My readout screen is blank on my Honeywell Chronotherm IV plus. I have a 5 zone system, and the other 4 work fine. Pushing buttons does not help.

Exact model number

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Originally Posted by hvac1000

Exact model number

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It does not have a model number other thasn Chronotherm IV Plus.

Sorry I can be of no help without the exact model number but somewhere on the back side of the thermostat or subbase is a model number. They do not make them without it. Good luck.

OK... I see numbers on the back of the thermostat... T8601D2019 and 0413 onm the back.. The subbase has the numbers 32207415 and 0413. I didn't think they looked like model numbers.

Your thermostat manual
See page 11 under SYMPTOM (Display will not come on)

http://customer.honeywell.com/techli...0s/69-1410.pdf

Just happened to me. Lifted the cover off (bottom first!), replaced the three double-A batteries, and voilà!

How should the wires be hooked up if I have separate air conditioning and heat? I have the blue wire attached to the rc screw. Nothing attached to the O screw. I have the red white yellow and green attached. Which one are for the air conditioner? The air conditioner is not working.