Answer
Jan 05, 2026 - 05:22 PM
If the CCC thermostat was working, then it sat for a couple weeks and now it’s totally dead, the most common causes are:
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No 12V power to the thermostat/control circuit (even if “a fuse” looks OK)
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Bad/loose RJ-11 cable or jack (those plugs are fragile and pins get bent)
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Failed CCC thermostat itself (internal failure is common)
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Failed control board (“green panel”) in the AC/heat system (possible, but not the first thing I’d blame)
Do these checks in this order (fastest to prove the problem)
1) Confirm the RV has 12V DC power, not just shore power
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Make sure the coach battery disconnect is ON.
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Confirm lights, fans, water pump have normal strength.
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If lights are dim or the battery is low, the CCC can act dead.
2) Check the RIGHT fuses (not just one)
There are usually multiple fuse points involved:
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Main 12V fuse panel: look for “A/C”, “Thermostat”, “Furnace”, “HVAC”, “Control”.
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Inline fuse near the A/C control box (sometimes behind the return air grill or in a ceiling plenum).
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Furnace fuse (some CCC systems route through furnace control power).
If they “checked a fuse,” odds are it wasn’t the one that actually feeds the control circuit.
3) Reset the system properly
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Turn 12V OFF to the HVAC system: pull the HVAC/thermostat fuse or turn off battery disconnect.
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Wait 2 minutes.
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Restore 12V.
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Try thermostat again.
A lot of CCC systems need a hard reset after power interruptions.
4) Inspect the phone-cord plug and cable closely
Unplug the RJ-11 and look for:
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Bent pins in the wall jack
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Corrosion/greenish tint
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A broken clip (plug doesn’t “click” tight)
Then plug it back in firmly. If the plug is loose, the thermostat will be dead.
If they have a spare phone cable: swap it in. A bad cable is common.
5) Verify if the “green panel” has power
If they can access the CCC control module (often inside the A/C return air area):
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Look for a small control box with LEDs (depends on model).
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If there are no lights and no response, it may not be getting 12V.
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If it has lights but no thermostat operation, then the thermostat/cable is more suspect.
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