98 Blazer No Floor Heat

[TheJuicer]

I have a 98 Blazer 4x4 4.3L with 155,000 mi. I can't get heat to go to the floor. Instead it comes through the defrost vents up top. I did some investigating and confirmed that I do get vacuum coming through the red and blue lines into the actuator(I think that's what it's called) above the gas pedal. So I know it's getting the vacuum. I hear a snapping noise when going from defrost to floor heat using the manual vent control on the dash. I was under the dash watching the linkage as I turn the heat control and it does move but that snapping sound doesn't seem right and it's coming from that actuator near the gas pedal. Am I going in the right direction? I have read some older threads on here and others have referred to the blend door breaking. Any help would be greatly appreciated.

Thanks!

[old_master]

The vacuum actuator you're looking at has 3 positions: Floor, Dash, and defrost. When you move the mode switch to the different positions, you should see the lever move to each of the positions. The diverter door may have broken away from the lever, if that's the case, the entire dash and HVAC housing must be removed and the HVAC housing split apart to repair it. While you're in there, check the temperature blend door and the recirculate door actuators as well. It's not a difficult job, but very time consuming. If it's your first time, plan on it taking most of a day. There's a "How To" in the main Blazer section under heater core replacement. You might want to consider replacing the heater core as long as you're in there too, just as a preventive maintenance measure, (Murphy's law would definitely apply if you didn't replace it).

[TheJuicer]

Thanks for the help. Is there a rule of thumb to tell if it's a broken blend door or the actual actuator? I haven't been able to manually open the door to get floor heat. I heard that's a good check to see if anything is cracked inside. The white plastic arm with the spring also seems quite loose going into the air box. I can move it back and forth with a good amount of movement. Should it be tighter? I do get heat through the dash vents so I know that portion is working. Is the actuator with the yellow vacuum line control something else?

Thanks!

[old_master]

Is this the standard manual HVAC system or is it the optional automatic climate control system? (Two totally different diagnostic procedures.)

[TheJuicer]

It is the manual HVAC system with the controls through a turning nob on the dash.

Thanks,
Justin

[old_master]

In the DEFROST position, the brown vacuum line is the only line that should have manifold vacuum. In the HEAT position, the yellow vacuum line is the only line that should have manifold vacuum. The blue vacuum line should have manifold vacuum in the MAX, NORM, BI-LEV and VENT positions only. The red vacuum line is a vent, (to atmosphere) for the heat/defrost actuator and will have vacuum only when the actuator is switching from one position to another.

[TheJuicer]

I took a look at the how to heater core replacement and didn't read anything on repairing this. I am assuming they aren't the same steps. Do you know of a "how to remove" the HVAC system to get to this lever?

Thanks

[old_master]

To replace the heater core, the HVAC housing must be removed. After the housing is removed, disassemble it and you can access all of the doors and actuators.

[TheJuicer]

So I got the blend door out and it was cracked. I did not remove the dash and HVAC system. I just removed the bottom floor vent panel/console/body control module etc. and since it was cracked I was able to pull it out. I am assuming to put a new one in I do have to take the dash and HVAC system apart. But for now I am trying to come up with a work around without removing everything which I am sure everyone has brainstormed over. With a new blend door can I push the one end through the vent and then the other end snaps in? Or is there not enough play to be able to do that? I read somehwere you have to crack the HVAC housing to put the new one in and then glue it back together?

[bcocca]

I have the same problem with my 98 Jimmy, must run in the family.
Did you have to remove dash to install new door.
bcocca

[DRGREENTHUMB1001]

Yeah me too..looks like a total pain in the ass and a ton of work...why cant they make stuff like this out anything BUT plastic? They spend to much on overpaying Union workers to turn an screw and NOT making quality vehicles. The Japs have labor hour costs that range form $15-$20 dollars an hour LESS and people wonder why GM needed a bialout