My heater quit switching between def. floor etc. It stays on the front dash outlets. I can hear a hissing from behind the dash.


Would my heater control unit be leaking or something else.

1999 S10 Blazer 2 door LS auto 4x4.

 

It definitely sounds like you have a vacuum leak behind the dash. Time to get under there and have a look.

 

I just got it apart it is right at the switch where the vaumn lines connect. Guess I need new heater control thing.
Thanks

 

So the leak is internal to the HVAC control head? If so, then you likely will need to find a replacement, either new or used.

 

I guess it is the control head. I took off the vacumn hose connector it looks ok.

$77.00 Rock auto. Local parts store no can get go to dealer they say.

 

The manual heater control is fairly common. I would check with some junkyards in your area before dropping that kind of money on the part.

 

Anybody that would like to know new heater control assembly fixed the problem. No more hiss at the switch.

 

Glad you got it fixed and thanks for the followup!