[SkyKing]

I don't have the manual from Cessna yet, but it's "on order"... I'm also awaiting arrival of the Janitrol B2030 Series Heater Service and Overhaul Manual from Kelly Aerospace.

John... Do you know when the last pressure decay test was run on your Janitrol? There are two AD notes on the heater that affect the 42D36 combustion air pressure switch that's mounted on the upper forward part of the heater unit, as well as the combustion tube itself and the fuel regulator shut off valve. The applicable AD notes include 96-20-7 pertaining to the integrity of the combustion tube (a flame erosion problem) and the combustion air pressure switch, and 2002-08-01 pertaining to the JanAero Series 14D11-7.5 fuel regulator and shutoff valve.

The old style 42D36 combustion air pressure switch is generally the culprit and will keep the heater from operating and it is primarily through shops messing with the switch through over adjustment and consequent de-coupling of the pressure sensing spring that's inside the unit which will render the switch inoperative and your heater ka-put. What generally happens is, you will hear the fuel pump and regulator clicking away, the blower on full high, and the heater either trying to intermittantly light-off or not at all. After a light-off attempt and you shut things off, you should see some fuel dripping from the overflow drain tube which comes through the left lower front engine cowl.

Of course, you could have other problems, like the thermostat switch as the base of the pilot's rudder pedals, or if you don't have the levers in the right position and there isn't sufficient air flow through the heater, this too will cause the combustion air switch to stop the process and the heater will flame-out. Very seldom is the 39D18 spark plug a problem. The spark plug is $80 bucks.

You'll probably have to have the unit checked by a qualified mechanic that is FAMILIAR with the Janitrol B2030 series Heaters as installed on the 337's and who has a copy of the service and overhaul manual (P/N 24E25-1). The AD note on the combustion air switch and combustion tube has to be done every 24-months or 100 heater hours TIS (Time in Service), whichever occurs first. This will still be the case after you replace the older problem- causing 42D36 combustion air pressure switch with the newer 94E42 switch. They're about $160 bucks.

BTW, since the Janitrol heater gets its fuel supply from the left tank, make sure the overhead console fuel shutoff valve is in the green or yellow crossfeed position.

In the meantime, if you want to check the combustion air switch for proper continuity, with everything shut off, you can disconnect the two leads going to the top of the switch-- it's a round thing with a flat top and a black phenolic area on top with two screw terminals that sits on top of a short standpipe at the forward part of the heater, adjacent to the spark-plug and ahead of the main terminal block. After you take the two leads off, connect an ohmmeter or continuity tester across the switch terminals. If the unit is good, you should have an 'open' indication. If you get a 'closed' indication, i.e., a short between the terminals, then you have a bad combusiton air pressure switch.

Hope this helps.

SkyKing