Rheem gas furnace RGLG-07NAUER fan won't activate via t-stat

Dave_Anderson

Hi, first post here, hopefully I've collected enough detail to make a good start narrowing the problem. I'd be grateful if someone could pass along any specific info about operation of this controller beyond the brief bit on the labels, further troubleshooting steps, or anything at all that might point me in the right direction. I tried the Rheem site and they show no documents at all for this part number(or shortened variants of the part number). All troubleshooting info I have been able to find focuses on a failure of the unit to provide heat, which is the one thing it does right.

Symptom: When I try to manually activate the fan via the t-stat, there is a "click" from the control board but the fan does not actually start. When the t-stat calls for heat, everything works as it should. The burner lights, the fan blows, etc.

I'm pretty handy and should be able to perform any reasonable test. I suspect a bad relay but it doesn't make sense to me that there would be one relay for manually activating the fan and another for operating the fan when heat is called for. I would like to get some expert advice before tearing in and testing the relays for correct operation(e.g. apply 24v to coil & check contact operation). I found a replacement board online and after seeing the price I'm hoping it's something simpler.

OK, some details would help, eh? Note that we bought this house earlier this year so I have no history on this unit. BTW it's a horizontal unit.

Furnace:
Mfg: Rheem
Model: RGLG-07NAUER
Serial: CU1D302 F0893 6421
Converted with kit EP70H so now is model RGLG-07NAUET per the conversion label, though I doubt this relates to the problem -- I put a similar label on my gas dryer when I converted it to propane, all I did was modify the burner and replace the gas valve.

T-stat:
Mfg: Honeywell
Model: TH8110U1003
Serial: 302001000622252
Manual available @ bottom of page here.

Here is a shot of the circuit diagram inside the unit:


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T-stat wiring at control board:


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T-Stat wiring at T-stat(Note, I added the blue jumper after reading the Honeywell manual, no help):


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This relay looks like it's been a bit hotter than intended. Also, I can't figure out from any of the info attached to the furnace what the DIP switch is for.


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I've posted a few more photos here, larger sizes are available from the small flyout menu that appears when you mose over a photo at that link.

scottmcd9999

So when you turn the Fan switch (on the stat) to ON, the blower does not turn on? But otherwise everything else works?

The board had a FAN terminal (just below the relays, between the Red and Blue wires). Move the RED wire to that terminal and see if that fixes it. The FAN terminal is used to provide blower power when the fan is turned ON.

DIP switches are used to control timing for blower on/off delay, if I remember correctly.

There should be no jumpers on those tstat connections.

Acomfort

see if your getting voltage across your fan terminals after the relay clicks

Acomfort

this is true and you wouldn't need it if you don't have cooling

ben's plumbing

yep scott your right dip switches used for timer fan on and off...

Dave_Anderson

Thanks Scott. I'll try moving the red wire when I have a chance a bit later today.

I forgot to mention, I added the jumper on the t-stat in an attempt to get the fan to run when the t-stat calls for cooling, e.g. when it gets too hot inside.

turnermech

you do need the jumper at the tstat. you asked does the board have separate relays on it for heat blower and fan only blower in you OP. It does. it will actually have three relays IIRC. heating blower, fan only blower, and cooling blower. You need to check for 24 volts on terminals C and G with the fan on. then check for 120 volts beetween the motor common lead (most offen white) and fan on lead ( best guess would be blue but may not be). heat speed lead would most likely be red and cooling speed would be black.

Dave_Anderson

Thanks everyone for the help! Everything is now working as it should. The heat cycle works properly and now I have manual control over the fan. The one thing I'll want to fiddle with as I have more time is the black/red fan wires. IMO the wiring diagram is suspect, it doesn't even show the fan terminal.

However, as it sits now Black is connected to Heat, Blue is connected to Cool and Red is connected to Fan.

The diagram shows Black is connected to Cool(HI), Blue is connected to an unused terminal and Red is connected to Heat(LO). Fan is not shown.

Red WAS connected to M1, labeled as a "Park Terminal" before I moved it to Fan.

So, my understanding is I can select different fan speeds for different operting modes. If I experiment a bit I can find the relative speeds of power @ RD, BK, BU.

Please stop me if you see any pitfalls, but I think I want the lowest speed when heating, and my preference is to have the highest speed when just running the fan. I guess the pointed question would be, should heat be the lowest speed? Seems like it should, to extract the most heat from the burner.

turnermech

black should be highest speed. blue med. red low. the red or blue would typically be for heating. Black would be for Cooling (which you don't have so does not matter)