My heating systems was working up until yesterday morning. I smelt a gas leak in the garage near the hot water heaters. Had Atmos Gas come & check to verify and turn off gas. The plumbers came out and repaired the pipes that were leaking. The gas company came back out, turn the gas back on, relit all gas appliances and check the heating systems. When he tried starting the up stairs unit my thermostat would attempt to start the heater but show a -AC, blink the indicator lights, make a sound like some relays were trying to kick in, but it would never start. I swapped the top section of the thermostat with the one down stairs and both are working down stairs, but both are failing upstairs. What does -AC mean? Do you think the base electronics of the upstairs Thermostat has failed? Or could there be a new gas issue that has occurred since the gas pressure has been bought back up. Need help need heat upstairs.

Brand and Exact model of thermostat? Cannot do much without that.

The problem you are having is with the thermostat not the gas at this time.

You have dual thermostats?

Do you have one or two furnaces?

Are these furnaces or a boiler system?

Put the parts from the thermostats back where ever you changed them from.

Post back with the info.

The Thermostats are Honeywell Chromotherm III's. There are two separate thermostats, two separate furnaces. Parts have already been return to rightful units.

Quote:

---

Originally Posted by hvac1000

Brand and Exact model of thermostat? Cannot do much without that.

The problem you are having is with the thermostat not the gas at this time.

You have dual thermostats?

Do you have one or two furnaces?

Are these furnaces or a boiler system?

Put the parts from the thermostats back where ever you changed them from.

Post back with the info.

---

The Brand is a Honeywell Chromoterm III. There are two separate thermostats and two separate furnaces in the home. The parts have been return to their rightful units.

Honeywell Chromotherm III's does not help

I have to look up by exact model number.

Honeywell has made 20 different series 3 thermostats. I will also need the subbase model number. That is the item the thermostat hooks to on the wall.

The Honeywell Thermostat model number is T8601C1047. Not sure but there maybe a 1 after the seven but it is turned horizontal.

Quote:

---

Originally Posted by jwigfall

The Honeywell Thermostat model number is T8601C1047. Not sure but there maybe a 1 after the seven but it is turned horizontal.

---

Your systems AC power has been lost

Read page 3

http://customer.honeywell.com/techli...0s/69-0577.pdf

Quote:

---

Originally Posted by hvac1000

Your systems AC power has been lost

Read page 3

http://customer.honeywell.com/techli...0s/69-0577.pdf

---

Is there anything I can do to reset the AC power besides the circuit breakers. Or is there something on the heater that can be reset. It was just working yesterday morning, it seems like there something I can do.

OK first install new fresh batterys correctly into the thermostat. Then post back with the results.

Quote:

---

Originally Posted by hvac1000

OK first install new fresh batterys correctly into the thermostat. Then post back with the results.

---

New batteries installed. Thermostat switches on & off showing Temp then -AC.

Looks like you have lost the A/C power at the furnace. It could be a transformer or the furnace power switch is turned to the off position. It could also be a broken wire going to the thermostat.

Quote:

---

Originally Posted by jwigfall

New batteries installed. Thermostat switches on & off showing Temp then -AC.

---

New batteries are installed and I performed the self test of page 3 & 4 of the Honeywell spec sheet. It tries to start but I still get the -AC on the screen. I also measured the AC test points of C & R and it measured 28.5 Vac. There are contact points that transfer power and info from the thermostat to the base but I don't which pins are for what and the Honeywell spec sheet never covered that. Are there any other measurements I can make?

Guessing: Could it be an Air Cleaner warning message?

In other words time to reset and change the air cleaner. This should only be a warning though.

If you have followed the info I have posted from the Honeywell site I do not know what else to tell you. It might be thermostat time.