1997 GMC Sonoma - Everything coming out defroster?

N

nick

New member
Joined
Apr 7, 2009
Messages
12
Reaction score
0
Points
0
No matter what I turn the heat/air on it comes out the defroster vent. Nothing comes out the vents on the dash and nothing comes out for the floor. Everything comes out the defroster. The heat comes out the defroster. The air (which isn't cold) comes out the defroster. The defroster comes out the defroster. I would really like to know what might be the problem! Thanks.
 
their are some flaps that are not closing or opening to control the flow of air.
 
I am not sure which control system the sonoma uses it is either
vaccuum or cable
so either a control cable has disconnected
or a vaccum pod is lost its vaccuum
or one of your "door actuators" is stuck (vent doors)
good luck
 
nick said:
No matter what I turn the heat/air on it comes out the defroster vent. Nothing comes out the vents on the dash and nothing comes out for the floor. Everything comes out the defroster. The heat comes out the defroster. The air (which isn't cold) comes out the defroster. The defroster comes out the defroster. I would really like to know what might be the problem! Thanks.
Click to expand...

The vent actuator is vacuum controled. The switch it self is like a valve and may have gone bad or just dirty, inspect the switch in the dash and inspect the vacuum line on the drivers side by the brake booster. There are vacuum line's there and it's common for the line to have a leak where the T connections are.

Good luck and keep me posted, be glad to help you get your vent switch working again soon. This is more common with the 4X4 Jimmy's/Blazer's, and Sonoma/S10 due to a faulty 4x4 vacuum switch on the transfer-case leaking transmission fluid in to the vacuum system.
 
Hi, I am new this forum and I love it! I just bought 2000 GMC sonoma SLT with cab.
I bought it last week of october, 2010. one day, I drove and outside was cold. I turn heat on and I noticed that defost won't work and floor vent too. just blow out from dash vent. Until I read this page and I checked my truck I saw that vacuum hose was very rotten and cracked. I replaced new vacuum hose from vacuum manifold to "t" and from T to climate control panel and amazing! it is working perfect wow but one problem is Vacuum manifold to "T" one go to control panel and other one hose to where? Hope to hear from y'all soon.
 
This seems to be a common problem. I too have air coming from the front vent no matter what i do. Yesterday I dropped panel under the driver side and manually pushed on the flaps and they seemed to work ok.
I then found the black line ( vacuum line ) and it measured no vacuum. So I know that is my problem, however I can not trace that line back in the engine compartment. Where is that line going too? Anyone knows of a diagram that i could look at ? BTW my is a 2002 sonoma SLS thank you
 
Here is another comon problem with these tks that are 4x4.
There is a vacuum switch on the tranfercase that goes bad. It gets it's vacuum from the same place your heater does (the vacuum t) So what happens is the tranfercase switch go bad and lets the tranfercase fluid go up in to the vacuum system.then it gets in to your heater controls. what happens when oil and rubber meet... bad things. If caught early you will only need a heater control head and a new tranfercase switch. If left alone for a while you will need ALL vacuum lines , vacuum actuators and heater control head and a switch. This is a very comon problem (GM had a tsb on this for a lot of years)

so if you have a 4x4 pull the vacuum line of the tranfercase and see if it has fluid in it.
 
happy 2011 said:
Here is another comon problem with these tks that are 4x4.
There is a vacuum switch on the tranfercase that goes bad. It gets it's vacuum from the same place your heater does (the vacuum t) So what happens is the tranfercase switch go bad and lets the tranfercase fluid go up in to the vacuum system.then it gets in to your heater controls. what happens when oil and rubber meet... bad things. If caught early you will only need a heater control head and a new tranfercase switch. If left alone for a while you will need ALL vacuum lines , vacuum actuators and heater control head and a switch. This is a very comon problem (GM had a tsb on this for a lot of years)

so if you have a 4x4 pull the vacuum line of the tranfercase and see if it has fluid in it.
Click to expand...

My gmc is not 4x4 and here pix2000 gmc vaccum.webp

One go to control climate and where other go to ?
 
drtgmc2000 said:
My gmc is not 4x4 and here pixView attachment 104
One go to control climate and where other go to ?
Click to expand...
It goes to a vacuum container.
If you reach in and touch the T, move your finger straight toward the fender.
Just below the bracket holding the anti-lock controller is a plastic vacuum container mounted flush into the fender inner wall. A plastic tube should be sticking out just below the bracket to push the rubber tube onto.
 
Last edited:
multiple posts for some unknown reason
 
Last edited:
lmleck said:
It goes to a vacuum container.
If you reach in and touch the T, move your finger straight toward the fender.
Just below the bracket holding the anti-lock controller is a plastic vacuum container mounted flush into the fender inner wall. A plastic tube should be sticking out just below the bracket to push the rubber tube onto.
Click to expand...

Yes, I found and I connected and One more tube go to where?
see picture that I already connected one tube to plastic vacuum container
and One more tube that I put screw. where suppose to go to ?
 

Attachments

  • 2000 gmc vaccum-1.webp
    2000 gmc vaccum-1.webp
    70.6 KB · Views: 168
  • 2000 gmc vaccum-3.webp
    2000 gmc vaccum-3.webp
    69.8 KB · Views: 189
  • 2000 gmc vaccum-4.webp
    2000 gmc vaccum-4.webp
    76.4 KB · Views: 163
This is photo of mine. 03 sonoma
I labeled each hose.
MVC-001S.jpg
 
Is vacuum storage between fender? If so, I have to take anitlock off and take black ( vacuum storage) off to find tube?
 
drtgmc2000 said:
Is vacuum storage between fender? If so, I have to take anitlock off and take black ( vacuum storage) off to find tube?
Click to expand...

It is just about 1 inch plastic tube sticking out from side of vacuum storage container, unless it has been broken off.
Look at picture. The plastic tube is just under edge of antilock bracket.
 
The plastic tube is just under edge of antilock bracket.
you mean, we have two plastic tubes at same place? one for heater knob and one for vacuum storage?

I connected heater knob to plastic tube is under edge of antilock bracket.
 
You must log in or register to reply here.

Share this page



Back
Top