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Just when you thought you'd heard just about everything on Pearl's heater, along come something new.   And what's that?

Jealousy, pure and simple.  But we'll get to that.

The way my heater works is I turn it on and then set the desired cockpit temperature using a digital thermostat, just like you probably have at home.  The heater itself puts out a constant amount of heat, just like your home furnace (in fact, it is identical to a miniature home oil burner, nothing more) but I throttled mine back by leaning out the fuel to make it run cooler because I was afraid of getting it too hot.  After all, it was the first gas heater I had seen and I really didn't now what to expect.  Playing with it on the bench I could get an output temp of over 300ºF but I set it up to output about 180ºF, just like my Nissan Rogue.  That worked, but it wasn't overwhelming so I added something to bring it up to about 200ºF with a switch to toggle between the two output temps.

THAT all works well, but under 40ºF outside and with all of the air leaks in a Speedster, the 200ºF output is a little lacking and I kept thinking, "Wouldn't it be nice to be able to dial the temp I want just by turning a knob on the dash like my daily driver?

That's where the jealousy part came in - That's exactly how the gas heaters in Danny P. and Jack Crosby's car work - You turn it on, then dial in the amount of heat you want coming out.  When it gets too hot, just turn it down a little.  Too cool?  Turn up the heat.  Pretty simple.

My heater (a very low-tech version, to be sure) has a solenoid fuel pump that squirts a set amount of fuel for each stroke and it is driven by a little circuit that Danny P. made that produces a set number of pulses to the pump per minute.  You get more heat by running the pump faster within a range.  150 pulses per minute gives about 170ºF.   300 pulses per minute gives about 310ºF.  Pretty simple, but I needed a variable speed circuit as a driver for the pump and after a ten minute search on Amazon and next day delivery, I received this little gem (I show the USB thumb drive as a size comparison):


This is a pretty cool circuit that has nifty adjustments to fine-tune what you need.  It is tiny, as you can see, fully assembled and cost me all of $12 bucks, delivered the next day.

$12 BUCKS! 

I haven't begun playing with it yet, as I'm waiting for one more part (the MOSFET on the output side, Dan) and then I can start playing with it.  I suspect that I'll end up playing with component values on the circuit board to custom-tailor the pulse range to the 150 - 300-ish that I want, but that'll be the fun part.  Even more fun is that I may need some suggestions from the peanut gallery on component values once I get into this if I have to change things, so stay tuned and heads up @DannyP and @Michael Pickett

The idea is that this could replace the digital thermostat under my dash with a small box (size of a pack of cigarettes) with the on/of switch for the heater and a heat level knob for the fuel pump.  Simple and unobtrusive.

Can you tell that I'm getting a little bored from COVID and need something to do?

So far, there are three heaters working like mine (that I know of) - Mine, Cory Drake's (Danny's old heater) and Tyler in Seattle using the same circuit and pump as me in his VW Beetle (he saw my thread on the Samba and contacted me about it).  Mine is throttled way back, while Tyler's (Seattle) and Cory's, running faster, put out GOBS of heat, which they like.  Mostly, I'm doing this to mine so as NOT to be jealous of Jack and Danny any more.  And for something to do for a couple of days before cold weather hits.  And a way to have a more comfortable cockpit with all of the air leaks that Speedsters have.

Here we go again!


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Last edited by Gordon Nichols
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Ray, what Gordon is trying to do(and will succeed at) is a pretty simple thing. He just needs to vary the pulse speed of a square wave(on-off) at a 50% duty cycle.

Early BN-2 gas heaters had a diaphragm pressure regulator and a weird pump. Diaphragms fail, and there simply aren't any more. Mine worked for a while, but the fuel pump would overheat and then stop working. Or maybe the diaphragm cracked open, I don't know.

Late BN-2s have a solenoid fuel pump, and a set of points on the blower motor to turn the solenoid pump on and off and make it work.

Gordon and my former heaters are the early style, not a chance of using the OE fuel arrangement though. So what to do?

