1999 Chevy Silverado Noise

1999 CHEVROLET SILVERADO
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R TIPTON
Heater problem
1999 Chevy Silverado V8

My heater makes a knocking noise when the heater is switched from inside air circulation to outside air and heater to air conditioner. On one the noise is a knocking noise in the right side near the dash and in the other is a grinding noise. It stops and starts after a minute or so and last a few seconds.
Jan 5, 2010 at 6:54 PM
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JACOBANDNICKOLAS
  • ✓ASE Certified Mechanic
  • 110,193 POSTS
  • ASE Certified Mechanic
Check under the dash on the passanger side. You will see a vacuum hose going to a vacuum actuator. Unplug the vacuum hose and plug it and see if the noise goes away.

Let me know what you find.

Joe
Jan 7, 2010 at 8:12 PM
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