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Central furnance not working properly

Have a Amana a/c heater central furnace. Model number PGA30R0452A. The a/c part works fine. The heater part does not turn on sometimes. We have to keep turning it on and off to get to work. No matter what you hear a slight humming when we turn it on just it doesn't always blow air out of the vents. It also does not always kick back on once the temp. has dropped and should start heating the house again. We have programmable thermostat. Any suggestions to whats broken or breaking. My husband would like to fix it himself we dont really have the money to call someone out to do it. Thanks.

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  • wildcat1828 Nov 18, 2009

    Sorry the model number should be PGA30B0452A

  • wildcat1828 Nov 18, 2009

    I now have a copy of the Service Instructions in pdf


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central furnance not working properly - 2df7444.jpg
On some gas furnaces and heaters, a plug-type door covers the pilot light assembly. To gain access to the pilot burner, pull the door out of the furnace housing. On other units, remove the panel that covers the pilot and gas burners.

The pilot light controls, reset buttons, gas valves, and thermocouple are usually contained in an assembly at the front of the furnace. The furnace limit switch is located on the plenum (main chamber) or main duct junction on the upper housing of the furnace.

The Pilot Light

The pilot light on a gas furnace can go out because of drafts. To relight the pilot, follow the manufacturer's instructions exactly; they are usually fastened to the furnace. If instructions for relighting the pilot are not provided, follow this general procedure:

Step 1: Find pilot light assembly. It typically has a gas valve with on, off, and pilot settings.

Step 2: Turn valve to off and wait three minutes.

Step 3: Switch valve to pilot setting. Hold lighted match to pilot opening while you push reset button on pilot control panel. Keep this button depressed until pilot flame burns brightly, then set valve to on position.

Step 4: If pilot flame won't stay lit, opening may be clogged. Turn gas valve off, and clean opening with piece of fine wire. If it won't stay lit after several attempts, you may have faulty thermocouple. If pilot flame still won't stay lit, call professional service person.

Some furnaces have an electrical system to ignite the gas; in these systems there is no pilot light. Instead, an electric element heats up and ignites the burners. If this electric ignition system malfunctions, call a professional service person.

Replacing the Thermocouple

The thermocouple is a gas furnace component located near the pilot light burner. It is a safety device that shuts off the gas if the pilot light goes out or the electric igniter fails.

If the pilot light won't stay lit, the thermocouple may be faulty and should be adjusted or replaced. To adjust the thermocouple, you must tighten the thermocouple nut with a wrench. Take care not to apply too much pressure to the nut -- just tighten it slightly. Then try lighting the pilot. If the pilot won't stay lit, replace the thermocouple with a new one of the same type. Here's how to replace a thermocouple:
Step 1: Unscrew copper lead and connection nut inside threaded connection to gas line. Under mounting bracket at thermocouple tube, unscrew bracket nut that holds tube in place.

Step 2: Insert new thermocouple into hole in bracket. Be sure steel tube is up and copper lead is down. Under bracket, screw bracket nut over tube. Push connection nut to threaded connection where copper lead connects to gas line. Make sure connection is clean and dry.

Step 3: Tightly screw nut into place, but do not over-tighten. Both bracket nut and connection nut should be only a little tighter than if hand-tightened
Limit Switch

The limit switch is a safety control switch located on the furnace just below the plenum. If the plenum gets too hot, the limit switch shuts off the burner. It also shuts off the blower when the temperature drops to a certain level after the burner has shut off. If the blower runs continuously, either the blower control on the thermostat has been set to the ON position or the limit control switch needs adjustment. Check the thermostat first. If the blower control has been set to ON, change it to AUTO; if the blower control is already on AUTO, the limit switch needs adjusting.
To adjust the switch, remove the control's cover. Under it is a toothed dial with one side marked LIMIT; don't touch this side. The other side of the control is marked FAN. There are two pointers on the fan side; the blower goes on at the upper pointer setting and turns off at the lower pointer setting. The pointers should be set about 25 degrees apart. Set the upper pointer at about 115 degrees Fahrenheit and the lower one at about 90 degrees Fahrenheit.
I hope this helps ancentral furnance not working properly - 14674e4.png!

Posted on Nov 18, 2009

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There is something wrong with that model number. I can tell you though that the problem you are talking about it one of probably two simple things.
1. The ignitor. There is a filament in the furnace that ignites the gas. These burn out. The easiest way to check it is to turn the thermostat up and see if you can see it glowing like a lightbulb. You can find it by looking for and item that looks like a light bulb filament with two wires coming off it and it is in the burner area.
2. Some units have a flame sensor. There is a metal rod that extends into the burner area and it has a wire attached to it. The rod gets corroded and needs to be cleaned or replaced. Remove the screw that holds it in and unhook the connector on it and use a very very very small grit sandpaper or better yet a cloth and rubbing alcohol to clean it.
I would start with those two items.
It could be more than this though. It could be the board on the unit that controls everything.

Posted on Nov 18, 2009

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