A/C goes to default(defrost) upon high load(acceleration). Seen where it's a vacuum leak or accumulation tank/check valve. Replaced accum tank and no change. Upon further investigation realized that with fan off and AC/heater sector to off, if I change the temperature control from cold to hot doesn't blow but temperature changes (blows lightly). I have checked vacuum under hood and can't find a leak. Blend door doesn't make clicking noise like broken.
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Tuesday, June 16th, 2020 AT 6:44 AM
7 Replies
ASEMASTER6371
MECHANIC
52,797 POSTS
Good morning,
I attached a diagram for you.
There is a check valve that prevents the loss of the vacuum on acceleration.
Check that valve.
Roy
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Tuesday, June 16th, 2020 AT 7:02 AM
CWZRD1
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How do you check it when it's in the accumulation tank?
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Tuesday, June 16th, 2020 AT 7:30 AM
ASEMASTER6371
MECHANIC
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With the engine off, there should still be a vacuum in the tank to move the modes in the truck. It should not bleed-off.