Carrier model 398AAZ036060 flame sensor

[medicanic7]

Here are some pictures of the furnace, including closeups of the control board.

[medicanic7]

wiring diagram

[HayZee518]

wiring diagram

I got your wiring diagram. Copied it so I can increase the size of it.
Upon examination of it all I can see is a flame detect relay switch [as they describe it]
I'll have to look further but I think they're using the spark electrode as an ignition device AND a flame sense.
Another thing is, why would the gas valve have a manual pilot knob if the system only comes on when the system creates a spark?
The manual pilot knob must be pressed to open the pilot valve, then turned to ON after the pilot is lit.
So that tells me it is a standing pilot.
Oh yeah, on the controller board, check the fuse. Replace it if its blown. It seems that it is inline with the flame sense relay.

[medicanic7]

After reading many articles on the internet about high efficiency gas furnaces, I was under the impression that the pilot system type is an intermittent one, or an on-demand type. I am not an HVAC technician but I enjoy fixing appliances and other things around my home. I am relatively handy, but furnace problems can be tricky, so I am looking forward to helpful assistance from the experienced people on this great forum, such as yourself.

In the past, I replaced the control circuit board and the blower. That is my experience with furnaces. The circuit board was replaced about four weeks ago, but I will inspect the fuse.

I will wait to see what you determine about the possibility of the spark electrode also doubling as a flame sensor.

[hawkins111]

White Rogers 36E gas valve

You have a White Rogers 36 E gas valve. None of these valves have a standing pilot. Your furnace has either a Proven pilot or Cycle Pilot system. Due to the type valve you have I think you have a bad gas valve or a circuit board problem. If you have trouble getting to the bottom of this call a good gas tech and he could troubleshoot this quickly. I could not attach the PDF file as it's too big. This is the link to the file:

http://www.emersonclimate.com/Documents/White-Rodgers/sell_sheets/R-4060B_36E_36F_Gas_Brochure.pdf

Tom

[HayZee518]

intermittent pilot

went to two sites having to do with intermittent pilot.
both places show a combination spark igniter along with the flame rod sense on the same electrode.
the main gas valve and the pilot gas valve connect to this spark module through three terminals
it also shows a prepurge fan and inducer fan control.
the spark igniter is separate from the main control board.
the 36E Hawkins mentions looks like the valve.
se if you can find the spare parts section and see what they recommend for a spark module.
I recall installing something like this on a WASCO electric commercial dryer.

[medicanic7]

gas valve

Tom,

Thank you for determining the make and type of the gas valve. I will reinspect the control board for the ignition system and the one I recently replaced for damage.

[medicanic7]

intermittent pilot

HayZee518,

Thank you for your continued research into this problem. I will inspect the ignition control board, and parts section for a suitable spark electrode/flame sensor. Also, I will learn more about the valves you mentioned and inspect them. I reviewed the wiring diagram and noticed that one description states the ignition burner assembly is somehow also the flame sensor. I don't know exactly what part senses the flame, but you suggested it was possibly the electrode, but you also suggested that I look at the parts section for further clarification. I will do all of this.

[hawkins111]

740A Electronic Ignition Switch

Bryant - Carrier 3 Wire Pilot Safety Switch - LH680005

	(0 reviews)

Carrier, Bryant, Day & Night, Payne Furnaces use this 3-wire Pilot

740A Electronic Ignition Switch with built-in Safety

Style/Model: 740A

Orifice Size : .017

Differential expansion pilot equipped w/ a 3 lead SPDT switch for use w/ a hot suface Ignitor or spark Ignition
(YELLOW, WHITE, GREEN WIRES WITH MOLEX PLUG ADAPTER)

Replaces Pilot Burner Part Numbers

535740A 535-740A LH680005 1830-620 535-740 535-740A LH680005 P671-1406 CARL38999 CAR1830620 740A 1830-620 535740A

The pilot does have a relay, it is heat activated (warp bar), it is in the bottom of the three-wire pilot module.

The sparker is just a sparker the heat activated relay is how it "senses" flame. Yellow is the common number 2/3 on gas valve.

Green (number 5 on gas valve) open the pilot valve when the pilot module is cold.

White opens the (number 1 on the gas valve) main valve when the module heats up. The warp bar is what makes the switch.

[HayZee518]

flame sense

Hawkins, I think I already brought out that combination spark unit and flame switch in one of my page one posts.

[medicanic7]

740A pilot burner

Tom,
Thank you for the explanation about how the flame sensing part of the pilot burner works. This is good information. Yesterday, I reviewed the PDF concerning the gas valve. All the detail is great.

[medicanic7]

Much thanks

HayZee518 and hawkins111 have supplied me with sufficient and detailed information to allow me to proceed with confidence to replace the pilot burner or gas valve or, possibly, both. This forum is tremendous. My brother was also impressed with the information given to me. I am glad I registered.

[eriksat1]

I have the same furnace Model 398AAZ036060 but propane gas, a sticker says it has already been modified for propane, will this still be the correct part LH680005 pilot safety switch?
What my furnace is doing I turn up thermostat hear a fan run, then a click and the pilot lights I can see it through the little window, the pilot stays lit for about a minute then clicks off, the main burner never lights, I don't hear a click or anything for the gas to the main burner to come on, and after about a minute the pilot shuts off. Is this pilot safety switch my best bet at fixing it, or could it be something else?

[KDGrayson]

Hello forum. I have a Carrier upflow gas furnace, model 398AAZ036060. If this furnace has a flame sensor, can someone please tell me where it is located? I searched the burner compartment but only see the pilot burner and spark electrode assembly near the burners. Thank you for your assistance.

That unit uses a 3 wire pilot switch and a common failure with these units, there is no flame sensor, the pilot switch has 3 wires 1 is cold, 1 is hot and the 3rd is the hot leg feeding in to it, in cold position its closed to the ignition, in hot to the gas valve.
replace the Carrier 3 wire pilot switch.

[eriksat1]

That unit uses a 3 wire pilot switch and a common failure with these units, there is no flame sensor, the pilot switch has 3 wires 1 is cold, 1 is hot and the 3rd is the hot leg feeding in to it, in cold position its closed to the ignition, in hot to the gas valve. replace the Carrier 3 wire pilot switch.

I replaced the pilot switch and all is well, thanks.