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MatthewJ · Feb 9, 2008, 12:38 PM

I have an American Standard Furnace Freedom 80 Comfort-R
The Main Gas Valve Solenoid does not energize, no 24volts from the "Pressure switch 2nd stage". [referencing the diagram on inside door panel].

The "lo fire" 1st stage solenoid ALWAYS gets 24v after pilot light is on for 20 seconds.
The "hi fire" 2nd stage solenoid does not get 24v from the "Pressure switch 2nd stage"

[Sometimes, the Main Gas Valve, 2nd stage, does get 24v and the burner comes on.]

Can you offer any advice or can you direct me to where I can get further information on:
Why am I not getting 24v from the "Pressure Switch 2nd stage"?

As I've said, very seldom it will work as designed and the burner will come on,, THEN it will stop working, no 24v to 2nd stage solenoid.

T-Top · Feb 9, 2008, 07:13 PM

Did you look at the fault light on the furnace to see why it was faulting out?

MatthewJ · Feb 9, 2008, 07:56 PM

Thanks for the reply. I have many details but no answers :-(

Yes,, after 3 auto-retries the error code flashes "Retries Exceeded" and the exhaust fan comes on and stays on.

Example of NORMAL OPERATION:
1- the pilot light comes on for 20 seconds.
2- I hear a SOFT CLICK [nothing is observed] 24v to "Lo Fire 1st Stage Solenoid".
3- [after 2 seconds] I hear a second LOUDER click, 24v to "Hi Fire 2nd Stage Solenoid".
4- [after 2 seconds] burner comes on.

Example of my problem:
1- the pilot light comes on for 20 seconds.
2- I hear a SOFT CLICK [nothing is observed] 24v to "Lo Fire 1st Stage Solenoid".
3- [after 2 seconds] I hear a second click, NO voltage to "Hi Fire 2nd Stage Solenoid".
4- Voltage removed from "Lo Fire 1st Stage Solenoid".
5- Pilot Light goes out.
6- After about 1 minute, back to step #1.

I've replaced the "2 Stage Gas Valve Assembly" [both solenoids]. The strange thing is it worked OK for 2 weeks. Then the same problem returned.

Example of wiring from Diagram and my tracing through cabinet:
- Both solenoids share the same "COMMON", labeled as such and plugs into the Controller Board.
- The 2nd stage solenoid "hot" wire goes to a tab on the "Pressure Switch 2nd Stage".
- From that SAME TAB on the "Pressure Switch 2nd Stage", it goes to the Controller Board connector labeled "Pressure Switch Input".
- The other tab on the "Pressure Switch 2nd Stage" goes to the Controller Board connector labeled "Gas Valve High 2nd Stage". I checked this tab with my multimeter and it showed 24v for only a moment when the pilot light first comes on.
- The 1st stage solenoid "hot" wire goes directly to the Controller Board connector labeled "Gas Valve Low 1st Stage". This solenoid seems to work properly all the time.

Please, any help would be appreciated.

T-Top · Feb 9, 2008, 08:14 PM

Your losing 24 volts on 1 and 2. the gas valve will keep 24 volt on stage one when stage two is on. It may be a pressure switch or restriction in vent or bad gas valve. You can lock your system in low fire from just switching a dip switch on the control board to see if it will work with low fire only.

MatthewJ · Feb 9, 2008, 08:25 PM

Thank you.

I don't think it is a "restriction in vent" because I disconnected vent hose to the Pressure Switch and the furnace would do nothing. No Pilot Light, No activity, Nothing.
"Bad gas valve" should not be problem since it is factory rebuilt assembly.
MAYBE PROBLEM IS PRESSURE SWITCH??

I like the idea of "dip switch" setting to lock system in low fire mode.
I don't know what to expect, me being a novice :-) but I will try and find dip switch setting on diagram and try it.

Thank you VERY much

T-Top · Feb 9, 2008, 09:32 PM

I was talking about the exhaust vent on the furnace. The inducer motor ramps up for high fire if the 2nd stage pressure switch fails to close(do to restriction) the furnace will shut down. You can also lock it in 1st stage by disconnecting w2 thermostat wire on the furnace control board. If it works it gives you heat until you figure out the problem.

MatthewJ · Feb 9, 2008, 10:18 PM

Oh, OK, "exhaust vent". [If I understand you correctly.] I do not know if there is a "restriction" in the 2nd stage pressure switch causing it to fail to close.

I would like to try your idea of "disconnecting w2 thermostat wire on the furnace control board". --- HOW CAN I FIND THIS W2 THERMOSTAT WIRE?? Can you tell me how it will be labeled?? Any information on identifying it would be greatly appreciated??

Thanks much

P.S. Someone mentioned a "dip switch" setting,, but I found NO dip switch setting to lock in 1st stage!!

MatthewJ · Feb 9, 2008, 10:27 PM

I found "W2" on the Thermostat Terminal Block!!

THERE IS NOTHING CONNECTED TO "W2" ON THE THERMOSTAT TERMINAL BLOCK!!

eagark · Feb 10, 2008, 02:10 AM

It is dificult to diagnose this without more info, and possibly some tests. For instance, if you live at a significant altitude like Denver, it is possible the pressure switch cannot maintain a closed position due to atmospheric conditions, and you will need a high altitude pressure switch. Also, there may be a small leak somewhere in the pressure lines resulting in loss of vacuum. You need to put a vacuum test on the line going to the switch, and check the vacuum. Also, I would check sequence of operation, if this is a new problem, or if this is a condition that has existed since the furnace was installed.