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No heat/air/vent control issues? Start here GenII

52K views 60 replies 24 participants last post by  The GOZ 
#1 ·
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#7 ·
Jasen said:
Wait, isn't GenI cable operated :confused:
Not my 89. Heater AC box doors and baffles are vacuum. Heater control valve (the plastic tree) is present and vacuum opereated BUT in my year, it doesn't control flow of water to the front heater core. It only allows hot water to flow or not flow to the rear compartment heater core. Hot water (in the stock arrangement) is always flowing to the heater box.

But I still like the purty colors.

Lump
 
#8 ·
The diagrams I found for 89-90 aren't as nice and clear cut as the other, but I'll sort it out.
What colors would you like me to use.
 
#10 ·
Lumpy, I've googled my brains to mush today. I've have tried every search criteria I could think of and some I couldn't think of. I would think the system works about the same as a GenII, but I can't find anything on how/where the vac lines run. This is probably the clearest thing I've found, but the banana head left out the water control valve vacuum circuit.

Image uploading. Refresh page to view
 
#11 ·
That's the thing. There is no water control valve in my 89. Just for the rear heat. The one that goes bad for everyone else isn't present in mine. In stock condition, hot water circulates through the box all the time, even when you're calling for A/C.

Lump
 
#12 ·
Yea, the rear vacuum actuated water control valve, or water on/off valve. I can't find squat on it other then it exists. If I could find out where the vac lines run to from I could put something together.

From the 2,543 crappy pictures and diagrams I looked at today I would glean that it is basically the same set up as a GenII, but is just an on/off set up.
 
#14 ·
Anything for you Lumpmeister :mrgreen:

If you'd ( or any GenI owner) give me a couple three pics of this goes here and then over there, I'd put something together for those people who's HVAC isn't working.
 
#15 ·
Jasen said:
If your not getting heat, your vents aren't working as the should or you have no air flow for front and or rear heat, start here.
This is why I like the internet!

I would never have found the source of my problem without this. After much cussing and almost yoga-like contortion of my hands, I was able to connect a hose to what was left of the plastic straw in front of the throttle body. (I just didn't have the time or inclination to tear open my dash and remove the dog house.) I also replaced most of the other tubing and now my air changes direction as intended. It drives me nuts that GM engineers came up with this kooky scheme of tubes and valves in the first place. I guess it's not unique to GM, but still...

Now, I'm off to find out why my compressor remains comatose...
 
#20 ·
No, it's a flat thing with 4 different-colored vacuum lines running to and from it.On the passenger side of the doghouse (you have to remove the center console but not the doghouse to see/get to it).
 
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#22 ·
So your talking about the hoses/connected to the switch???? Because I have removed the whole dog house without seeing any hoses. Does anyone have a pic of what we are talking about. I'm sure it's easy. It's gonna be 97 today. If there's any chance that I can get this working it would save me n my son.

Thanks in advance
 
#23 ·
Awwww. The hoses were stuffed behind the radio.
Ok so I have the dash open the counsel off and everything looks good. If I turn it on and twist both the fan speed switch and the ac to def switch I get a lil bit of sound as if it was gonna swing into AC/vent mode but no go.

Anything else before I replace the switches ???
 
#26 ·
Dealing with an issue with no defrost. Lucky me, it's December. There are two vacuum operated doors for heat control...one for floor and one for front vent and defrost. My defrost decided it was cheap white plastic and the nub that the actuator connects to decided to break off. The actuator end is metal of course :roll:

Currently trying to figure out if I can get access without damaging the system, but it looks unlikely. The blend door for defrost will fall to panel vents due to its weight and fulcrum, but if it is pushed up it will catch air and stay open as long as the van is on and the air is running. At this point, all I care about is defrost because I never use the panel vents, so I think I'm going to rig up something to keep it open or close to open so that the fan can finish opening it. I'll have to remove the dash to get proper access to it to repair it, which means I'll likely either have to rebuild the control arm thingy or rob one out of another JY Astro, not something I plan to do anytime soon. Took a while to figure it out, but a little listening and a flashlight saved the day..sort of.
 
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