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kzuk59 · Oct 26, 2005, 04:50 PM

If there is someone who can guide me I would appreciate it. I recently bought a house that has a Delco-Heat Condionair by GM. The pilot light is lit, but I can't get the heat to come on. I can't find a switch, directions, or anything else. Am I missing something? Advice will be extremely appreciated!

labman · Oct 27, 2005, 07:32 AM

Most thermostats have a switch heat/off/cool. If the switch is in the heat position, and the thermostat set above room temperature, the heat should come on. The blower shouldn't start until the air in the furnace warms up. If the thermostat has an auto/on switch for the fan, try on. If the fan doesn't come on, the thermostat may not be getting power. Could be a fuse blown on the control board, or as simple as the switch for the filter housing not being closed. Check around, and post back if you don't find the problem.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

labman · Oct 27, 2005, 08:15 AM

Most thermostats have a switch heat/off/cool. If the switch is in the heat position, and the thermostat set above room temperature, the heat should come on. The blower shouldn't start until the air in the furnace warms up. If the thermostat has an auto/on switch for the fan, try on. If the fan doesn't come on, the thermostat may not be getting power. Could be a fuse blown on the control board, or as simple as the switch for the filter housing not being closed. Check around, and post back if you don't find the problem.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

kzuk59 · Oct 27, 2005, 10:31 AM

Thank you labman. However, here's the thing... there is NOT a switch to be found! Nothing! There's a silver box outside of the unit, but there is nothing in that either. Just two wires and a round silver plate. There isn't a switch on the thermostat, just the dial, and there are no switches on the unit, around the unit, away from the unit, nothing! I think I'm going to have to call someone in. I'll have to admit defeat here! :( Thanks for your help anyway!

labman · Oct 27, 2005, 10:43 AM

I wouldn't give up yet. I hate to ask this, but you did try the breaker? Even if it looks on, it may not be. Turn it all the way to off, and then all the way back on. I would make sure you are getting power to the thermostat before calling help in.

Sorry about the duplicate posts, a lot happening here this morning.

kzuk59 · Oct 27, 2005, 03:01 PM

Thank you again labman! However, I did check the fuses, turned them on and off. I have a small ranch, so places to look for switches or anything else is easy. Nothing is here :( I did call the gas company and they can send someone out Tuesday the earliest. I'm hoping it warms up for now. In the meantime, I will keep looking and trying. Thanks again. If you have any other ideas, PLEASE pass them along to me!!

labman · Oct 27, 2005, 04:21 PM

Could be a long 5 days. Go out and buy a voltage detector. There are several brands. I have a GB Instruments GVD-505A, less than $15 at Home Depot. Touch it to a hot wire, and the end glows red. Find the doodad that lights it on one side, and not the other, and you have the culprit. The one I have is adjustable and can do 24 volts too.

You are not getting the 24 volts to the gas valve or it doesn't work. I would start at where the house wiring comes into the furnace. If you don't have power at least as far as the safety switch that opens when you take the cover off, work back to the fuses or breaker box. If you have power at such a switch, hold it down while you check the transformer, its secondaries, the red wire to the thermostat, and the white wire coming back to the gas valve. The gas valve is between the gas pipe and the furnace burner. It should have a white and a blue wire running to it.