HVAC blower cycles on-and-off

MNjeep

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Original poster
Joined
May 24, 2025
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Location
Minnesota
HVAC heater AC blower works intermittently on high and cycles on and off every few seconds. I searched the forums but didn’t see this issue anywhere. Cycles off and on again. Blower fan switch, hot/cold dial, and heat/AC selector switch replaced with Amazon controls. Blower resister also swapped out. Swapped horn relay with hvac relay in distribution box. No changes. Any thoughts on why the blower is cycling on and off?
 
HVAC heater AC blower works intermittently on high and cycles on and off every few seconds. I searched the forums but didn’t see this issue anywhere. Cycles off and on again. Blower fan switch, hot/cold dial, and heat/AC selector switch replaced with Amazon controls. Blower resister also swapped out. Swapped horn relay with hvac relay in distribution box. No changes. Any thoughts on why the blower is cycling on and off?

Check for any damaged or loose wiring connections to the blower motor and the related controls. A short or intermittent connection could cause the blower to behave erratically. Also check the ground connections. This can sometimes be tricky to track down but it's worth checking into.

Even though you've replaced the resistor and switches, the blower motor itself might be faulty. Sometimes, if the motor is nearing the end of its life, it can exhibit on-and-off cycling. This is something to consider given the age of these vehicles.

If there are any vacuum leaks in the system, they could affect the operation of the HVAC controls as well. This is a very common problem on TJs.