1997 Chevy Astro AC stops blowing out of dash vents at high

MASONC

MEMBER
1997 CHEVROLET ASTRO
6 CYL
2WD
AUTOMATIC
215,000 MILES

The ac in my 97 astro van works fine when I drive around town and on the highway. As soon as I hook my camping trailer to it, the ac works until I hit 50 miles per hour then the air from the vents goes away. I let off the gas and go below 50 it comes back on. Accelerate agian and once I hit 50 the ac stops blowing out of the dash?

Monday, July 26th, 2010 AT 3:40 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

You have a vacuum leak under the dash. The vent doors are actuated by engine vacuum. The added load of the trailer forces the engine to work harder. Thus, intake vacuum is lowered. If there is a slight leak, the lowered intake vacuum and the leak combined allows the air flow to change directions.

Check under the dash. If you are lucky, you will hear a hissing sound with the engine running. If no sound, you have to check visually. Look for cracked, dry rotted lines.

Let me know what you find.

Joe
PLEASE NOTE: Check under the hood for the same type of problem if nothing is found under the dash

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Tuesday, July 27th, 2010 AT 12:08 AM