Eberspacher BA6 Gas Heater

This article was posted to the Vanagon list by Jack Reed.


This is being written for all those that want some heat in their air-cooled vans. It's also written for those that just want some info on gasoline heaters before taking the plunge, either by doing it yourself or by having someone else install it for you.

------------------------- OBLIGATORY DISCLAIMER -----------------------

Before we proceed I'd like to offer a few words of advice concerning gasoline heaters. THEY ARE VERY DANGEROUS AND CAN BURN YOUR VAN WITH YOU IN IT TO THE GROUND IN A MATTER OF MINUTES. IF YOU DON'T KNOW WHAT YOU'RE DOING, SEEK OUT A MECHANIC OR DEALER THAT DOES. Sorry I had to shout, I just wanted to make sure that everyone was paying attention.

All kidding aside, these things can be very dangerous if they are misadjusted or if the safety interlocks are broken or defeated. I have heard of older units that had no safety interlocks built into them whatsoever. I would be very cautious about having one of these units installed in my vehicle for the simple reason that you, the driver, are then responsible for ensuring that everything is always in proper working order. If someone else installs such a unit for you, you may not be capable of determining when a problem with your heater occurs, with possibly disastrous side effects.

One other note before we proceed. I installed an Eberspacher BA6 heater in my 1981 Westfalia from scratch, which means that there was no heater in the van when I started. The rest of this article refers to the BA6 since it's the only heater I have any direct experience with. You should be able to draw certain references about general heater operation from this article but be careful about making assumptions about your unit if you determine that it's decidedly different in operation from the BA6.

All comments and observations in this article are from personal experience and recollections. Refer to the appropriate manual for your heater for exact specifications, troubleshooting tips and maintenance guides. This article is meant to be a general info guide only for the DIY heater mechanic/installer and for those interested in learning more about their operation.

Before I talk about the installation phase, let's talk first about general heater operation. A gasoline heater is really a very simple affair. Basically they are nothing more than a carburetor, since they employ a simple metering system for fuel delivery, a spark or glow plug for ignition, a means of delivering intake air and exhaust of spent gases. Surround the whole thing with safety interlocks and you've got a gasoline or diesel heater.

Each manufacturer (Eberspacher, Stewart-Warner, Southwind to name a few) has a slightly different way of accomplishing these tasks. This article is going to concern itself only with the Eberspacher (or Espar as it's known in Canada and the US) BA6 which was originally installed in early air-cooled Vanagons.


The BA6 has several different "packages" associated with it. By packages I mean blocks of components that are installed in certain specific parts of the van. The most important part of the installation is, of course, the heater itself. This is a long, flat pancake made of sheet metal that basically consists of two parts, the inner shell and the outer shell. Think of it as two clams, one inside the other if you're having trouble visualizing it. At one end is where the combustion motor fan, the spark/glow plug, the inlet for the fuel from the fuel pump and the temperature regulating sensor reside. In the middle are the flame and overheat switch and at the other end is the exhaust pipe.

The combustion motor fan does two things, supply air to the combustion chamber by means of a rotating, finned fan as well as supply the signal to the fuel pump and the ignition coil by means of a set of points that are tripped by a cam on the end of the motor shaft. The Bentley manual gives directions for adjusting the fuel pump by the number of "ticks" of the points, but as we'll talk about later, this method is only good for sea level installations. The fan pulls outside air through a 2' corrugated plastic pipe that plugs into or connects to a hole in the rear crossmember. Great care must be taken that this plastic pipe is secured at both ends, otherwise vacuum could be created at the combustion motor fan inlet by air rushing by. This would cause the flame that normally is contained in the heater to be pulled outside of it, which could cause meltdown of your heater, your van and you.

