My problem is with a RA 80+ Upflow/Horizontal furnace (G6RA), installed about 14 years ago. It has worked great for 7 years, until yesterday. The burner will not ignite. The sequence that occurs is: 1) inducer comes on triggered by thermostat, and continues to run throughout the following sequence; 2) the board's red light comes on, no yellow light; 3) a small click noise happens; 4) the igniter glows hot for 30 seconds or so; 5) no gas emits; 6) as the igniter begins to fade, a clunk noise sounds from and is felt at the gas valve; 7) about 30 seconds later the red light flashes three times in a row, three consecutive times (pressure switch stuck closed); 8) the system goes quiet for a few seconds, with no inducer fan running, then the sequence restarts and repeats without stopping.

I have checked the pressure switch and the contacts inside move with slight vacuum. The rubber tube is good with no holes. I also jumped the orange wires leading to the pressure switch, after the inducer fan comes on. The furnace still will not fire.

One other twist: yesterday, a few times the sequence did not occur as above. Instead, something (the transformer maybe?) would hum, without the inducer fan running, nor did anything else in the furnace run.

Thank you for your help!

 

You may have a bad control board. Have you ensured there is gas present to the gas valve? Have measured ac voltages to components?

 

Hi hvactechfw. Thank you for your speedy reply. I don't have tech equipment and don't know where or how to test the control board. I have a small Electro-tec analog multimeter, a tool box, and elbow grease. Any suggestions?

 

http://www.nordyne.com/Literature/708291b.pdf

It does sound like a faulty control board.

Measure fore 24VAC to the gas valve after the ignitor glows.

 

Thanks, Houston204!

I noticed some new info in the manual you linked. The manual's trouble code for 3 red flashes is "Pressure switch is closed with inducer off." But the schematic on the inside of my furnace's cover reads only "Pressure switch is closed." It doesn't say anything about being closed with inducer off. I don't know if I'm misinterpreting this, but it sounds to me like the inducer staying on, which it does, could be another symptom.

Also, the manual shows two wires attached to the gas valve, yellow and brown. Do I test either or both of these? And how do I test it with my multimeter? The specs are:

AC voltage 10-50-250-500 V
Resistance RX1k and RX10k

Is this multimeter sufficient to test and diagnose??

Thank you

 

Set it for AC voltage 50 and place one lead on yellow and the other on brown at the gas valve.
You should get 24 volts ac to the valve after the ignitor glows.


The pressure switch should be open when the inducer is off and it should close when the inducer runs.

Does the inducer run when you turn off the stat?

 

Houston204,

"Does the inducer run when you turn off the stat?"

No. And now the inducer does not run with the thermostat on. This is identical to the irregular symptom I mentioned at the bottom of my opening post:

"One other twist: yesterday, a few times the sequence did not occur as above. Instead, something (the transformer maybe?) would hum, without the inducer fan running, nor did anything else in the furnace run."

Thank you again for your help!

 

Houston204,

I forgot to mention in my last reply that the red light stays on.

Here's a new development: the furnace is working! I know this should be good news, but I'm guessing that something weird is going on. I did nothing between when I turned the thermostat off, then back on, then turn on the power switch, then reply to you, except to turn the power switch on again. And Voila! The furnace is working!

Could the thermostat be the problem?

Thanks again.

 

The furnace has worked correctly for one cycle. It is now in the second cycle, working correctly. But I am still waiting for the gremlin to appear...

 

You can bypass the stat if this problem occurs to help verify if it is a stat problem.

R = 24 volt power
G = fan
W = heat
C = common
Y = cooling

Jumper R to W at the furnace to bypass the stat.

 

The problem happened again. Just as in my first post, the furnace cycled normally until time for the burner to ignite, which it didn't. Then, the furnace cycle restarted immediately, the burner ignited, and the furnace operated per usual, except that the yellow light blinked continuously (trouble code for a problem with the flame sensor.) But it kept heating fine.

 

That could signify a weak flame sense signal. That will cause problems.
Have you tried cleaning the flame sensor rod ?
If you haven't....it's only held in with one screw. Remove it and clean it with a Scothbrite pad.

