[1998zq8s10]

Sorry would have searched but need to head to work dont have time right now if any of you guys could help id appreciate it. Im Having problems with my trucks heater/ac. The temp control switch is only switching temps half the time. Sometimes it will work sometimes it wont. I can turn it back and forth from hot to cold and it will not change the temp coming out of the vents. Its random, sometimes just playing with it for awhile will get it to work. Any idea what it could be? Hoping its just the switch. It sucks with KC weather the way it is right now cold in the morning hot in the afternoon!

 

[1998zq8s10]

i replaced the switch that didnt work. I am thinking it is the blend door actuator, i think its electronically controlled in a 98. Any one have any info on replacing it, searched and couldnt find anything that was really helpful.

 

[2000_Diamond]

I am having the same issue, it would work every once in a while and the other day it just stopped altogether, didn't think it was a heater core since i don't smell anything and the carpet is dry, but i would guess that the electronics in that door are probably more expensive and just as much of a pain to replace, i don't even know where to start looking to see if thats it.

 

[1998zq8s10]

in the engine bay, there is a plate on the black box that the a/c lines run into, has a 4 wire plug coming out of it. take this plate off and you can see the blend door. all you have to do is switch the vent back and forth between hot and cold and see if the door moves. if it does your good. if not, its either the switch or the actuator. I just need to know if there is any way at all to replace it without pulling the dash, and how difficult it is to pull the dash if necessary.

 

[gump2388]

mines doing the same thing. seem like if i cut the truck off sitting still i can change it from hot to cold as long as i have the key on. it will go to hot but it wont come to cold. please update this

 

[gump2388]

does anyone know where i can get all the stuff to fix it. i wanna change my vacuum lines too while im at it.

 

[gump2388]

ok hes the deal on this. i checked into mine and there are little gears in the actuator. they call this a air door actuator and the part number for it is 89018356 my chevrolet place had it in stock and he said they fail often. but his part works from 1996-2006 yukons trucks and everything chevy made. im getting ready to tear my dash apart and fix mine. ill keep u updated.

 

[2000_Diamond]

Did the actuator fix your problem? I get no heat all, i am assuming the switch works since if i have it on AC and use the temperature control the fan slows down when it hits 72 or whatever i have it set to, flipping it to heat the air temp is the same. Heading to advance auto shortly hopefully they have it in stock

 

[gump2388]

yep fixed it. ur gears might be striped out in the thing. mine was. everyone i talked to said that its common for them to fail. idk

 

[2000_Diamond]

How hard was it to replace and what did the dealer charge ya for it, mine is asking about $60

 

[jhays]

How hard was it to replace and what did the dealer charge ya for it, mine is asking about $60

i also im askin, mines doing the same thing everything else seems fine, i just dont get hot air, how hard was it to replace? do u have to take out ur whole dash or can u fix it from the engine bay where that other guy said to take the plate off on top of a/c box?thanks guys

 

[MrPab911]

How do you get to the actuator? anyone have a quick guide?

 

[morpheousman]

Update please. How hard is it to replace. How much of the dash needs to come out to reach it?

 

[morpheousman]

I found these instructions for a 98 s10 blazer.

1. Disconnect battery cable.
2. Open glove compartment, and lift tab in upper left corner to allow the glovebox to swing down completely towards the passenger floorboard.
3. Gently remove the line that enters the "Vac Unit", and then the "Vac Unit" itself by wiggling it upwards off its mount. Once removed gently swing it towards the drivers side and out of your way.
4. You now have access to the Temp Actuator.
5. Carefully remove the electrical connector that feeds the Actuator.
6. Using a 1/4" drive wratchet, and 7/32" socket, remove the two (2) mounting screws. (HELPFUL HINT: For maximum ammount of clearance, Keep the wratchect handle facing the drivers side when putting it in place.)
7. There is no screw on the back mounting post, just a pin that holds it steady.
8. Once you've removed the screws you may need to gently pry the Actuator up off the blend door with a screwdriver.
Installation is reverse of the Removal. The Blend Door and Actuator are both keyed, so theres only one way to put it in. Guide the Actuator onto the Door, then re-secure the mounting screws.

 

[DevilDogDiesel]

I have the same problem, no heat. I have back flushed and changed coolant 2 times. On the second try I was able to unplug the heater core. I have changed the t-stat. I just pulled the blend door actuator. Once removed I plugged it back in to see if it moved when I change the temp and it does. I can move the blend door by hand but its a pretty bulky piece. Maybe the actuator just dont have enough umph to move it. Any Ideas? I hate to throw a $60 part at it that wont fix it. I cant think of ANYTHING else it could be!! Any help is appreciated!

 

[davelallen]

How do you get to the actuator? anyone have a quick guide?

x2

 

[DevilDogDiesel]

read post 14. it tells you exactly what to do.

 

[davelallen]

read post 14. it tells you exactly what to do.

Yeah but that's a 98 blazer aren't the dashes different than a pic-up and mine's a 97 without ac

 

[five_oh_407]

Thank you for these instructions, they work exactly as mentioned to get to the blend door actuator. But I don't think that is the cause of my problem, just one of the casualties. A brief note of my situation, I have a 98 s-10 pickup. When I got it two weeks ago, I first noticed the a/c didn't work, I could not differentiate between hot and cold air, but all of the vent settings worked. After about a week, it started blowing hot air out of the floor vents all on it's own with the vent setting know turned "off", nothing was turned on at all. After this happened, I lost any control of the vent settings knob that I previously had. This happened the day I took it to the local chevy dealer to have it looked at. Of course, they did a bunch of stuff that didn't fix the problem and charged me for it. After reading this forum, I yanked the blend door actuator and discovered that this unit only switches the door between hot and cold air, it does not switch between the different vent settings. I put the electrical plug back into the actuator and started the truck to operate the hvac controls and the actuator did not move at all. I also noticed that the vent control knob is vacuum controlled, and the a/c compressor kicks in when the knob is turned to max a/c, a/c, defrost/floor, and defrost. I am now thinking that it may be a vacuum problem. Would I be correct in thinking this and, if so, would the problem maybe lay in the switch itself or the vacuum source that feeds the knob? Any ideas on where the vacuum source comes into the dash to feed the vacuum lines that go to the control knob?

 

[shuriken]

My truck is not the same as yours, so not sure if this is any help but...

I have an 02 S-10 ZR2. Just noticed the heater does not work. Butt cold here so took it in for a diagnosis. Dealer checked once before and couldn't find anything wrong, so I told them the following, this time:
- engine heats up to normal half way temp
- A/C works
- when selecting heat, only lukewarm air enters the cabin
- when selecting cold, cold air enters
- trying to select vent / def / etc. settings has no effect (stuck on vent)

The shop came back and told me that there is a switch that is mounted under the vehicle, (I think they said on the transfer case), which receives vacuum and routes it through vacuum tubes up into the dash through a series of other switches/actuators. It failed (ruptured diaphragm) and allowed oil to be sucked into the vacuum lines. This oil caused the switches/actuators inline to also fail. They also mentioned heater control head problems as a result, I believe (sorry, going from memory). I could hear a hissing sound from the dash behind the heater controls....

They quoted me $1200 bucks. This would cover actuators and switches and labor. They would blow out/clean the vacuum lines and then replace the electrics.

They said for $300 they could maybe get just the heat to blow hot air but the vent selector would still not work. Is this a problem that you guys with earlier model trucks might be having?