As just something else to go wrong (not really), the combustion motor fan has a little "propeller" on the end of the fan itself that creates a long flame path in the heater to ensure complete combustion. If this propeller is not in place because it was burnt off by an incorrectly adjusted mixture, you'll have to find/buy another. Otherwise it's impossible to get your heater adjusted properly and you'll find it's operation intermittent at best, inadequate at worst. I've been told that these fans are "mated" to the motor and that replacing just the fan will cause premature wear of the bearings, resulting in a $200+ replacement. This is reason enough to ensure that your heater is properly adjusted at all times.

The spark/glow plug is just that, a spark plug that sits in the stream of gas from the fuel pump. It has its own ignitor or ignition coil that also gets its signal from the points in the combustion motor fan. The spark/glow plug consists of an inner electrode, exactly like a spark plug and an outer shield that looks like a small, drilled tube. Even though I've never seen one in action, I assume that once the spark gets everything nice and red hot, the shield just serves as a secondary ignition source for the fuel.

At the base of the spark/glow plug inlet is a short metal tube that receives the outflow from the fuel pump. By having these two points essentially coincide, the designers ensured that all fuel would be burnt as completely as possible. Even so, these units were not designed with emissions in mind, although I have heard of mechanics that used their CO machines to adjust the fuel pump, hingeing on the 14.7:1 ideal air/fuel mixture. I haven't been able to convince my dealer to let me use his CO machine for this purpose yet due to the excessive heat generated at the exhaust pipe.

Which brings us to the other end of the heater, the exhaust pipe. This pipe is bent in a 90 degree angle so that the exhaust doesn't shoot directly at the end of the transmission. About one inch past the end of the pipe itself is a metal cap, roughly the diameter of the pipe, which is held in place by two metal straps that connect to the end of the exhaust pipe. This pipe is there to ensure that the exhaust does not ignite leaves, etc. that rest underneath the van. There have been documented reports of this occuring so make sure that your exhaust pipe is in place and has the cap as well. If the cap is missing or damaged by some fumble-fingered parts yard mechanic like mine was, you can easily fashion another using pop rivets, iron strap, and a small circle of 1/16" to 1/8" iron. Don't use sheet metal for the cap, the heater will burn right through it. An additional benefit of the cap that I've only surmised and never really researched is its action as a venturi. The flow of air between the cap and the end of the pipe creates a natural vacuum that creates an increased draw of exhaust through the heater. I'm not sure if this is true or not, but it's likely, so make sure that your cap is in place.

In the middle of the heater is a contraption called a flame switch. The purpose of the flame switch is to provide a signal to the control unit that the heater is up to temperature. This signal is provided by a micro switch that is tripped by an expanding metal shaft that resides in the heater's core. The flame switch is tricky to get adjusted properly, as the micro switch is held inpositon by two screws terminated by nuts. The only way I've ever been able to get mine adjusted correctly is by using a propane torch and a DVM. Once I've got the micro switch in what I thinkis the correct location, I lock down the screws as tight as I can get them. Then I set the DVM on the OHMS position and place the metal rod in the flame from the torch after hooking the DVM to the common spade clip and the NO spade clip. If the meter shows infinity when the rod is cool and ~0 when in the flame for a few seconds then you've got it right. The rod can get red hot pretty quickly while in the flame from the torch so be careful where you place it when you're done checking the adjustment.

The flame switch adjustment has been at the heart of 90% of the problems I've had with my heater, so make sure you get it right. If you're unclear on what's happening there or how to follow my directions, write me at the address at the end of the article and I'll give you a hand with the procedure. The other 10% of the problems have been due to an incorrect mixture, which resulted in the premature demise of my first combustion motor fan. This resulted in incomplete combustion of the fuel and erratic operation of the heater. Information is provided on adjusting the fuel/air mix for your unit later on in the article. There is also a metal "button" in a ceramic ring that fits beneath a clip on the top of the heater. This is called the overheat switch and it's nothing more than a breaker that will kill power to the heater if the temperature of the heater's outer "skin" gets too hot. This could happen if the fuel pump were to lock in an open state, allowing unrestricted fuel to create a "runaway" situation. It's your final defense against meltdown so make sure that it's in good condition by running the checks recommended in the manual.

