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  Baron B55 S50/D83A28 Janitrol Heater Mysteries Revealed




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See pictures below of duct areas that get hot and take a beating in the heating system.




These are pics of a C&D Associates find that was lurking under the floorboards of a Baron. Well this explains why there was no heat getting to the rear of the airplane. Can you say "thorough annual" where the floorboards are lifted to take a peek at things?



Here are more pics of distorted plastic duct work that could be lurking under your floorboards




The ducts are thermoformed plastic.  They soften and melt when they get hot.  This owner repaired the bad joints in his Baron with fiberglass and reports not having any problems since.



Below is the fix C&D employed in straightening out the mess:




Below you will see pics of all the exciting pieces that go into a Janitrol Model S50/D83A28 heater that was factory equipment for the early Baron and Travel Air (probably up to 1973 vintage, but check your parts catalog to be sure).


Section 10 of the Beechcraft Maintenance Manual also has some good guidance for Janitrol heater maintenance as well and you should follow those guidelines. Here is some source material:


The Baron Heater Wiring Diagrams Extract is HERE


A Travel Air Heater Wiring Diagram Extract for TD-534 thru TD-637 is HERE


The Janitrol Parts Catalog & Illustration for the D83A28 is HERE


The Janitrol S-Series Heater Maintenance Manual is HERE


CA476284E-1 Janitrol Heater Fuel Pump Replacement Install Guide is HERE


The Janitrol Heater Overhaul & Maintenance Manual 1981 is HERE


Hartzell Heater Parts Catalog is HERE


AMT Janitrol Nose Heater Article HERE


Carbon Monoxide Myth from Janitrol Style Heaters Article HERE



Nexus Climate Systems in Holland, MI 888-701-Four-Seven-Six-Seven is a source of parts and service for Janitrol Heaters. Here is a recommended list of parts from former C&D owner, Bill Sandman, to get the S-50 heater back into winter fighting shape:

• G36A47: Nozzle, fuel 2.00 GPH
• 54A35: Spark Plug (gap 0.312 to 0.250)
• 51A66: Nozzle Holder Gasket
• 52A02: Head Gasket
• A35A71: Rope Gasket (8”X3/8” for S-50)
• 51A05: Serviceable Ground Electrode 
• The package also included a foot of 7mm lead material (to overhaul the ignition lead).


1/29/2013 NEWS FLASH from C&D:


C&D Associates Inc., manufacturer of the world’s safest and most reliable aircraft combustion heaters, is proud to announce "A.D. FREE" overhauls of both JANITROL and SOUTH WIND/STEWART WARNER heaters.


As always, C&D’s Dash one (-1) series heater remains A.D. free (After 16 years and 3500 plus units in service with zero malfunction defect reports under our belt.) Confidence in product safety now allows us to offer the C&D Durakoat™ combustion chamber as a cost effective alternate means of compliance to Airworthiness Directive(s) AD2004-21-05 (imposed on Janitrol B-Series previously AD96-20-07, previously AD82-07-03,) and AD81-09-09 (for South Wind/Stewart Warner.) These A.D.’s will no longer apply to units undergoing complete zero-time overhaul by C&D Associates Inc. Resulting in better-than-factory-new condition, these overhauls will utilize C&D’s Durakoat™ combustion tube as well as multiple updates necessary for longevity and safe operation.


Thanks to the most knowledgeable staff in the industry and an extraordinary record of safety, C&D Associates Inc. continues to set the bar on aircraft environmental systems. In an effort to promote aviation safety in this regard, C&D will offer the complete overhaul at a cost similar to the purchase price of the combustion tube itself.

Here is what C&D has to say about Janitrol nozzles and spark Plugs:

Its really tough to clean a heater fuel nozzle. Plus if the spray pattern isn't verified out of the heater it's hard to tell what its doing IN the heater. A great way to tell if you have a nozzle problem is to hold a piece of metal flat but loosely against the exhaust while its burning. If the burn pushes smoothly against the metal then your spray pattern is probably OK. If it chug's or pulsates against the metal as it burns then a NEW nozzle (or overhaul) is needed.

