Hello everyone, I have been reading through these forums for hours starting yesterday.

Let me start with the specs, then explain with what I have done thus far.

Comfort Maker RPJ II, it also says arcoaire on the front.
Control Module is White Rodgers 50a52-111
3 Burners
Electric ignitor on middle burner with flame sensor below the ignitor
I dont have the PN for flame sensor on hand, I had it out yesterday and it is a white rodgers with the glass window, I want to say a radiant type.
The thermostat being used is a Ebay touchscreen knockoff, has worked well the last 3-4 years, but I ordered a honeywell 5-1-1 to replace it just in case.

So now onto the symptoms:

#1 house is cold = unhappy wife
#2 Furnace not running
#3 When I turn off furnace at switch and turn back on the furnace will attempt to ignite
---1 Exhaust fan runs for about 30 seconds
---2 ignitor will glow but no ignition,
---3 ignitor will unglow and exhaust fan will run another 30 seconds
---4 ignitor will glow WITH ignition
---5 Furnace will operate for 2-5 minutes before shutting off below the thermostat desired temp.

** After Cleaning Window on Fire sensor, this is current operation**

#3 When I turn off furnace at switch and turn back on the furnace will attempt to ignite
---1 Exhaust fan runs for about 30 seconds
---2 ignitor will glow WITH ignition,
---3 Furnace will operate for 2-5 minutes before shutting off below the thermostat desired temp.
---4 Furnace will restart itself and attempt 2 trys at liting funrace (this is what control SHOULD do)
---5 ignitor will glow but no ignition
---6 ignitor will unglow and exhaust fan will run another 30 seconds
---7 ignitor will glow but no ignition
---8 ignitor will unglow and exhaust fan will run another 30 seconds
---9 Furnace shuts off... (According to the sticker on module, it will do 1 restart with 2 attempts then lockout for 3 hours)





What I did yesterday was take out the flame sensor, the small black box with glass window. I cleaned the window and popped off the metal and tested the operation of the switch. With my meter hooked up it had continuity between one terminal and the next, and when the switch was activated it became an open. The other terminal of the switch worked opposite. Indicating that the switch logic is working correctly (unless of course it heating up incorrectly and making contact when it shouldn't be)

I also ran resistance on the ignitor, it was in the recommended window from what I read yesterday.

The control module that my furnace has does not have an LED so blinking diagnostics to help me on this one.

Thats all I can think of for now, open to any suggestions. Can also take pictures of things if that will help.

I also called the local repairman this morning listed on the front of my furnace "for service" but I got a voicemail. Dont know when I will hear back from him, might not be till monday. And I am pretty handy with a meter and tools, so I would like to fix it myself if possible.

Thanks in Advance

 

Photos:

 

Well as soon as I got a hold of the local HVAC guy the furnace decided to fix its self... darn electrical gremlins...

Actually what part of it might be is that yesterday when I was working on it I went to store and picked up a new filter, the new filter was a the wrong size and I couldnt put the cover over top it on the intake ducting. Today when it started working the only thing different was I put in the correct size filter. I wonder if it has to with pulling the air through the ducting correctly?

I will give it a few days to see if it settles out and keeps working or if its a temp fluke and stops working. Maybe a pressure differential in intake are from the intake ducting?

Either way, will keep posted on here.

 

stopped working again, I called the HVAC guy again, and he confirmed it was the part I thought it was.

After doing some research I determined that it is a 3 pin radiant heat sensor, that they no longer make... My options are a $500 retrofit kit or a new furnace.... neither of those options are budget appealing.

They do make a 2 pin radiant heat sensor for gas dryers that looks like it should work perfect. I made a diagram to show how i think I could wire it up. Let me know if this looks correct.

 

hey, i have a similar problem. furnace will ignite, light, exhaust fan runs, and flames go full force. but it will run for a while like this, but the blower fan never starts. would this be the same problem with the 3 wire sensor?
thanks

 

Caribeso:
While the furnace is running measure voltage between the fan heating speed terminal & neutral. At some point before the furnace shuts down you should get 120 volts AC. If you do & the fan does not come on, I'd suspect a bad fan motor.

 

Yotato. Did you get the 2 pin radiant sensor to work on your furnace? I am having the same problem with my furnace.

 

YotaToy - My unit appears identical to yours with the exception of 4 burners instead of 3. I have been following your diagnostic path closely. ((What drives me NUTS is that when my upstairs HVAC took a dump in September that I did not grab either the 100% functional control module or flame sensor. ARRRGH.))

My unit is not starting reliably with the T-stat. I need to jump T-stat terminals or cycle the contact switch on the cover in order to get heat.