The two halves of the heater are held together by the use of rivets. If any of yours are missing, pop rivets can be used to resecure the unit. The heater itself works like any home furnace you're familiar with where the actual combustion occurs in the inner jacket (or clam, if you're still using that image as a guide) which then heats the air in the cavity made by the second jacket (or clam). The exhaust pipe runs through this outer cavity to get to the outside of the heater. Warm air is pushed through this outer cavity by means of two fans, the squirrel cage on the end of the alternator and the auxiliary fan that draws air through a hole cut in sheet metal underneath the rear seat. The auxiliary fan pulls the air from the heater boxes that surround the exhaust manifold and the squirrel cage fan pushes air through them. Another plus (besides the added boost of warm air) provided by the auxiliary fan is that by drawing air from underneath the rear seat it's recirculating warm air that's already in the passenger compartment. This means that the heater doesn't have to continually supply heat, it only has to replace the heat lost to air leaks and convection losses through the body, roof and floor. I live in Colorado and these losses amount to a lot when it's 20 below outside and you're scooting down the road at 65.

The fuel pump is a small, 4" affair that connects to the fuel line after the fuel filter. Make sure that you get the "tee" for the main fuel line and the clamps that hold it in place, you'll need them to splice into the main line. I've heard the fuel pump described as nothing more than a hypodermic in its operation because of the way that it squirts gas down the hose the heater. It attaches to the cross member by means of a rubber bushing and a nut and bolt.

At the front of the heater is a temperature sensor. It's a criss-cross arrangement with a resistor in the center of it. It's used in conjunction with the thermostat to regulate the heater's output temperature. The sensor sits in the output stream to the passenger compartment at the front of the heater.

The final part to the heater section is the belly pan, a long, wide section of pressed sheet metal that runs from the gas tank to the transmission and between the frame rails. The belly pan serves two functions, it protects the heater and its components from rocks, salt corrosion, etc. and it traps "some" of the heat produced by the heater. There's a small door in the center of the belly pan to give you access to the flame switch. There's also a cutout in the sheet metal to allow you to adjust the fuel pump without having to remove the belly pan. I've often thought about insulating the belly pan to reduce heat losses, but haven't only because I can't figure out why VW didn't insulate it in the first place. I suspect there's a good reason for this and until I find out what it is I'll live with the heater in its present state. If someone has an insulated belly pan in use for several years I'd appreciate hearing about it.

Last (didn't I say "final" in the last paragraph?) but not least are the two short sections of duct that connect the heater to ductwork at the front and rear of the engine. These pieces of duct are needed to splice the heater into the old, single pipe that used to carry heat direct from the heaterboxes to your frozen tootsies. The ducts should be in good shape, with no cracks or breaks in them. Suitable replacements could probably be gotten from a heating/ventilating shop if the dealer's prices are too dear.

If after you've got the heater installed and running, it sounds like a locomotive has taken up residence there in the van with you, the inner jacket is cracked. You need to get another one since I'm not sure if such a crack can be repaired. I'm not saying it's impossible, just that I've never had to have it done so I can't say whether it's possible or not. In any event, the heater is unusable until you get it replaced or repaired since carbon monoxide will be venting directly into the heated air flow to the passenger compartment. Just in case no one's told you by now, carbon monoxide will kill you, either by depriving you of oxygen or by causing you to fall asleep at the wheel.

The person that told me about this sound being produced by a crack said there's no mistaking it from the normal sound of the heater in operation. If you're not sure if yours is cracked or not, but suspect it may be then have a heater/ventilator guy or gal probe the output from the heater in the passenger compartment with a CO sniffer for excessive fumes. I can't caution you enough about this. It's better to freeze then to die from carbon monoxide poisoning and possibly kill other innocents in the process. In fact, after all is said and done, it's probably not a bad idea to have someone probe the heated air for CO as a final check of your work.

