1999 Chevrolet Astro



January, 12, 2009 AT 8:28 PM

Heater problem
1999 Chevy Astro 6 cyl Two Wheel Drive Automatic 115000 miles

Hi, I have heat now thanks to BlueLightnin's quick thorough response. My son was able to do the job this weekend. Yeah! The problem now is that the heated air only comes out of the defrost's vent by the windshield, no matter what position I put the little dial-dashboard vents, floor vents, combination, etc. Although the lo, med, and hi air output dial works. Anyone out there know what to do? BlueLightnin', are you there?


2 Answers



January, 13, 2009 AT 10:05 PM

This is easy. There is a 6 millimeter black plastic vacuum line that is baked and cracked or seperated under the hood. This has killed your vacuum vent controls because there is no vacuum. On one end, it connects to a vacuum port on the intake manifold just behind the air conditioning compressor, just to the right of the engine intake. It runs under the black rubber flex hose between the air filter and the throttle body. It runs to the left and connects about 4 inches behind the washer fluid reservoir on the left. These bake and crack in half right under the intake black hose everytime. For now, you can find the break and splice it with a one inch peice of weedeater fuel line just plugging each end of the break into each end. Now, on mine, you have to pull the drink holder/glove box and the cowling, but I cut off each end of the line about 3 inches from the end, got a 2 foot piece of heavy wall 8 millimeter air line tubing, and plugged it into each end with a heavy coat of silicone RTV.

Good luck,




January, 16, 2009 AT 1:04 AM

Hello again

Thanks for the donation.

Glad you got your heat working again. It sounds like your blend doors under the dash are not operating. The advice given above by techman1 (above) is great and is probably the culprit here. Inspect the vacuum hoses and ensure they are in good condition and tightened well. Without proper vacuum, the blend door can not operate, which prevents any other vents from having air flow. When something goes wrong with the heating system, the default is to provide air flow to the defrost vent.

Post your results of the vacuum hose inspection and I will follow up as needed.

Hope this helps.
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