Honeywell Thermostat Flashing Cool On: The 5-Minute Delay

On a Honeywell Home RTH111, a flashing Cool On message can mean the thermostat is protecting the compressor from restarting too soon. Resideo specifies a five-minute wait in the RTH111 owner’s manual. During that interval, leave the control alone rather than switching it off and on to hurry it along.

This timing belongs to the named thermostat. Honeywell Home is a product family, so first confirm the model printed on the control or its documentation.

Check the cooling request once

Set the RTH111 system switch to Cool and select a temperature below the displayed room temperature. Resideo includes those checks in its cooling troubleshooting section. Then allow the protection delay to finish without making more changes.

If the message stops flashing, check the result at the vents and in the room. The indoor fan can run while the outdoor unit sits idle, so check both. Note whether the air is moving, whether it begins cooling and whether the thermostat still calls for cooling.

What if it keeps flashing?

Persistent or repeatedly returning delay behavior deserves a closer look. Record whether power was interrupted or a breaker tripped before it began. The message doesn’t say what’s wrong, only that the thermostat is waiting.

A blank display is a different problem. The same RTH111 manual includes battery checks, but batteries aren’t the first fix for a readable flashing message. Use the manual for your model, not battery or reset steps from another thermostat.

Stop resetting and preserve the symptom

Avoid repeated breaker cycling. If cooling does not start after the normal delay and settings checks, contact BAHS with the model and a photo of the display. Mention any tripped breaker or loss of power. The $99 diagnostic visit is credited toward an approved repair; testing determines whether the issue is in the control, its power supply or the HVAC equipment.

Key takeaways

• The RTH111 manual specifies a five-minute compressor restart delay.
• A delay that ends without cooling needs a separate equipment check.

Related questions

Need help with your system? Call (925) 999-4095 or book a visit. Repair diagnostics are $99, credited toward the repair. Installation assessments are free.

Written by Andrew Kuznetsov. Andrew is the founder and owner of Bay Area HVAC Service (ADRIUM Service Solutions). He holds a California Contractor License (CSLB #1136642), EPA Section 608 Universal certification, and is factory-trained on Daikin (Houston, 2025) and Mitsubishi. He writes from direct field experience, not marketing copy.

Further reading

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• Choosing a controller for your Mitsubishi system , Handheld remote, MHK2, wired control or the Comfort app: what to check before adding a controller to a Mitsubishi indoor unit.
• Mitsubishi heat pump lineup: which family fits your home? , Compare FX, GX, JX, HX and WX wall units, SUZ indoor styles and P-Series, then decide between a single-zone system and a multi-zone layout.