MercMariner

My girlfriends AC stops blowing when you step on the throttle. As you let off of the throttle it starts blowing again. Is this supposed to happen? Has anyone had this problem before? She said she's never noticed it before I pointed it out.

Bert

If it just switches to the defrost vents, there's a vacuum leak in the HVAC system.

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Bert

MercMariner

You're saying if when the AC stops blowing, it changes to defrost, then back to the regular vents there's a leak? I will double check but I'm fairly certain that it just stops blowing period, then returns as you let off of the gas pedal. I know that older compact cars would shut off the AC as you throttle up to make sure the power is at the motor and not being used on the AC but I assume the 6 cyl can handle the output...

Bert

If the blower itself stops running, then it wouldn't be a vacuum leak.

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Bert

MercMariner

So it's been a while but it does default to the defrost under acceleration so I assume it is a Vac leak. Can anyone point me in the right direction to start checking vac lines?

CatSkinner

Check the seal for the PCV valve and the plugs for the unused ports on the vacuum manifold, commonly overlooked.