Htr/Def-Sometimes no blow!
 

Sometimes when I turn on the heater or defroster you can hear the blower blowing like crazy but nothing comes from the vents. Then maybe later that day or the next time I fire it up, Everything works OK. Any thoughts before I start tearin into the dash?

Vacume leak or blending door or one of the vacume activated servos. A vacume line goes from vacume pump to the back of the heater/ac switch.

From there it is distributed to a few servos behind the dash, the various servos are activated by the various hoses behind the switch. The servos are what actually moves the little flapper doors that direct air flow.

The first thing I would check is the vacume line going to the switch. Start at the pump and check all along that. It leads to the firewall. It then branches off and is hidden behind the hood to firewall seal. That seal comes off rather easy, then you can see the hoses.

After that, it goes thru the firewall to the switch. Check the switch for loose hoses or leaks. The hoses are color coded for the various functions, sorry don't have that info in front of me. Could pull a vacume on those hoses to see if your doors operate properly.

The blending door can be reached by dropping the blower motor and reaching up in there. Sometimes they stick. If the servo is toast, then your pulling the dash.

Usually the servo that fails is located on or near the tranny hump, by the drivers foot/gas pedal. But that is usually the earlier models (like mine).

Sorry, typed as fast as I could, trick or treaters are on their way.

Thanx much,460, its a lot easier when I have some idea of what to look for.