I found a later heater with pump. But the blower motor was non-functional. SO I have a later model pump, but an early heater.

I know, I'll use a 555 timer to make a simple pulse-modulation circuit to turn the pump on and off X times a minute. Simple really. So I made two, and mailed one to Gordon after I verified it works

An Arduino is way more capable than Gordon needs. An Arduino Mega runs Mike and my EFI. But it needs software written for it. I've written some C++ for them, and it's kind of a real PIA.


I know what you mean, if you can get a circuit already made it is a big bonus.  In my friends case he has coded Iphone apps, even used an arduino to do an intelligent, or smart blinking  3rd brake light, I guess each person has their favourite tools and skill levels '

He has helped me to do my cruise install and a few other, he can read a schematic in his sleep essentially and he modified and reduced the complexity of the schematic of my cruise down to only two bidirectional toggles ... It was great fun. 

Last edited by IaM-Ray

I've been messing with electronics since I was around ten. 

I've done a bunch of Basic, Pascal, and Assembler coding(which really sucks, BTW). I learned a little C++ just for Arduino. I've done servo control, a 4 thermocouple reader with serial communication of data to a remote reader and display with two separate Arduinos.

Now I find code, then copy and paste. Like my EFI, download and bootload the code, it's rather large. And then there's the EFI tester, another download. Not hard at all if you know where to find stuff, and can modify it to your needs.

I think what Gordon is doing is cool, but I wouldn't set the heater's output much beyond 180F. Things get too hot, and you're in a plastic car.

And THAT is why I throttled it back as much as I did.  It works, but is slightly luke-warm-ish.  Considering the time and components I need to make what I have perfect for me, buying this circuit actually saves me time and money.   Using this function generator I can much more easily set up a range of heat on demand by turning a knob.  Easy-Peasy.  It is very much like using a Coleman camp stove.  Start it on a low flame and then turn a knob to increase the flame to what you want.  It's kind of that easy, but instead of a valve creating more or less gas flow you have something that supplies little pulsed squirts of gas.  Run it faster and it squirts more gas and vice versa.

There are a few safety factors included, like a thermo switch that turns on a glow plug when the combustion chamber temp gets too low, a circuit breaker switch for when the combustion chamber temp gets too high and a circuit that keeps the combustion chamber fan running for a while after the heater is turned off to evacuate the chamber of any unburned fuel (although Dan's newer heater has a few more, like a circuit to watch for a flame in addition to combustion chamber temps - it's pretty sophisticated).  

Including a cabin climate control thermostat on mine has been pretty cool and it works great, it just needs a bit more heat output, but that was my own doing.  This new stuff will just be "Rev 01" of my (and Dan's) original work.  If it works, I can spec it out for other people with BN2 heaters with failing fuel pumps (see Danny's note of dead fuel pumps up above) and maybe resurrect a few more of them.  Without this approach you simply can not get BN2 fuel pump parts anymore.  

I, too, got my first Ham Radio license when I was ten and built my own transmitter, an Eico 720.  That was back in the days of vacuum tubes (1960).  In junior high ('64) Science Fair, I built a transistor logic demonstration using Dual J-K flip flops, the basic building block of digital computers (it's basically an electronically latching toggle switch).  Absolutely none of the judges understood what I was showing them.  

It isn't that complicated, gentleman. You all know how points work, correct?

On-off-on-off. Dwell is time in degrees around a circle, remember setting the point gap and then checking for correct dwell? Too small a point gap gives you too much coil on time, the coil can overheat. Too big was no good either. Too big and the coil may not fully charge: weak spark. You needed to adjust the gap just right to get proper dwell.

50% duty cycle just means equal time on and equal time off. The circuit Gordon is using(and just like my original 555 timer) generates a square wave, i.e. on(high) then off(low).

Instead of mechanical contact points, the signal is generated electronically.

