, gives a value of 11,8 - 12,5 cc for 200 strokes. This is in agreement with section F1.3, checking parts and adjusting, page 2-5, technical data, where it talks about cc/2 min. and gives measusures for the RPM band of the combustion air motor. If you take, e.g. 6600 rpm, divide by 33 (the pump gets one pulse every 33 revs of the combustion air motor) you will have 200 pulses in a minute, yielding 11,85 - 12,5 cc/min (23,7 - 25,0 cc/ 2 min). The confusion sets in at the previous page, 4-4, where indeed they write 24-25 cc per minute at 6000 rpm of the combustion air blower.

Conclusion; in 2 sections the authors mention equal measurements, in one section they mention the double amount. Now you state your heater finally worked fine with 12 cc/min. So, I would tend to believe this is about the right amount and the book is wrong on page 4-4 of section F1-3.

I am not aware of a fuel filter in the heater circuit. I sure do not think I have ever seen one in my car. I did see in the manual there is a tiny stainer at the incoming side of the pump. I cannot help you with the "polarity" question. If the pump is not reversing the way it pumps when you change the wires it probably doesn't matter how you hook it up.

Cheers, Jan Peter

raygreenwood · Post by **raygreenwood** » Mon Dec 04, 2006 11:32 am

Yes, there is a polarity listing on the pump wires. But i do not know if it matters. This pump is actually a solenoid.
Generally on fuel pump output volume I start at the least end...and work my way up. If you set it too lean, you end up having to turn the knob up too high toachieve good heat and then have no reserve position for the really cold night. Also running too lean means that the heater will not cycle offand on. It must run constant (pumping and igniting) to keep up with the heat setting if its too lean. This causes very high wear to points and glow plug.
But...you do not want it so rich that either the overheat switch is popping, or when stationary in traffic, the volume of exhaust is such that it is sucked back into the intake on the back engine lid. If you are smelling exhaust or fuel...you either are running too rich or have a leaking o-ring at the blower.

There is not a fuel filter inline...but there is a small odd looking plastic fuel accumulator bowl...which could look something like a filter. It is in teh return line from teh fuel injection and this is where the heater fuel pump draws its fuel. You must have it...or there will be feed problems. Ray

wildthings · Post by **wildthings** » Thu Dec 07, 2006 7:46 pm

Well I got a cover made today for the hole I drilled over the heater to access the fuel line and have new hoses for the aux fan. Untaped some more of the wiring harness and found the wire which originally supplied power to the heater so now it is spliced in and the unit is hopefully 100% except for not having the accumulator/"T" thingy which I have no idea where to get. As a side benefit I also powered up the relay for the rear window defroster though I haven't checked to see if it works yet.

Still need to get my studded tires on and replace the thermostat cable on the engine. Then I hope I can make the winter with nothing more than an oil change.

raygreenwood · Post by **raygreenwood** » Fri Dec 08, 2006 7:03 am

What works well in place of the accumulator "T"....is any small plastic Japanese fuel filter with two outlets or inlets. You know the type...bowl or "acorn"shaped with one line in on the bottom and two lines out at the top. I think these came on like 70's to 80's toyotas and datsuns of all types. Since they are for low pressure .....mostly carbed...they work great. Ray

MGVWfan · Post by **MGVWfan** » Tue Dec 12, 2006 6:30 pm

My $0.02 US. I have a '73 412 wagon, and after putting a new A/C compressor, running that blasted right side air hose became difficult, especially since the VWoA port-installed heater plumbing (installed when they put the original AC in) just didn't work with the new config. The original "Y" thing would have worked great, but I don't have one. So, to get the heater back up and running, I plumbed the blower outlet (don't forget the non-return flap in the blower housing) directly to the left heater box inlet tube, and taped over the right box inlet tube with aluminum duct tape. Since both left and right air inlets at the Eberspaecher dump into a common chamber around the combustion chamber, and the outlets come off the same chamber, it doesn't matter if you've got flow in both inlets, as long as there's enough flow to take away the heat being produced. So far, so good, no limit switch tripping, and the "flame feeler" appears to be taking about the same time to close as before.