Also, cleaning a plug with a rag and maybe a mild 3M pad is fine. If the plug was sandblasted its basically trash. That glazing on the ceramic is vital for proper ignition. And just as important as a clean (New) plug is on a Janitrol, a properly set gap is just as important. Verify its 0.156" -0.188".


Call today for a quote: 855-234-3287! Availability typically runs 5-7 days (AOG, 24-hours.)


C&D Associates Inc. Your complete source for A.D. free aircraft combustion heater products and parts.


855-CD-HEATS (234-3287)

PS: C&D Associates is now part of the Hartzell Family of companies.


The good news is that they make these parts available, the bad news is that they are horrendously expensive! When was the last time you bought a spark plug for $100? (You fine wire guys sit down and shut up........LOL). But seriously, the plugs in these units give quite a long service life with a little care and cleaning.


If an $8,000 new C&D Heater (by the way - they have AD Free models available for Beechcraft) is not in the cards for you (like the one pictured below), then read on and see the ideas for getting your Janitrol back in action!



Here is another resource for Janitrol Service and Parts: Harold Haskins

116 Race Track Rd.

Dothan, AL



And yet another source for Janitrol Parts is Cumberland Aero. Baron owner Pete R. reports Cumberland had the best price for the spark plug.


Cumberland Aero

121 Boss Lane - Boss Airport
Bronston, Kentucky 42518
1-800-524-6319 or 606-561-5260


And yet another source for Janitrol Parts & Service is Aircraft Heating & Electrical. Baron owner Pete R. reports that he had an AOG situation when his heater igniter went TU in the winter of 2016. John at Aircraft Heating received in his unit and diagnosed and repaired it in the same day, getting his bird back into winter service the next day. Pete reports the repair at about $300, which is about the cost of a serviceable unit off eBay without any warranty. The typical Janitrol igniter PN 11C30-1, is pictured below. This is the unit that provides the electrical energy that goes down through the ignition wire that connects to the spark plug whose spark ignites the fuel in the heater can.




Despite the horrific expense of these parts, this model of Janitrol seems like a pretty robust design and with regular bi-annual maintenance of the spark plug, electrode and your original nozzle, things should be toasty warm, but that's just my humble opinion.

CSOBeech Bonus Find: Heater Fuel Pump Filter Kits are PN: FEP 42370 available for half the price of HBC at around $7 from Aircraft Spruce HERE. Consists of a new filter screen and a new gasket. Better to change those while you're in there as they are often neglected for decades



Here is a picture of the old style filter for the Facet pumps:



Looks like these Baron/Janitrol heater fuel pumps (2) were/are Facet Cylindrical 24V Solid State Pumps. Later model B55s are reported to have only one pump.





Check out the Facet pump spec sheets HERE





1. I learned that in addition to a good clean nozzle, spark plug and electrode, a very important piece of the heater equation is the spark plug wire .


I found severe arcing through cracked wire insulation in the ends that was contributing to poor/intermittent heater performance. Gee, it was only a 40 year old wire! So, make a note to self, change out that spark plug wire if it is decades old.


My IA had some solid core wire and ceramic insulating ends, however, C&D has a repair kit consisting of fresh wire and connector ends that will enable you to make up a new wire to fit inside your existing braided connector. Use some safety wire and a liberal dose of DC-4



to pull your new spark plug wire through the semi-rigid braided connector.


2. I also tested the overheat circuit of my S50 heater to be sure that the unit shut down as designed at the 300F plenum temperature. The overheat thermostatic switch resides in the furthest aft position of the heater, just aft of the heater combustion chamber.  (PS: This picture was taken in 2004 to point out to the selling broker that the overheat switch was not connected to ground)



What I did to check mine was run my heater at highest heat setting in my hangar with about +1C ambient air temperature. I used an infrared pyrometer to measure the plenum temperatures at the rear of the heater and in the plenum duct on the co-pilot side where the thermostatic switch is located.


