Possible Clues:

• Fans can be unreliable in their enthusiasm
• Be inconsistent, or what an HVAC unit can do
• Unpredictably, swing a punch, then a couple of taps
• Waver, as will the sirocco and mistral?
• Be inconsistent, with both a powerful stroke and taps
• Change opinions, hit with a pair of taps?
• Pipe to be attached to the two taps? Can't make a decision
• Disappointment with extremes of temperature? Be ambivalent
• Vacillate
• Pipe to be attached to both taps? Can't decide