Not getting defrost

[Red 83]

Ever since I bought my '83 C10 Scottsdale I have noticed that is has weak defrost flow. It didn't really bother me too much until winter finally decided to show up this week. Now it takes forever to clear the fog/frost off the windshield. I have the fan control on HI and it sounds like it's working, but very little flow. Also, when the switch is over on defrost, the heater is on more than the defrost is. The bottom half (the metal part) of the dash gets pretty warm. Any ideas?

[bake74]

       Since you said the dash (metal) gets pretty warm, 2 thoughts pop into my head. 
     #1: The ducting under your dash going to defrost has come loose/off, or has been ripped allowing the heat to escape to that part of the dash.
     #2:  Either the controller mechanism for defrost ( which switches it from heat to defrost), has been loosened to where it is not fully engaging defrost mode, or the shutter/control on the passenger side floor board area is not fully switching into defrost mode.

[ehjorten]

Probably: 1) Defrost door not functioning properly.  Check the operation by removing the bottom floor deflector and operating the controls between defrost and heat.  You should be able to feel up inside, the door pivoting up and down.  If not, check the vacuum pod on the side of the heater box that controls it.

2) if it is operating properly, the foam seal that is stapled onto the end of the door might be totally shot!  You would have to remove the entire heater box on the cabin side to repair it.

3) The ducting from the heater box to the defrost never fit tight on any of these trucks!  It sort of just hovers above the opening.  There is a screw and plastic tab that sort of holds the duct over the opening, but from truck to truck the gap can vary quite a lot.  Check to see that your defrost duct is in good repair and that the gap is not gigantic or that part of the duct isn't broken away.

4) Your blend air/diverter doors might not be operating properly.  A typical problem is that the link between the two can separate.  Usually it is the small plastic piece that is bolted to the blend door that breaks or the rivet fails.  You can check the operation of the diverter door with the small plastic piece that routes air to the dash removed.  It is bolted onto the front of the heater box with 3 screws I believe.  Part of it sticks out just below the bottom of the metal dash.

[Red 83]

Awsome, thanks guys!

Probably: 1) Defrost door not functioning properly.  Check the operation by removing the bottom floor deflector and operating the controls between defrost and heat.  You should be able to feel up inside, the door pivoting up and down.  If not, check the vacuum pod on the side of the heater box that controls it.

Where is the vacuum pod located (in the engine compartment, or under the dash)?

[Donut]

I believe the pod is located on the side of the heater box, under the dash, near the gas pedal.
Check your vacuum lines.  This "pod" is vacuum actuated.

[ehjorten]

Donut is correct.  MMMMM....Dough...nuts! 

[Donut]

Hmm, thought I posted again last night.  Oh well,

AC or not?  I think the heat only was still cable actuated.  I may be wrong though...

[whargis]

I'm new here (first post) but I'd thought I'd say a few things as I just spent last week fixing my "no Defrost" issue.  There were a slew of things that were wrong.  I have an 86 with AC so I'm unsure how different things might operate - mine is vacuum operated - and if you have AC I believe yours is as well.  I noticed that my vacuum lines were not connected to the vacuum pod very well so I used some electric tape around the nozzle of the pod - might check that first before you remove the housing.  Also need to check all the vacuum hoses inside the engine compartment, some of these might have come loose - or developed a crack and therefore none of your vacuum lines were working very well.  If you are unsure of what I'm talking about I can post a few pictures (I take a ton of pictures before I work on anything so I can remember how to reinstall everything).  I also agree it's a good idea to check all the connections inside you're dash as well.  Doing these items first will save you some time if this happens to be the issue...  If these items are in order then you might have to remove the housing and replace the vacuum pods (this can be a little tricky)... 

[bake74]

I'm new here (first post) but I'd thought I'd say a few things as I just spent last week fixing my "no Defrost" issue.  There were a slew of things that were wrong.  I have an 86 with AC so I'm unsure how different things might operate - mine is vacuum operated - and if you have AC I believe yours is as well.  I noticed that my vacuum lines were not connected to the vacuum pod very well so I used some electric tape around the nozzle of the pod - might check that first before you remove the housing.  Also need to check all the vacuum hoses inside the engine compartment, some of these might have come loose - or developed a crack and therefore none of your vacuum lines were working very well.  If you are unsure of what I'm talking about I can post a few pictures (I take a ton of pictures before I work on anything so I can remember how to reinstall everything).  I also agree it's a good idea to check all the connections inside you're dash as well.  Doing these items first will save you some time if this happens to be the issue...  If these items are in order then you might have to remove the housing and replace the vacuum pods (this can be a little tricky)...

     Welcome to the site whargis.  Sounds like you had to go a round or two with your heater also.

[whargis]

bake74 - thank you...  Yes, it has been an interesting battle with my heater.  The good news is I'm redoing my interior so I had my dash and everything else removed so it made access to those little things that much easier.  Now I have a strong heater - just need to get the AC up and running and things would be perfect.