Hello, I have a 1993 Chevy C1500 pickup. The problem is with the climate control. After the truck has been running for more than a few minutes the air stops coming out of the vents. Regardless of the setting on the dashboard controls, set to hot or cold, set to dash, floor or defrost… no air comes out of the dash vents, defrost or floor vent. You can hear the blower fan running full speed… but no air comes out anywhere.

Once the truck has been off for awhile everything works again for a short time.

I replaced the climate control dashboard unit, and nothing changed. Any ideas?

A maybe for this: Look for a vacuum ball (plastic) underhood which is there to store vacuum for various controls and when there is a break there or any vacuum lines most systems default to defrost but perhaps it could stop the whole show like you are experiencing,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

There are no vacuum lines involved with this system. It is entirely electrical. I just spent a couple of hour under the dash, and as luck would have it, I could not duplicate the problem.

I have noticed that when this problem is occurring there is a VERY small amount of air coming out of the selected vent. So I believe the problem may involve the hot/cold or fresh/recirculate air baffles.

To further confuse this issue… Over the last several days I have found that if I switch every few minutes between the Defrost button, and the Re-circulate button, (which by default has the air coming from the dashboard vents)… The system will continue to operate as it should.

However, if I forget and leave the system on defrost, all air coming out of the system stops... Although the fan motor keeps running at full speed.