AC cycles 1x then drops off at highway speed. Under 45 MPH works great. on 2001 Honda Civic

Civic EX /5-stick /177K mi. Q: At Hwy speeds the AC cycles 1x then drops off & blows hot & moist. Under 45 MPH works great (inc stationary). Honda mech's have replicated the problem but can't determine the cause. So far the thermal protector has been replaced, & overall system checked out, but problem persists. The car has been properly maintained, everything else works great, no codes. back w/Honda dealer, 1wk and counting...

by in Lebanon, OH on June 10, 2010
1 answer 1 comment
ANSWER by on June 10, 2010
Check the Throttle Position Sensor. This may sound wacky but hear me out, the A/C is designed to cut off at about 1/2 to full throttle, so if the Throttle Position Sensor has a worn spot, at steady cruise speeds it can go 'open' which makes the engine think that the driver wants full throttle, then the A/C system is shut off, to give more power. I have seen this before on other types of cars.
COMMENT by on June 17, 2010
Thanks for the feedback. Shortly after your response Honda called stating they had again replicated the problem, and inspected the car while running w/problem engaged. Discovered the AC clutch was culprit and replaced. I've had the car back 5 days and it seems to be fixed. To their credit, Honda ate the cost of this second fix.