Only getting air from the defrost vents...vacuum leak?

[Thrall]

I'm assuming that is the case. I'm not too familiar with how this all works, so does anyone have suggestions on how to check for leaks? Or is there another problem all together?

It's a 98 SR5. The rear heat works fine.

 

[TheDurk]

Do you have the manual or the auto control with the digital readout? (I think SR5's had both in '99, don't know about your year). I don't think either one uses vacuum for any control function. The manuals are all levers, cables and plastic gears (which can strip and jump off their centers) and the autos use electric servos for mix and temp. I'm no expert, but that's how it looked when I went through that part of my FSM.

The autos have a self-diagnostic routine that puts trouble codes on the Temp read-out, probably a bum servo. If it's a manual, just get in there and trace the linkage from the mix control to the mix flap.

 

[gptoy96]

This happened to mine. Turned out it was the heater box. A flap in it broke and couldn't change it's flow to where i wanted it anymore. Rear heater on mine still worked good too.

Turned out to be a pricey fix, had to take a lot of the dash apart to get at it.

 

[cfranck1]

Sounds like what a few others have said. A bad Blend Door Actuator or an actual Blend Door in the Heater box?
If it's manual controls you might luck out and it could be a popped off linkage??