i have a rheem 90 plus furnace that is about 17 years old. It will not stay on.

Can you provide more details about your problem? When was the last time you had the unit serviced?

The blower turns on, the ignitor ignites, the gas valve opens and the flames come. After 5 seconds, the gas turns off. After two cycles, when the gas turns off, the fan goes on. I have replaced the board, the flame senor and two pressure switches at this point. There are three lights in the unit. The first is the flame light which is not on at all. The other two lights are ok and power which are both a steady green color.

Do you have a model number of the furnance? To start I would check the combustion air inlet and the vent pipe for restrictions. Is the flames steady when burning without the blower? Do they remain steady with the blower on or do they blow around? Check the hose that is connected to the inducer draft motor and see it it had any water in it, check the condensate drain and make sure it is not stopped up.

No restrictions. The flames go out after 5 seconds from coming on. The model # is RGRA-07EMAES

Your flame sensor is not seeing a flame. You said you replaced the board. If the new board is part number 62-24084 it is a new upgrade board and requires a sensor upgrade or it will not work. See pitcure below. Rheem Tech support: Reference 62-24084 upgrade. ALL FURNACES BEFORE 1994 WILL NEED A NEW FLAME SENSOR KIT OR THE NEW CIRCUIT BOARD WILL NOT WORK. If your existing Circuit Board has 2 green lights and NO Amber light. You will need to upgrade your new circuit board with a FLAME SENSOR KIT. If there is no flame sensor then you will need to install one, run the supplied wires per the instructions to the new 3 light control board. ( 2 Green & 1 Amber Light) If there is an existing flame sensor, check the wiring, if it is spliced into one of the Hot surface Ignitor wires it will need to be disconnected and then run the supplied wires per the instructions to the new 3 light control board. ( 2 Green & 1 Amber Light)

Flame sensors Installed with 2 Light Boards was spliced into the Ignitor wires. Flame sensors Installed with 3 Light Boards must wire back to the control board. ALL Rheem HOT Surface Ignition Furnaces should be equipped with a Remote Flame sensor. If the Furnace does not have a Flame Sensor, a remote flame sense Kit should be installed.

stanhvac1, THANK YOU SOOOO MUCH !!!!!! My husband purchased and installed the upgraded flame sensor kit and I'm happy to say my heat is working !!!!!. We, most likely, would have purchased a new furnace had I not received your expertise. The supply house that we purchased the part from will now put a note in their system of this circumstance to help their future customers avoid a week without heat like my family went through. Thanks again !!!!!!

Thank you for the update. It is good to hear that I could help you out. I am sorry that it took me so long to isolate your problem but I needed the additional information I ask for and received on your end. If we can be of any more help please let us know. You can find me on face book: Stan Chaney HVAC if you would like to post a comment. Stan Stan Chaney HVACR Commercial Refrigeration

HI Stan,

Sorry to bother you but my furnace is out again. It has been working up until just an hour ago. Now the furnace won't come on at all. Same two green lights, no amber light. Prevously, it would start, ignite and flame for 5 seconds and go off. Now it won't even turn on. There is a black cylinder that two black hoses tie into on the bottom half of the furnace. It was filled with water. I disconnected the tubes and turned the black piece upside down to let all of the water out of it. Turned it upright and connected the hoses back. Nothing !!! Any thoughts???

You probably have water still in the hoses, hose that comes from the black trap to the inducer blower (see pitcure below), or the pressure switch. Make sure all lines are free of water and no restrictions. We fixed the other problem, this is unrelated to that issue. The amber light will not come on until the burners fire. Sorry I am taking so long to answer you but we aree busy here due to the cold snap. I will see if homeowner has any more input on this also.

mg1996, did you have the issue resolved? Sorry, I'm coming in very late in the game, but I'd be glad to help if I can. Also, very interested in learning about the outcome, in case other users have a similar problem. When you have a minute, please post an update if you can.

I have the same furnace as the previous conversation. RGRA-07emaes and we have replaced blower motor, and board. Now the furnace is just coming on for about 5 minutes and then shuts off and then kicks back on again but, not reaching thermostat setting for room.