I just bought a house with a Criterion RGLH-07EAUER down flow furnace. This is our first home, and when we had the inspection the furnace worked just fine. I had noticed that the unit was very dirty though, so I had a technician come over and clean the blower by taking it out of the furnace and service the A/C as well. The A/C works great, but when we tried the heater, it wouldn't work properly. The accumulator blower kicks on, then igniter heats up, gas turns on and flames start. Then a few seconds later I hear a click, the igniter starts to dim and the flame shuts off. I will see 3 quick green light flashes and then it will then cycle once more, but this time when the flame shuts off the blower will kick on and run for a few minutes. The technician told me that I needed a new accumulator motor because the old one was making a loud noise and took a while to get up to speed. I bought a new Rheem 70-24157-03 Inducer Blower Motor 10701 and installed it with no change in the results. I then decided to replace the flame sensor, and this did not help either. I thought maybe polarity was switched so I switched the white and black leads incoming to the unit and no change in results. I saw a similar post about blower leads hooked up to "cool" "heat" and parked leads. I had a red wire coming from the blower motor that is capped off which I found strange, but I doubt the technician would have changed anything that was hooked up because the unit worked before he serviced it. He would have had to strip the wire and cap it off so I assumed it was fine. Black wire runs to "cool" and yellow runs to a "Heat" and blue runs to the "mi" terminal. Any help would be appreciated. We are trying to at least get one winter out of this thing before we need to replace it. Thanks! The people who owned the house before us did not take care of this unit at all. Also, I did replace the filter.

 

Welcome to the forums!

3 green flashes indicates a limit problem. Probably not the pressure sensor since the pilot ignites and burner turns on. More likely a rollout or temp sensor tripping. Make sure the flue is not obstructed (critters love to build nests in them during off season).

 

A classic flame sensor problem except when it is you don't get the three flash fault.
This furnace lists a direct spark ignition system yet you are talking about an igniter ?

It's not a blower or blower wiring problem.

document-rh.aspx?name=rglh-specification-sheets

 

It does not have a direct spark ignition system. It has an ignitor coil that looks similar to the image in the link below:

http://ww2.justanswer.com/uploads/ai..._ignitor_2.jpg

I thought it was the flame sensor as well, so I replaced the sensor and I am having the same issues. I tried to lightly wipe off the new one after the first installation didn't work, but that yielded the same results.

Also, I checked the flue and from what I can see, everything looks to be clear.

 

I did run a check on the sensor to see what kind of amps I was getting when the flame was on. I am only getting between .1 - .2 uA with a brand new flame sensor. I did notice a deep scratch on the sensor when I installed it. Are these sensors really that sensitive? Is there something else that could be causing such low values? I cleaned it off and got similar values. Any installation tips to make sure I don't ruin the next one I get in?

Thanks!

 

Ok... just to set your mind at ease. The flame sensor is nothing more than a rod of metal with a wire connected to it. It's called the flame sensor but it doesn't sense a flame. It basically should last a lifetime. You just keep cleaning it every year. I use a green Scotchbrite pad. Some use steel wool and others use fine emery cloth.

The flame sensor circuit works by the flame conducting current from the flame sensor rod thru ground. An AC signal is applied to the flame rod. It passes thru the flame and becomes a DC current which you can measure. That measurement shows how well the flame is conducting.

So basically the signal leaves the control box on the single wire. Goes thru the rod, thru the flame to ground and back to the control board on ground. A loop. Any weak link in the loop affects the circuit. Weak/dirty grounds are a typical problem.

Important things that upset the circuit...
1) The rod must be engulfed in the flame.
2) The ground connections and mounting screws must be solid on the control board.
3) The mounting screws on the burner must be clean and tight.
4) While observing the DC current meter.... you can carefully bend the mounting bracket for the rod so that the current goes up to a peak point.

 

If you are measuring the flame rectification current correctly, you are not getting sufficient current to keep the burners lit.

GOOD flame rectification current is typically about .5 uamps DC.

at .1 uamp DC the flame will typically be shut off as you describe.

The most common reason for poor flame rectification current is a dirty flame sensor, but since you have replaced that, that's not the problem.

My #1 concern would be to check that the circuit board is well grounded to the furnace sheet metal chassis. Poor grounding will result in poor flame rectification current.

#2 concern would be that the AC voltage being applied to the flame sensor is too low due to a relay on the circuit board that has worn out contacts.

Measure the AC voltage being applied to the flame sensor by the wire and report that here.