Then instead of contacts or a relay, the on-off(square wave) signal is sent to a MOSFET(really a high-current) transistor/switch(instead of mechanical contacts). 

Gordon just needs to be careful, because the fan speed of the heater stays the same. I fear that as Gordon increases the fuel(and burner temp!) that the fan won't be able to remove the extra heat generated.

Last edited by DannyP

@Stan Galat wrote: 

 "I have no idea what you are talking about, but it sounds very, very cool."

This, from the man who methodically explained the heat retention characteristics of different viscosity fluids without ever sitting through a Thermodynamics class (Both Kathy and I had to take Thermo twice before we "got" it).  Different strokes for different folks.

Every generation needs a "Buckminster Fuller" or a Mary Grace Hopper or a Charles Bolden for inspiration.  Someone who looks at something, sees it lacking and then pioneers a solution to improve it, over and over again.  

Kind of like building the ultimate T-1 engine, eh, Stan?  Something I don't have the patience to do anymore.  Or others on here fabricating custom parts or systems (Like Piperato and Pickett) to make their cars better.  It's fun.

Electronic stuff is simply building blocks, like concrete blocks to a building.  They can be configured in different ways for different purposes.  You just need to understand how they fit.  I had no clue how this circuit worked, but looked into it, it made sense for my application and I'm learning as I go along.  And it's fun.  Besides - You can google "12 volt variable frequency pulse generator",  get a bunch of hits and go from there.  It's a great learning experience.

There are a lot of BN2 heaters out there that are dead because of the lack of fuel pump diaphragms which are now unobtanium because all of the newer heaters use fuel delivery that's similar to what I'm now using.  This is a simple, elegant and cheap way to replace the old dead fuel pump and bring some of those heaters back to life.  There is a bunch of them on eBay all the time and several threads on them on the Samba.  Someone's gonna want something like this.

73's, Jack!  (W4LSU - Louisiana State or Luck of the Draw?)


I'm an electromechanical guy in a solid-state world. I understand what you are doing, and why you are doing it, and would probably have a pretty good idea how to fix it if it broke.

But the "building blocks" were something I never got into, nor were there good classes for basic electronics in the small-town HS I attended.

Regarding understanding thermodynamics, etc.-- those are physical (rather than electronic) principles. I can "see" what's happening in my mind's eye with heat transfer, flame fronts in combustion, the Bernoulli effect (and how it relates to carburetors and exhaust headers), etc.-- but electronics and DDC logic never "clicked" the way that electromechanical stuff did, which hampers me. If I do go to EFI on my T1, I'll definitely have a lot of questions.

As it stands, I'll probably send my (modern) gasoline heater to Danny for some modification (I'd like the controls/safeties to be greatly simplified).

@Stan Galat , the Electro-Mechanical dude!  My very first job "off the farm" was figuring out relay logic for rotary-phone-based telephone switching systems.  That's what's controlling my heater!  Electro-Mechanical Relays are cool!!

So I got my teeny-tiny logic board delivered, along with the MOSFETs I need for it (and 9 others just like it - if you're gonna buy one, you might as well buy ten!)  Those are essentially like adding a relay to your headlights.  Danny P. uses a MOSFET on his board that works just like a relay:  A tiny positive voltage pulse comes from the logic board and goes into one side of the MOSFET to trigger it and it electronically closes, just like a relay.  The beauty is that it can handle more current that the pump needs.  To make it work with my fuel pump we put +12 volts into the hot side of the fuel pump, then connect one side of the MOSFET to the ground side of the pump, and the other side of the MOSFET to ground, just like putting a relay on the ground side of your headlights.  When it is triggered with that tiny voltage pulse it closes the circuit and pulses the pump.  Seriously, that's all there is to it - a basic building block of a relay with no moving parts.