That covers the components directly associated with the heater itself. Let's move to the back of the van now, in the cavity between the bottom back of the rear seat and the engine. A hole needs to be cut in this sheet metal to allow the auxiliary fan a place to pull air from. Make sure when you get your heater that you get the plastic cover and foam gasket that the fan mates to. You can use the cover as a template when it comes time to cut a hole in the sheet metal. There are two "dimples" in the sheet metal that you can drill out to receive the screws the hold the cover in place. Once you've got the hole cut find a logical place to hang the auxiliary fan from so that it will mate to the port that juts out from the cover.

Next you need to replace the ductwork that routes hot air from the control flaps to the original duct to the front of the cab. These two units are almost identical, the only difference being a port to hook the auxiliary fan onto. This is pretty straight forward, just check that the one-way air flaps in the ductwork are in place and functional, otherwise part of the pressure from the fan will just wind up fighting against the pressure from the squirrel cage fan and you'll wind up with zip for heat. While you're back there it's a good idea to R&R the control flaps so as to get maximum heat out of the heater boxes.

The last package of components are those that fit under the dash. Although these components can be installed without pulling the dash, it makes for a much cleaner, easier time of it if you do pull it prior to installing them. There are five main parts to this phase, and we'll hit them one at a time.

First there is the extension to the fuseblock that holds the two additional fuses for the heater's operation. Didn't get it when you pulled the heater? You can use the appropriate sizes in in-line holders instead.

Next is the timer/thermostat, it goes in a hole in the dash just below the instrument cluster and to the right of the steering column. If there isn't a dummy hole already in place try and pick a spot where you'll have room behind the hole to mount the thermostat. The timer section of thethermostat allows you to preheat the heater on a cold Winter's morning. Don't run the heater off the timer more than once when it's real cold or you take the chance of running the battery too low to start the engine. Press in on the knob with the "+" on it and turn it to the right, you should hear the watch mechanism ticking merrily away. If not then something's jammed the works and you'll need to take it apart to get it working again. It's not absolutely critical that this section of the part works, so don't sweat it too much if it's broken. Normal means of heater actuation is to turn the knob to the right without pressing it in first.

Then there's the safety switch, which mounts there by your right knee when you're sitting in the driver's seat. It has a bimetal relay that will "blow" if the heater doesn't come up to temperature fast enough or if it doesn't keep putting out heat after the flame switch rolls over to its "closed" position.

After that there is the heater relay which makes an audible "snap" when the heater kicks on or cycles. That goes over in the area behind the glove box. Last but not least, you need to replace the heater levers there in the dash. The replacement lever assembly has a contact on the right or "HOT" side of the lever that supplies a ground signal to the electronics package. I suppose that someone could bypass this step and just install a toggle switch in it's place but care would have to be taken to ensure that the temperature control lever was in the "HOT" region before the heater was actuated. Otherwise heat from the heater boxes would be cut off.

I'm not going to go into all the checks associated with these components by duplicating the work the Bentley technical writers put into the manual. Suffice to say that you should pick one up and run the checks that they recommend. If you can't afford the manual (and at $90+ a pop who can?) there are several outfits that will sell you a copy of the heater section of the manual for around $10. Or find someone who has a copy that is willing to make you one. I don't have one. Nope, not me, uh uh, don't ask. Well, I don't know, maybe if you ask real nice.


Installation is pretty straight forward if you take your time and start sometime in June. If you wait until September when the first flakes start flying you'll probably make a mistake and fry something that you can't afford to replace. Try and start early if at all possible. I performed the installation in three phases: underdash components, engine area components and under van components. Check your work as you go and replace anything that looks borderline like rubber boots or fuel lines. If you have the room and the tools, check each component for proper operation by hooking them up to 12VDC or by performing whatever resistance checks you can before installing them. I laid everything out on my garage floor and made sure that I knew where all the wiring and connectors went before I started the install. Then I visualized how everything hooked up, where it was located in/on the van and how best to route the wiring. Once that step was done, the rest just fell into place.

