ok, up until thurs. air flow/heat /cold all good. no floor heat though....so i cut hole in "plenum" were the door is that controls heat to floor. all went well got it all back together tested movement on all switch postions, all good. then noticed air flow/volume was gone!!!! the switch moves freely and i can hear the blower motor going up and down in speed. switched from ac to heat no dif. did notice that the bigger door behind glove box opens and closes well. i did blow fuse in box under hood when i checked the connection at blower motor. that is the only thing that went "wrong" but swapped it out and still no fix.

i have spent the day on the forum and no clear answers, all i found is that i am not only one to have this problem but found no fixes.
my closest guess is to check the relay i guess, but after reading the threads that doesnt seem to be the problem given that the motor and switch respond correctly just the air volume is gone from all positions.

the only other thing i found is that another door has a broken connection (see pic). no not my blazer just to show other issue.

any help would be greatly appreciated....i have to bundle up to drive and go outdoors.

thanks

 

Schematics of the HVAC system in your truck have been posted in the past (I posted them). Here they are again for your viewing pleasure:

98+ HVAC Schematic

You have a door hanging up somewhere in there. There really is only one door that can have this kind of an impact on the air flow and that is the Mode door (moved by the Mode Actuator and the Slave Mode Actuator).

 

thank you for posting the schematic. so after looking at the schematic, would i be correct in guessing that the door that broke in the pic i posted is the mode door. i think so because i noticed that it has a grey vac. line that is part of a "y" connection coming off the yellow vac. line - just inside the dash compartment.
and after looking at the sch. that seems to be the case. the acuators all move just fine, its just the one in the pic that is broken.

so it looks like my attempt to take the easy route is not going to pay off after all.

i just dont understand why/if what i did could jam and break the door on other side of plenum space.

thank you for schematic.

 

The gray line runs to the slave mode actuator. It should 'T' into the yellow line to the pull side of the mode actuator. The push side of the mode actuator should be a brown line.

 

just a quick question before i going tearing things up.
if the brown vac. line became disconnected would the grey vac. line push the door hard enough to snap that connector?
i just ask out of curiosity. to my knowledge the connection was not broke before i started monkeying around

 

It should not have sufficient force to break anything.

 

ok, then i need to do a full tear down to find the blockage.
i tried to turn the door by hand and it will only move about a 1/4" and after watching the grey line acuator move, that is def. not enough movement.

just have to find the blockage then.

thank you again.

 

ok, sooooo...i replaced connector from actuator with grey vac. line...door was off hinge point at bottom causing the snapped connector, but having fixed that did not fix the main problem.

i traced all the lines they are connected and doors are all moving now.
still no pressure, i am starting to think there is a jamb somewhere on blower motor end of things.
(no i have not removed the dash to do this...you dont want to know)

the door that moves by elec. motor/sensor at top right of plenum is working as well (air temp door)
vac. yellow/brown connected and moving
vac. red/blue connected and moving
vac. gray connected and moving now
everything responds to the hvac panel controls as well.

the only thing i can think to do is take blower motor out of housing and check for jamb in there.

when the orange (recirc) opens i can see the fan/blower moving and it responds to the speed controller on hvac panel.

i know i am repeating myself, just dont know where to look.

 

ok the pic has what i have replaced.

sorry if i screw up the component names.

 

ok, problem solved ...there was a bunch of debris blocking up the system.

just in time....5 degrees is cold.