Anyway, I've been slammed with things to do lately and sandwiching in a few bike rides, but I'm trying to get the logic board drilled to accept the MOSFET so I can get it wired in and start to play with it.  I'm looking for an oscilloscope to borrow so I can see what's going on with the waveforms and frequency and that will let me begin to adjust how fast the pulses come and how wide they are, but can work without it if I have to.  @DannyP or @Michael Pickett   Have you played with one of those $20 dollar DIY 'scopes I see on Amazon or a 'scope app for your phone?

Life goes on at the "Five Cent Racing Advanced Heater Labs"

Last edited by Gordon Nichols

@Gordon Nichols, Agreed, MOSFETs are versatile! I had nursed an old tube based analog HP scope from my early twenties until it just couldn't keep up with computer timing speeds. I felt like a super geek when my dear wife bought me a digital USB scope for my laptop. I've had it nearly 10 years and have no complaints. It's been superseded by the manufacturer with this scope:

I like the idea of a phone connected scope but always worry about the rapid changes in connectors for phones.

Monthly update for you erstwhile gas heater aficionados and would-be electronic Geeks!

Things have been a bit busy, lately, what with sitting around watching TV or riding my bike looking at leaves, but I have made some progress on this variable-heat gas heater thing.

First, remember that I'm trying to drive a solenoid fuel pump, similar to a Facet, like this:

Facet Fuel Pump

But a Facet is self-pulsing.  I need something with a range of 150 - 300  pulses per minute or 2.5 - 5 pulses per second.   I already have the pump that can do that, I just need a circuit that can do that, too.

I also need a way of accurately seeing how many pulses are really being produced (it's kinda tough to count them while watching a light or listening to the pump click) so I ended up buying an oscilloscope.  This is an updated version of the USB scope that Mike Pickette's wife bought him (see above post) and you can use it to see waveforms and pulses over time, select the time interval and duration and see it all on a screen.  Pretty cool.

What I bought fits on a computer strip the size of a 4" wooden ruler, it plugs into my Mac for the output screen and the software that runs it and it cost me about $50 bucks.  I've been looking for a decent used 'scope for a few years to use on other projects, so now I'm in Geek Heaven!  In the photo, that is a AAA cell battery on the left, the logic analyzer in the middle and a variable speed pulse generator on the right.  It is amazing how cheap (and small) electronic stuff is these days.


So far, I've been learning about the pulse generator since it came from Amazon/Asia with ZERO DOCUMENTATION!  I've found enough info on the Interweb to figure out how it works, what components do what and I can begin to tailor the pulse speed to what I want. Right now it pulses from about 50 per second to about 5000 per second, but I'll fiddle with a few parts to get me into a range of 150 - 300.  Those parts should be here today and I'll be off and running.   This is almost as easy to change as changing carburetor jets, once you know what's going on and have the right parts.  To do that I needed 2 teeny capacitors but ended up buying a mixed-value-range kit of 180 of them for $7 delivered the next day.  wow.

So that's it.  I'll let you know how this all works ot in the next few days.


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Latest Update:

The damn thing works!  (but then, Danny knew it would, eventually...)  

I needed something to test it with after the circuit mod, so I decided to just use a big honkin' ol' 12V relay so you can hear the pulses.  Remember, I'll be driving a solenoid (click-click-click) fuel pump, so a relay makes a lot of sense - it makes the same sound, at least, sitting on my desk.

So I changed the cap, jury-rigged a MOSFET to drive the relay/pump, hooked up the relay and got this:

THAT, my friends, is a heater fuel pump speed in the ballpark's infield of being "perfect"!  I may have to play with it some more to just use the middle 2/3'rds of the range, but that's an easy change, too.  I also have to decide where/how I'll mount the MOSFET (it's a solid-state relay for the pump) and make that look professional, and then get a nice little box to put it in for under the dash.

Now I'll be able to turn the heat up and down just like Danny and Jack Crosby.  

I love it when something I do actually works the way I want....  


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Last edited by Gordon Nichols

I’m not sure.  Chris believes that carburetors work on the basis of magic/Voodoo, but this heater is a little more like an oil burner so it’s more like “Good Juju”.