 

Hi PJmax,

"Have you tried cleaning the flame sensor rod?"

I cleaned it and remounted it. The yellow light no longer blinks and the furnace came on first try. I will monitor it tonight and reply tomorrow.

Also, I got rid of the hum (see my opening post). I read another post about a hum in a furnace transformer. I used the suggestion to use a screwdriver as a stand-in for a stethoscope. I put the plastic end in my ear, then touched the screwdriver's tip to the transformer. Sure enough that's where the noise was coming from. The cure I read and used was to jam two toothpicks between the transformer and the sheet metal housing. Voila! The noise is almost completely gone!

Thank you for all for replying with such great ideas. Here's hoping that a combination of them does the trick.

 

Great news........good job

 

The gremlin is back. The same thing is happening with the furnace as detailed in my opening post. I waited a good while before reposting, so as to gather as much info as possible.

The furnace worked okay in the night until maybe 7:00 this morning. Then it started the same broken cycle of getting to the point of firing the burner, with no gas ignition. The red light shows 3 flashes for Pressure Switch Stuck Closed.

So, per a prior suggestion, after the inducer came on, I jumped R and W on the control board. The furnace fired. Then I turned the power off at the wall power switch. I took the jumper off, turned the wall switch on, and the furnace fired and ran normally twice in a row. The I left the wall switch on, and turned the thermostat up. About 15 minutes later, the furnace started the cycle on its own, but did not fire the burner. As with the original problem, the furnace would continue to recycle the same pattern, and not fire. (FYI, I have volts showing between R and C, Y, and G, and between W and C, Y, and G. But there is no voltage reading between R and W, at any time.)

To see if the problem is consistent, I repeated the scenario detailed above a second time, after letting the furnace cool. First, the furnace would not fire. Then I jumped it and it fired. Then I took the jumper off and it fired, twice in a row. Then I turned the thermostat up a few degrees, and it fired. However, unlike the scenario above, this time it did not fire again with the jumper off.

What I think I know is, if a jumper causes the furnace to fire, then the Pressure Switch is probably bad. This correlates with the Pressure Switch Stuck Closed problem code. But, if the Pressure Switch is bad, why did the furnace work without the jumper, after working only with the jumper? And even more perplexing, during my second, repeat scenrio, why did the furnace work with the jumper, then work without the jumper, and then not work without the jumper?

So, here are a few questions:

1) Could it be a switch? Or as I've read elsewhere, a vent problem? Or maybe water in a pipe or somewhere water should not be? Or, to try and ruin my Super Bowl Sunday, mojo, voodoo, or ju ju?

2) Since the problem is not consistent, which component is the most likely culprit? The first two replies I received in this thread point to the control board?.

My inclination is to purchase a Pressure Switch first, in case the contacts in the switch are connecting intermittently. Then, if that doesn't work, to buy a new control board. I'm far from being an HVAC tech, so if my observations are wrong, please sound off!

 

Why guess?

Use a multimeter to see if the pressure switch is actually sticking in the closed position, causing the diagnostic code to flash.

Connect your multimeter to the C terminal or the furnace chassis (ground).

Use the other test lead to check for 24 VAC at the pressure switch. Most pressure switches have two electrical connections.

One will have 24 VAC to it whenever the thermostat is calling for heat. The other should have 24 VAC to it only when the thermostat is calling for heat AND the inducer motor has come up to speed.

You need to identify which terminal is which.

You should have 24 VAC only on the one side before the inducer motor comes up to speed, and you should see that terminal energized when the inducer motor does come up to speed.

If both side are energize when the inducer motor starts, that indicates that the pressure switch is sticking in the closed position, and you should get the diagnostic error code.

If you get that situation --- replace the pressure switch.

But if the pressure switch IS opening and you are geting the diagnostic code, then you have an ignition control module or circuit board which is defective and needs to be replaced.

