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I have a Chromotherm III programmable thermostat that now…

Customer Question
I have a Chromotherm...

I have a Chromotherm III programmable thermostat that now shows -AC and does not turn on the the air conditioner. I changed the three AAA batteries for new, but no luck.

Contractor's Assistant: Did you double-check the thermostat's settings? And what about the filters?

Furnace filters?

Contractor's Assistant: Do you plan on doing the work yourself?

I can change those also but they are not old.

Contractor's Assistant: Anything else we should know to help you best?

The air conditioner is brand new and was working fine. The thermostat settings are unchanged. Suddenly not working and shows the error -AC

Submitted: 11 months ago.Category: HVAC
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Answered in 23 minutes by:
10/7/2017
HVAC Technician: airheatman, HVAC Technician replied 11 months ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,545
Experience: Furnace, A/C and heat pump specialist.
Verified

AC indicates we have no low voltage power from furnace.

Look for a float switch first in drain that may be blocked up breaking the circuit.If you have one, lift float and see if error goes away and system runs.We will go from here.

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Customer reply replied 11 months ago
Could not find any such item. The drain is from the furnace is just a straight pvc white pipe and a black rubber/plastic hose.
Customer reply replied 11 months ago
Sorry I do not hear on the telephone.
HVAC Technician: airheatman, HVAC Technician replied 11 months ago

OK remove panels on furnace and look on control board for a small 3 or 5 amp fuse and see if it is blown.

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https://i.imgur.com/kYe4Epz.png

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