Either way, a gas heater is a fascinating little device and it has been fun learning about how they work and improving on it.  Hopefully, this process can be turned into a way to resurrect a bunch of old BN2 or BA4 heaters that are currently sitting idle for lack of a reliable fuel delivery system.

Minuscule progress lately on this - Life keeps getting in the way.    (but then, it took a while to figure out what the heck my-newfangled oscilloscope was telling me.  Maybe if I had paid more attention when my computer techs were showing me stuff....  hmmm?)

A couple more component changes got me to a range of approx. 75 pulses per minute to about 300 per minute.  Not perfect to "idiot-proof" it, but good enough for me.  As a reference, my heater is currently running about 150 pulses per minute and it is warm, but not "hot", so the 300/min will be close to running "too rich" and blowing smoke out the exhaust pipe (yes, the heater has it's own exhaust pipe - Cute little thing, too).

I've also been pouring over Amazon for a little plastic enclosure to put it in (about the size of a pack of cigarettes), a push-button switch to power the whole system on and off (heater and pump) and am currently stumped for a terminal block for the back of the box to attach wires to.  I know what I want, just haven't used the right combo of key words in the search bar to find it - I'll find it yet!

So the next part will be to build the module, mock it up under the dash with some sort of attachment (there is only one place it's gonna fit and be handy) and start making up a wire harness for it.  It would be cool to put the control in a center console like in a modern car, but that ain't gonna happen!  I'm replacing a pulse board that currently sits next to the heater in the car nose with this one that sits under the dash so the wiring harness will be totally different.  Once I decide where to put it I'll mock up a harness, remove it, wrap it in something like shrink wrap for that "professional look" and re-install it.   If all this sounds like a project for over the winter, you're right.  The stuff that's in there now is perfectly fine for now so, like "Mr. Natural", I can keep on driving.

Mr Natural


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  • Mr Natural

Well, after a big post holidays push I've finished the heater controller to provide variable heat output.  Remember that I have a very old BN2 heater which was designed for one heat output level;  Foot-scorching hot but enough to heat an entire VW sedan at 40 below!  I throttled mine back to luke-warm-ish and while it worked OK,  the heat was sometimes anaemic or a bit too much, depending on the outside temperatures.  

I wanted something just like Danny P and Jack Crosby:  Start it up, turn a dash knob to the desired heat output and drive on.  When it gets too hot, turn it down a bit.   Too cold?  Crank it up.

After a little component searching, a few Amazon orders, playing with component values to get it to run at the proper speeds needed by the heater (not go too rich or too lean on the fuel) and chasing a plastic box for friggin WEEKS, then fabbing in the basement, this is what came out.  I used an extra dash knob for the control to match my dash.  This little box is about 5" across and will be stuck to the underside of the (also black) radio with Velcro, making a little center console ahead of the shifter.  The power button is on the right and there is a blue halo around the button that lights up when the unit is turned on.  Pretty cool, huh?


These labels are for the car harness attaching to the box.  They're on the top surface and can't be seen when Velcro'd under the radio.


"What's inside the Box?"  A little pulse generator circuit board and a push-button switch.  That little tab with the hole in it, lower left corner of the circuit board, is an electronic relay controlling the heater fuel pump.


Front view, power on, power light illuminated.  I'm not yet totally sold on that cold-to-hot scale around the knob (it's just there for looks, right now).  I can eliminate the white in the center, but with the red dot on the knob, I don't really think I need a scale and it looks cleaner without it.  "Less is More", right?  Maybe a top center label for "Micro-Scorch 3000" or something.


Now all I need is a couple of warmish days to rip out the old harness/control and install the new one and I'll have "Danny P. quality heat"!

I know that my old designers ( maybe @Michael Pickett, too )  would be peeling their eyebrows off the ceiling over the internal "cabling", but Hey....   It works!  the runs aren't long enough to be dressed!

The birth of another great "Five Cent Racing" product!