 

Hi SeattlePioneer,

I performed your test and the pressure switch responded as a good switch should. I also tried an ohm test. Removed the wires, set the meter to minimum ohms, touched probes to opposite terminals, and the meter read one ohm. And then the furnace fired. I know that the furnace will not fire eventually, so I will retest each time the thermostat calls for heat. I want to eliminate the PS as the problem. But having read other posts on intermittent PS problems, such as partial contact-point corrosion, making for irregular contacts, I'm still not convinced that the pressure switch isn't going bad, and therefor performing intermittently. However, my experience is very limited, so if you or anyone else thinks that the PS is good no matter what, please let me know.

Thanks again.

 

The furnace has run well since my last post. Based on yesterday's experience, it likely will fail again. I'll regroup until tomorrow.

 

Oh, there's a 75% probability that the pressure switch is the probability, 25% that it's the ignition control module I'd say.


But why go to the bother and expense of guessing when you can check and tell for sure?


People can do as they please of course. One of my aims here is to promote effective diagnostic procedures to identify problems rather than guessing and supposing.

 

Hi SeattlePioneer,

Thank you for your reply. I could not find the term "ignition control module" in my manual, nor either of the words separately, nor any combination of the words. I checked out the schematic, and the Location of Major Components chart, and used the "Find" function in my browser's edit tool. I came up with nothing. Is there another term for it. Do you mean the HSI igniter?

Anyway, I just got home from work, and I'm going to test the pressure switch. I turned on the furnace and it did not fire. So here's hoping I at least get a valid test!

 

Hi SeattlePioneer,

"One will have 24 VAC to it whenever the thermostat is calling for heat. The other should have 24 VAC to it only when the thermostat is calling for heat AND the inducer motor has come up to speed."

I conducted your test, and the pressure switch tested good. But this time, the furnace did not not come on, before, during, and after the test. So, it seems that the PS is good.

Also, I hope it helps to know that I tested the PS by the other method I mentioned a few replies back:

"I also tried an ohm test. Removed the wires, set the meter to minimum ohms, touched probes to opposite terminals, and the meter read one ohm."

I performed the ohm test two ways:
1) with the wires attached to the PS, and no electricity. This is when the meter read one ohm;
2) with the wires off the PS. The needle did not move.

So, after the testing, I jumped from R to W, turned the electricity on to the furnace, and it fired up and ran normally.

Then, I turned the electricity off to shut off the furnace, pulled off the jumper wire, turned the electricity back on, and the furnace fired and ran like normal.

Does this scenario point to one component? Is there another test I can perform? Thanks again!

 

Since my pressure switch tested good every time I tried, and the furnace is acting goofier and goofier, I bought a control board online. We'll see...

 

Probably a good move. Keep us posted.

 

I agree with PJ Max --- replacing the control board/circuit board/ignition control module is the right thing to do since you eliminated the pressure switch as the problem.




Glad you checked the pressure switch!

 

still waiting for the part...

 

I snapped the new control board in and the furnace works. I will offer a yeah or nay sometime tomorrow.

 

A day and a half later after installing the new control board and the furnace works great. Thank you all for hanging in there with me.

FYI, to those who read this thread and want to know where to buy this specific control board, I offer the following info: look for the board number 903106. It is the Nordyne Miller Integrated Control Board Kit for Nordyne G3, G4, G5, G6, M2 & M3 furnaces. My furnace number is G6RA. The number on my old board is obsolete (903019). The new board is identical to the old, but with the new number. Again, 903106 is the board you want. It is easy to install.

A major cold snap is headed our way in Colorado Springs, and my entire family is grateful for all your help. Again, thank you all so much.

 

to piggy back on this forum...i am having a near identical issue. However, i have replaced my board...checked/ran the inducer motor 120v and replaced the HSI.

My problem occurs whenever i remove my T-Stat jumper(R&W) and replace the original T-stat wires...the furnace will remain in the idle posistion. Nothing happens. No inducer motor...zero.

Is my problem a faulty T-stat? Or am i missing something.

Th furnace is identical..Nordyne model # KG6RA.

Thanks for your help

 

Are you saying that if you connect the red and white wires that the furnace works normally ?

Do you have the jumper on the thermostat between R and Rh or Rc and Rh ?