wildthings · Post by **wildthings** » Wed Dec 13, 2006 10:28 am

I have everything hooked up and working well at present. Though I have been thinking of trying to use a single outlet fan from a square back and just feed the left side, wasn't sure if I could get away with feeding only the one side. Thanks for the knowledge. The single outlet fan is larger than the double outlet and I would think that maybe I would get a more noticable flow to the defrosters while the engine is off or at idle if I used it. Wish I didn't need the fan at all, on my bus I removed it long ago as an unnecessary hinderance to engine access and eventually used the relay and wiring to instead power an inline fan that doubles the air flow, but with the gas heater on the 411 the original pusher fan is a necessity. I had a nice little snap in metal cover for the right side that I had been using to block back flow when there was no fan installed. I tossed it into my VW odds and ends box for some future day.

For Ray, I saw in the parts book that they call that "T" thingy in the fuel line to the heater a deaerator. Not sure where any air that gets deaerated goes? Was the "T" installed with the pump outlet down so the air would work back up into the return line? They also show just using an inline filter as an alternative.

raygreenwood · Post by **raygreenwood** » Wed Dec 13, 2006 11:32 am

That is the function of it...but the most approproiate name is actually an accumulator. Its purpose is to make sure that there is a reservoir of fuel as the return line from the EFI tends to drain down to level when you turn off the engine. Ray

wildthings · Post by **wildthings** » Fri Dec 15, 2006 11:34 pm

Well the heater is working great, except that it appears to be full of oil. Smells just like regular heater boxes do when you have a leaky engine. Seems to be getting much better with time, but the first time I really got it hot I had oily smoke coming out of the vents, yck!

I guess some previous owner must have had bad engine leaks for a long time and some of the oil eventually moved from the engine heat exchangers on into the non working gas heater. Hopefully in a few more days the last of the stink will be gone.

MGVWfan · Post by **MGVWfan** » Sun Dec 17, 2006 5:09 pm

Yeah, I get the same thing with mine, even though I keep the engine clean, no major leaks (just a little annoying seep at the rear), the hoses and plastic tubes are all intact and tightly clamped, and I rinsed the heater's heat exchanger (the hot air side) with paint thinner when I had it out a few years back. Seems to smell and stink the first time it runs for more than 10 minutes at a time (like when the outside air's below 40 deg F). Just running it a few minutes every month doesn't seem to keep it from stinking.

raygreenwood · Post by **raygreenwood** » Mon Dec 18, 2006 8:28 am

Just be sure what smell you are smelling when it "stinks". There are a couple of ways that combusted fuel vapor gets into the airflow for the cabin. If you have not checked these spots....then you may actually be smelling exhaust smoke.
(1) The blower unit has an aluminum nozzle/shell. The clamp ring must fit tight and the proper o-ring must be installed between the aluminum nozzle and teh heater flange. I put 600F permatex copper sealant bewteen the aluminum cone and the blower body. Then a bit more on the o-ring (also use a silicone o-ring). Then clamp and let dry for 24 hours.
(2) Make sure you have poked no holes in teh woven mantel on the inside of the burner chamber.
(3) make sure the nut on the thermocouple probe is tight.
(4) make sure there are no gaps or rust spots around the tail pipe clamp.
These are all potential exhaust leakage points. Ray

wildthings · Post by **wildthings** » Mon Dec 25, 2006 6:02 pm

I replace my aux fan motor today with a larger one out of a bus. It puts out a noticable amount of additional air over the original fan, roughly about 50% more at idle. The bus motor is physically larger and the bus fan has more vanes than the 72 411 fan/motor combo. I kept the original 411 volute which bolts the the cool air intake, and install the bus motor and fan into it. Not quite a bolt in change, as the distance between the surface of the mounting flange and the far edge of the fan is slightly different, but it was an easy alteration.

Also now that I have been running the gas heater for a couple of weeks the burning oil smell has disappearred. !!!Hurray!!!