If you have (or can find) a BN2 or BN4 heater in good shape, regardless of whether it has a working fuel system, I can spec out a fuel system for you AND tell you how to get it running using one of these controllers and a new fuel delivery system (new fuel pump and trash your old pump and regulator).  Finding the heater and the proper control relays is really the hardest part.  @Matt Berry this is aimed right at'cha, buddy (not that you need a lot of heat in north Florida).  

Something to consider if you want better heat in your Speedster/Spyder/Microbus/Semi-Truck sleeper cab.  


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Last edited by Gordon Nichols

I hate doing wiring harnesses in the car.  I hate it even more when it’s 34° in the garage.  Ever try to use one of those retractable shop lights when it’s cold?  Not only do they not like being pulled out to extend the cord, when you’re done the cord is too stiff to retract!  

So I’ve pulled a bunch (5) of wires of different colors from the heater back to the cockpit, dressed off the controller ends, attached them to the controller, then attached the controller to the underside of the radio with HD Velcro.  I found that the adhesive on the Velcro doesn’t like to stick when it’s cold so I heated things up with a heat gun and “Presto!”   Instant stick.

I’ve dressed the harness back from the controller, through the bulkhead, under the frunk and down to the fuel pump (just inboard of the passenger side front wheel) and connected the fuel pump to the harness, then the cold got to my hands and I had to stop.  Next up, I have to insulate the pump connections and then continue the cable dressing from the pump forward to the heater and make one final solder connection at the heater connector, finish the dressing, put the duct back that I had to move for access and then test it out.  Should be fun!


- pulled a bunch (5) of wires of different colors from the heater back to the cockpit

- dressed off the controller ends, attached them to the controller

- attached the controller to the underside of the radio

- dressed the harness back from the controller, through the bulkhead, under the frunk and down to the fuel pump

- connected the fuel pump to the harness

It's usually at about a point like this that I discover I need a sixth wire.


Last edited by Sacto Mitch

I hear yah, Mitch.

Once I get everything dressed and supported with cable clamps every so many inches and it looks really spiffy and will never flop around, THAT will be when I decide I need another wire for something I never thought of.  It's always that way......

And the more time you take to dress things off and wrap conduit ends with tape to seal everything up, the sooner you'll have to take it all apart to run that one more friggin wire.

Last edited by Gordon Nichols

BTW, if anyone else is interested in taking on a BN1/2/4 heater fuel system upgrade like this, I have documented the heck out of it for myself and would be happy to share that info with anyone.  I'm not too interested in building a bunch of controller boxes but if the demand was there for 4 or so I might be persuaded - I certainly have enough left-over parts!  I'm guessing that a turn-key controller would cost around $60 USD (your cost), the Eberspacher knock-off fuel pumps are another $50-ish USD and the rest of the parts (fuel lines, wiring and such) another $15 or $20 USD.  

OK, @Stan Galat

  I have two versions:  One that is just the controller which expects to get the +12 volts from the heater fuel pump feed and relies on the original heater power switch in the dash.

The other one has a power switch in the controller to power up the heater, and then gets a +12 volt feed for the pump from the heater.  

I'm finalizing a short article to help people decide what they might need to do a conversion on which-ever heater they have:  Early BN2 with a stand-alone, self-actuating pump/regulator or the later BN2 which supplies the pulses to the pump from the heater (and no fuel regulator).

Once I get it done later today I'll shoot you a copy and we can go from there.

BTW:  If your VW Cabbie has a BN4, this thing will work with that, too.

Stay tuned.

Future BN2 MaybeWannahaves:

I've finished the tutorial on whether your BN2 can be resurrected from the trash heap of broken heaters.  It's a little involved - I know....   Once I get to typing it's hard to stop.

If you are truly interested in getting a BN2/BN4 going for your car or VW Bus Camper, PM me and I'll send you a copy and you can decide if this is for YOU.   Otherwise, I won't clutter up the thread with yet another very long post.  

Five Cent Racing's Gas Heater Division

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