My flame sensor was not dirty but the glass was cracked and corner had fallen into the opening. I removed glass, cleaned it, and reversed it in the unit so that the opening had a complete and clean piece of glass. I did clean the switch contacts with emery paper. After reassembly and install I was **not** able to get gas valve to click/click/click (gas shuts off flame dies) when I jiggled the leads to the flame sensor. After cleaning and assembly....is the position of the ignitor ...."closer" to the flame sensor glass..? Probably, maybe 1/4" or so.

Did you see the other posts about shimming the connector that goes into the top if the gas valve...? Removed the resistor pack on top of the gas valve and cleaned the 4 long (thin) contacts with emery paper. Took out the 2 screws and removed the resistor pack. On the bottom of the resistor pack I did not see any weak solder nor corrosion. Reinstalled. I shimmed some tension between the plug and the valve body using a piece from leader of thin cable tie.

What I learned today - if your pressure switch (silver disk upper right of foto) loses pressures and opens the circuit, your gas will shut off and flame will be lost. If your exhaust motor is spinning and the unit is trying to light, briding (or opening) the contacts on the pressure switch would be an easy test. Not sure if switch is normally open (NO) or normally closed (NC).

 

Since my repairs mentioned in my prior post the furnace has responded to a few dozen calls for heat without the need to open/close the cover door or to turn the thermostat from Heat--OFF---Heat. Furnace has been cycling normally.
Needless to say......fingers crossed.

I have not been able to find anybody who has stock of the (obsolete, discontinued) 3 wire radiant heat sensor, nor any product information
about this system.

 

Before replacing parts this is a common problem with a simple fix. The wiring harness connection on top of the gas valve (red arrow pointing to it in picture) vibrates loose. If you tighten it with a wire tie it can solve the problem. I did this a few times to get it to work (would light, run for a few minutes, then would shut off). After the last time I worked a pin loose on the black piece it plugged into. This time the gas would not come on, the valve was not opening. After soldering all of the pins to make sure they were tight on the little circuit board and re-tightening the plug it is now working again.

 

I am trying to find out what the name of a part actually is and where I can buy it. On the last picture of this thread is a part in the upper most right corner. It is the round piece with 2 blue wires coming from it. It is also being held in place with a rectangle bracket. This part is not working and I have gone to 3 local part stores with no luck. I have been searching the internet for 3 weeks when I found your group. Please can someone help me? I have been trying to fix for 4 weeks and I have run out of parts to test or replace. I have been talked down to by all the men I have encountered, telling me call an HVAC Tech. I cannot afford their hourly rates, so your group is my last hope. Thank you

 

That is a vacuum switch. It senses when the inducer motor is running properly and then allows the igniter to start. How have you tested it? If you have a test meter, remove the connector and measure ohms across the contacts of the switch. They should be open - no resistance. Then send a call for heat to the furnace. The inducer motor should start and the contacts on the switch should close - and your meter should show a short circuit condition.

If that happens, the vacuum switch is okay. If not, check the rubber hose between the inducer and the vacuum switch. Pull the hose from the blower and clean the blower housing nipple with a stiff pipe cleaner or a close fitting drill bit (by hand). Also, if you suck gently on the hose, you may hear the switch click and the meter to show a closed circuit. That would mean the switch is good and just not getting enough vacuum pull from the blower.

By the way, welcome to the forums.

 

Had problems on and off with the RPJII since we moved into the new house 20 years ago. The problems I had were as follows:

1) The PCB was damaged upon installation or assembly at the factory. The PCB had a hairline crack that made it intermittent. I soldered jumper wires across several traces to fix that. This I suspect was one of the unusual failures. I think it was the PCB that was in the gas valve that the relay plugged into. It could have been the controller though. It occurred 20 years ago.
2) The nipple rusted/corroded off the furnace where the rubber hose plugs into to sense the exhaust motor is running. Had to dig it out of the hose. Fortunately there was enough end left to plug it on.
3) door switch was broken.
4) Hot surface igniter went bad.
5) Flame sensor needed cleaning with steel wool a few times.

The sequence these furnaces run is as follows: Thermostat calls for heat (simple closed switch), exhaust motor turns on, hot surface ignitor glows red, gas comes on and flame lights, blower turns on. There are two thermistors (temperature sensor switches) that sense the correct temperatures in two areas, plus the vacuum switch the senses the exhaust motor. There is also a door switch for the panel below that checks that the door is in place so air is drawn from the proper place. The unit I have has fault LEDs to help with diagnosis.

Overall it has been a good furnace though!

 

i finally got my furnace working, it was not the fan b/c it ran fine when fan switch was set to ON
i tend to agree with the loose connections on the circuit board, i tightened everything up and it works fine.

does anybody know the CFM for this model? [GNI045A012AIN]
also, is it possible to run this unit horizontally, and if so, are there any modifications necessary?

thanks

 

Too many hijacks here.. Closed. Please start a new thread...

Thanks....