Uh huh. Believe that and I've got a bridge to sell you. This is a painstaking labor of love that will easily consume at least three weekends over several months before it's right. But yourwife/kids/friends/frozen nose will thank you for the time spent doing it right. I'm sure that someone could install a BA6 faster than that, but that's how long it took me and I've spent 24 years crawling around all sorts of vehicles. If your level of expertise is less than that you may want to start in April (just kidding). I don't feel that this is too much of a job for anyone with a fair degree of mechanical/electrical understanding. But you will use all of that knowledge and then go looking for more, so don't rush the job if you don't have to.

When it comes time to mount a component to the body, such as the heater or the safety switch, look for little "dimples" in the sheet metal. This is where you need to drill a hole to accept the screw for that component. Be careful of punching through whatever is behind the dimple so thatyou don't, for example, punch a hole in the van's floor. The bushings that the heater hang from will probably get trashed by whoever pulls the heater, mine were. They run around $1.50 each from the dealer and I'd suggest that you install them as they will isolate the heater from road shocks and bumps.

Items to check when inspecting a used heater are:
- No worn-through rust patches, in fact no holes at all.
- No big dents, the inner shell could be collapsed.
- Good bearings on the combustion fan, with little or no play to them.
- Points in combustion motor fan are in good shape (pull the end cap to check them).
- Apply 12V to combustion motor fan to check operation, keep your fingers, hair clear of the fins when performing this step as it runs at ~7000 rpm.
- That combustion motor fan does not show signs of excessive heating and that the little propeller on the end is intact.
- Correct resistance on the ignition coil (check Bentley for specs).
- Spark/glow plug electrode and shield are in good shape and aren't burnt or melted away by excessively high temperatures.
- Apply 12V to the fuel pump, if it doesn't "click" it's probably NG.
- Apply 12V to the aux. fan to check operation, check it's bearings also.
- Rubber hoses to/from the fuel pump, replace if cracked.
- High tension wire to spark/glow plug, replace if not perfect.
- Plastic pipe to combustion fan has no cracks and seals well to crossmember receptacle and combustion motor fan inlet pipe.
- That flame switch rod is straight, micro switch adjustment correct.
- Inspect ductwork for cracks, repair with hi-temp silicone, epoxy, etc.
- That all electronic components pass recommended electrical checks.


Here's the part you've all been waiting for, adjusting the fuel/air mix (which is why I put it at the end of the article, naturally). The manual states that 18.4 to 21.7 cubic cm. of fuel should be dispensed every 200 ticks of the fuel pump. I did this and the heater smoked liked a runaway freight train. Due to the nature of the beast, that being that these heaters are nothing more than big carburetors, they have to be setup for altitude. Since there's no timing adjustment you can only throttle back on the fuel to accomodate the lower oxygen density at higher altitudes. If you're in the mountains (I'm at 5,280') then you want to keep throttling back on the fuel pump until the heater stops smoking. Leave the heater at this setting for a week or so then check the tabs and propeller on the end of the combustion motor fan. If the tabs, etc. show signs of being burnt you need to richen the mixture a little so as to cool off the charge. If you get things too lean you'll fry the fan and the heater won't work very well if at all, so keep checking the state of the fan until you're happy that it's not getting toasted.

The only other way to adjust the heater properly is by use of a CO meter. I'd suggest using a length of muffler pipe on the end of the exhaust pipe so as to cool off the effluent as much as possible. Otherwise you take a chance of frying the probe on the dealer's $15,000 emissions machine. And he won't be very happy about that. If you can get someone to let you use their machine, set the heater at 1.5% CO, which is the ideal stochiometric ratio of fuel to air. I'd still check the fan a couple of weeks afterwards just to be on the safe side. But I've already roasted one fan so I'm a little more cautious than most. Those things are hard to find and you'll pay dearly for one when you do.

That's it. Pick a nice shady spot to do the installation and take your time learning how the whole thing works and goes together and you shouldn't have any problems. I can be reached by email at yojak@co-op.com if you have any questions about the installation, etc. Good luck and enjoy your old rolling icebox turned four season Van!

Posted July 27, 1995.

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