I found that under these conditions my overheat switch functioned and did it's job of blowing the 5 amp fuse in the circuit. My IR pyrometer recorded a plenum duct temp of about 235F downstream of the location of the overheat switch. The overheat switch is fed from the same power source as feeds the ignition coil, fuel pumps and fuel solenoid valve, so when the other side of the overheat switch goes to ground, my heater no longer has fuel or ignition.


We made an adjustment in the thermostatic switch cable:



so that the highest heat setting makes for a lower plenum temperature (about 210F) and does not blow the fuse.


My subsequent trip north at 11,000' with an OAT of -8C allowed for low heat settings to make the cabin quite comfortable. I'm expecting that when we get colder OAT temps, I'll have enough heat setting to be able to be comfortable.



If you live or travel to frozen tundra territory in your Baron or Travel Air, things get mighty uncomfortable in a hurry in  the winter temps that can be experienced up there at altitude, so make this a definite checklist item for your annuals or check it every two years.


NOTE: All of the below operations were done under appropriate A&P supervision, so get yourself some supervision or help your A&P/IA with a link to this page so that they can be briefed on what to expect in there if they have never done these heater maintenance operations.



25 November 2009 NEWS FLASH: GOOD NEWS, Mark M. @ Dodson came to my rescue with a complete low-time (yeah they included the Hobbs showing 43 hours) S50 Heater for about the same cost as some of these guys get for a new Ignition coil/vibrator combo! If you have heater woes give Dodson in Kansas a call (785) 878-4000 and tell them CSOBeech sent you.








This is the heater head where all the business parts are fitted. At 12 o'clock is the $100 Spark Plug


. At the 6 o'clock position is the electrode, the spark plug and electrode meet in the center


 with a gap for spark arcing. At the center position is the fuel spray nozzle which gives a fine


 spray of fuel to be lit off by the spark.



While we are talking about spark plugs in these heaters, check out what Bill Sandmann of C&D Associates found when he was troubleshooting a customer's "no-heat" squawk!




Yup.....the electrode is completely gone!


Below are a few more gems for "intermittent" or no heat out of your Janitrol.



These are some of the surprises that can be found when Janitrol heaters are not regularly maintained and inspected.





This is the heater data plate, on the right side (co-pilot side) of the unit. 





This is the heater blower that lives under the nose cone in front of the heater can. The first picture is

the front end and the one on the right is the rear of the blower assembly. This blower assembly hangs

in the front by some screws and the rear by a clamping strap to the front end of the heater. I made

sure the front end was clear of obstructions to flow air. On the ground the blower runs (and only ONE

of the fuel pumps fuels the heater), when the gear is in the wells the blower does NOT run (BOTH fuel

pumps are actuated with gear in the wells), you are running off ram air coming into the nose cone. An

up-limit switch on the gear transmission switch assembly contains a BZ-3YT double contact switch

which allows power to flow to blower motor when the gear is down. When the gear is up the switch

contacts close on the other set and allow power to flow to the 2nd fuel pump. If your blower motor

decides to quit running on the ground, check for power at the motor connection in the nose cone and

if there is no power there, it is likely your BZ-3YT (SPDT) switch may have failed. Since the Common

terminal is not used, the BZ-3AT might also be considered (with A&P approval) for this task as well.

Need more landing gear gouge details? Check out this CSOBeech page HERE.

