Heater not heating
- Thread starter careingemt
- Start date
The igniters on these are spark gap electrodes similar in function to a gas engine spark plug in operation. I doubt it is the problem. These units have a bad track record of board problems with broken solder joints. There are also several safety switches that any one of will prevent the unit from firing if conditions are not right. what exactly is the unit doing. Is the draft fan coming on? If so can you feel air flow from the exhaust? If the fan is nor running or is running and not moving air out the exhaust then that is where to start. I have seen these with the fan blades completely rusted off but the motor still spins.
Where in PA are you?
Dan
Where in PA are you?
Dan
I have the switch on dial set to full cold
Turn the dial to full hot ... Half way through turning dial towards hot I hear the draft fan turn on... Put my hand over the vent and I feel cool air blowing. The heater is only 7 years old
20 minutes north of Pittsburgh
Turn the dial to full hot ... Half way through turning dial towards hot I hear the draft fan turn on... Put my hand over the vent and I feel cool air blowing. The heater is only 7 years old
20 minutes north of Pittsburgh
OK, ... Several things need to happen for one of these to work. First is the call for heat. Switch on and thermostat turned up causing the fan to come on is good in that we have power and that the fan and thermostat are working. When the fan comes on, one of the proving switches is connected to the fan to check that it is working properly. This is set by a vacuum switch via a small hose connected to the blower housing. The opening that this is connected to may be clogged and not allowing vacuum to set the switch or the hose is leaking. The good news on this is that a simple jumper wire is all that is needed to test this.
If the switch is working the next sequence of events is for the flow switch and over temp switched to allow the 24 volt signal to get back to the control board signaling that everything is ok. The best way to test all of this is to use a volt meter. If the switches are all set properly the board will then signal the igniter to start sparking. This unit uses a system similar to a spark plug on an engine in that it fires a spark across a gap to ignite the gas. These are very robust and rarely fail (more on this later as it is a dual function part) When the board signals the spark it also opens the gas valve allowing gas flow to the burners. Once the burners are lit the second function of the igniter takes over. This is the flame sensor portion. It tells the board that the flame is lit and to allow the gas valve to stay open.
As I mentioned earlier, the boards in these do fail. Usually it is a bad solder connection. The two places I see the failure the most id the power connection pins and the center connection for the spark coil. I have had the power connection pin problem happen and still have the blower work but the low voltage side not work.
Hope this helps.
Dan
PS: 3 hours north of you. A little to far to travel
If the switch is working the next sequence of events is for the flow switch and over temp switched to allow the 24 volt signal to get back to the control board signaling that everything is ok. The best way to test all of this is to use a volt meter. If the switches are all set properly the board will then signal the igniter to start sparking. This unit uses a system similar to a spark plug on an engine in that it fires a spark across a gap to ignite the gas. These are very robust and rarely fail (more on this later as it is a dual function part) When the board signals the spark it also opens the gas valve allowing gas flow to the burners. Once the burners are lit the second function of the igniter takes over. This is the flame sensor portion. It tells the board that the flame is lit and to allow the gas valve to stay open.
As I mentioned earlier, the boards in these do fail. Usually it is a bad solder connection. The two places I see the failure the most id the power connection pins and the center connection for the spark coil. I have had the power connection pin problem happen and still have the blower work but the low voltage side not work.
Hope this helps.
Dan
PS: 3 hours north of you. A little to far to travel
swamprat69
Well-known member
This is the schematic diagram for the HD100ID. It looks like the whole system is 120 volt AC. The gas valve should be marked as 120V as I don't see a transformer in the schematic. If the combustion blower runs, then the water flow switch has proven and closed its contacts. The last 3 safeties needed to power the ignition module are the 2 temperature limits and the air pressure switch. To check these, use a multimeter set to AC volts and put 1 lead on the neutral contact of the ignition module (normally a white wire) and the other lead on the other 120 volt power in contact of the ignition module (normally a black or colored wire) . If it does not read 120 volts then 1 of those three safeties is open. Keeping the lead on the neutral contact of the ignition module you can then check backwards through the three safeties to see where you are losing power. The safety that reads 0 volts on one side and 120 volts on the other side is the one that is open. If you have 120 volts power in at the ignition module, you should have a spark at the ignitor and power at the gas valve. If you have no spark then either the ignitor is dirty or the ignition module is bad (also if this is the case you would smell raw gas in the combustion motor exhaust). If you get a spark but the burners don't light off, then either the burners/orifices are so dirty that they are preventing the burners from lighting (you would get raw gas odor from the combustion motor exhaust) or the gas valve is not opening ( no power from ignition module or failed gas valve if you have 120 volts at the gas valve).