Support Buy the BZ-3YT / MS25383-1 Micro switch below:

BUY NOS BZ-3YT / MS25383-1 Below

Shipping Option

There is a shutter mechanism  on the blower, this is called the "Iris Valve", you have a cabin air handle

on the pilot side at the lower part of the instrument panel, when you pull this handle you pull the

shutters closed on the Iris Valve and LESS air comes in the cabin firewall vents. When you pull this all

the way closed a micro switch closes and shuts the heater down because you are not flowing any air

and that would be very bad to have all that heat happening and no air coming across the heater can

(DUH!) Cleaning the iris vanes is a good idea to insure smooth operation. Many people suggest

pulling the Iris halfway to get a warmer air temp into the cabin. I've not tried this technique as I'm a big

fan (pun intended) of flowing as much air over that hot can as possible. You're the PIC, you decide!






Blower motor data plate information.






Dirty electrode removal.







Bead blasted electrode cleaned up.






This is the area under the heater showing the blower motor strap clamp to the front of the heater 


assembly. The picture on the right shows the Iris Valve actuating mechanism and the 


micro switch and coil/ignition vibrator location (coil/vibrator removed). I lube this area of the


 mechanism regularly with CorrosionX).








This is the area that must be disassembled to remove the nozzle plumbing. This is directly behind


 the coil and ignition vibrator (torpedo looking thing) under the nose shelf. The coil/ignition unit is


 held on by two band clamps with phillips screws. See the screw holes in the picture. The


 stainless enclosure has a little cover on it with two long screws to the front and two short ones 


to the rear. The two long ones reach all the way down to the nozzle plumbing fixture. The two 


short ones hold the cover to the stainless enclosure. There are two screws in the base of the 


enclosure that are securing the nozzle plumbing to the outside of the heater can structure. I 


left those in place for rigidity. I then removed the fuel line fitting going to the 90 degree elbow.


While holding the rear of the nozzle plumbing, I fit a small wrench in there to loosen the 90 degree 


fuel fitting. After I removed the 90 degree fitting, I removed the last two screws to the rear of the


nozzle plumbing fixture and the whole piece of plumbing to the nozzle was then loose.








I removed the nozzle with a 5/8" socket.




Here are the dirty and nasty things that were found in my neglected heater nozzle (your humble


 CSOB is guilty of 5 years of neglect and the CSOB before me is guilty of a number of years as 


well). This definitely impeded proper fuel flow and spray pattern atomization for my heater 










New Replacement Nozzle Available

Nozzle Shipping Options

Here are thoughts from frozen tundra Baron owner, Richard S. who obviously knows how important keeping his heater in shape is to flight in winter months:


When you unscrew the filter from the nozzle, you'll might find some junk inside the nozzle, too. There are a couple of little parts inside it that control the flow and the spray pattern. They unscrew from inside the nozzle. The C&D folks said that when those tiny passages inside get disrupted, the flow reduces, the fuel spray pattern distorts and the fuel won't light off, even faced with the fireworks from a nice new spark plug.

Cleaning the nozzle is not in the annual inspection list, but it's shown in the heater maintenance section of the shop manual. It is a pain to get it out of the heater, but the C&D folks recommended doing it every couple years to make sure the nozzle is clean. They said it's the number one cause of intermittent heat. So, I just plan to do it every other year, taking the nozzle apart and ultrasonic cleaning it and the tiny bits inside it. The heater is pretty much a go/no-go item up here in the frozen tundra.

There is a conventional sump drain filter in the fuel line downstream from the heater fuel pumps. It's just like the main sump drain in a Bo. It's supposed to be sumped before flight and disassembled and cleaned every annual. Apparently it can't catch everything.

Here's the shop manual text:

Cleaning the Spray Nozzle

1. Disassemble the spray nozzle by unscrewing the fuel strainer and two piece core from the nozzle body.

2. Clean the parts in Stoddard solvent.

3. If soaking fails to thoroughly clean the parts, scrub them with a soft, non-metallic brush.

4. The grooves in the core and orifice in body, may be cleaned with a soft pointed piece of wood.

Stay warm!







Of course, you can clean the old nozzle and make it serviceable again (the Beechcraft


Maintenance manual approves this), however, I used my Emergency Revocation powers to


revoke my CSOB card when I was buying the spark plug and purchased a new nozzle as well.






Pictured above is the Thermostatic Limit Switch assembly. It is PN: G714127. It is located just above the

co-pilot's rudder pedals and just under the firewall air vent where you can hardly reach it (big surprise



Here are additional pictures of the thermostat assembly.





The cable determines the set point at  which the heater will cycle on and off. The little cam with the

white plastic molded lip is connected to a coil that sits in the heater plenum and turns as the plenum

heats up and cool down, thereby actuating the micro switch. The micro switch in turn passes power to

the fuel solenoid valve (the solenoid shut valve is just downstream of the fuel pumps in the nose gear

well) which opens to allow fuel flow to the heater in the presence of 24 volts.


This micro switch PN is no longer produced, so if you have a failure here you may have to search out

some alternatives. Here is what Beech lister and B55 Baron owner Richard S. found that might be able

to be modified to work:



The above is: WZ-2RW822-A2. Available from Mouser HERE The pdf Data Sheet is HERE


Always be sure any part substitution is approved by your A&P/IA for return to service. A review of  the AC 23-27 Parts and Materials Substitution Guidelines could be worthwhile.



Below is a picture of the hideous location of the 5 amp overtemp glass fuse holder and the spare. This is the fuse that will blow if you get really enthusiastic about having heat with an S50 that has not had the thermostat adjusted so that it WON'T overtemp! You will need to be a very agile person, a small child or have a chiropractor at the ready to reach this fuse. The best way to describe the location would be to say that it is located just above the firewall opening where the big battery bus cables enter the cabin.





DIY Janitrol Pressure Decay Test Tools


Contributed by Baron B55 owner, Jon B, below is his Janitrol pressure decay DIY tool set up. Easy to duplicate, he sourced the plugs from a swimming pool supplies store. Here is his narrative:


"My heater is the "S" series D83-A28 (S-50) that is not affected by the A.D. I like to check the integrity of the combustion tube every annual anyway. This model heater was used on the earlier Barons, you may not have this same model, so my PDT setup may not work, or you might have to improvise some additional components.  


The setup on mine is simple, you can do it on the airplane, you just attach your compressed air source to the fuel drain tube and a pressure gauge with appropriate plumbing in place of the fuel inlet line. Pressurize to 6 PSI and time the leak down to 1 PSI. YMMV..."








Baron Owner, IA & ABS Member Stuart Spindel Janitrol Heater Narrative


Old style Janitrol heaters (S50) were used thru 1973 models. Very good and robust.


Downside was the rather expensive ignition unit. Coils still available, vibrator still available, now solid state.


Back in the fifties, when the gasoline powered twins were big Commanders, Twin Bonanzas, Queen Airs, Beech 18, Lockheed Lodestars and such, the Janitrol heaters were popular. The smaller twins got Southwind heaters, but Beech elected to use the Janitrol, but one with a smaller fuel nozzle that was essentially a derated heater.


The newer heaters have several advantages over the older models, but robust cans (combustion tubes) is not one of them.


Yes, there is no AD on the older heaters, but somewhere between an over cautious two-year check and never checking at all, is a reasonable interval. Four years seems about right.


The pressure of the outside air that surrounds the tube as it flows around the heat exchanger remains higher than the pressure of the burning fuel-air mixture. Cracks will let vent air into the combustion tube, not the other way around.





Your ignition coil/vibrator is TU?


Here is a pirep from Baron owner Joe B.:


The culprit was the ignition coil, PN 11C30-1. It was not very expensive by aviation standards. I


shipped the old coil and wire to Aircraft Heating and Electrical, 1635 Beltline Road


in Redding, CA 96003 916-246-HEAT (4328).


They tested my old coil on the bench and it would work, then shut down when it got hot. After it


cooled off, it would begin working again. The coil is supposed to fire all the time, even when the


thermostat has cut off heater. They shipped me a new coil and wire. Problem was solved.







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