TheGoat Posted January 19, 2012 Share Posted January 19, 2012 Subject: 1985 GL 4WD Wagon. As some of you know, I don't know alot about these cars, yet. So as I was driving it the other day, I noticed that no matter which button I pushed on the selector, heat would only come out of the vents. So, immediately I thought, "Must be a vacuum issue." So I pulled her into my garage, fired up the furnace, left the garage, and came back when the garage was nice and toasty (60 F). So I started checking vacuum, checking for missing or cracked hoses, when my brother noticed the manual selector lever on the far lower left part of the dash (labeled something like, "B/L, Vent, Vent Off") so we thought, "Hey let's check the owner's manual. Maybe there's something in there about using this lever for defrost." Lo and behold, in the owner's manual it says to move that lever to "Vents Closed" (paraphrasing here) for the defrost to work. So the car's all nice and warm (not the engine, it hadn't been statrted, but the car itself from sitting in aforementioned toasty garage) now, so I start it up, push the defrost button and move the selector lever to vents closed. Guess what? Defrost works like a charm! Move the lever to "vents", air out of vents, move lever to bottom most position, air comes out at feet - so everything's working as it should, right? Easy fix! Ahh, but not so fast... Move to the next morning. Car's been outside all night, and here in Iowa parts, our brief affair with global warming has ended and it's been getting pretty cold out. So, I start the car, let her warm up for a few and off I go to work. Windshield's getting frosty on the inside so I hit the defrost buttom and make sure the selector lever is where it's supposed to be and...no defrost. Move the selector lever to all the different positions and heat only comes out of the vents. Really? Yes, really. The whole way driving to work, I'm moving that selector, pushing "Defrost", pushing "Heat", pushing "Bi-Level" and nothing changes - heat out of vents only. BUT, as I pull into a spot in my parking garage, the defrost miraculously fires up (after all the button pushing and lever moving, I'd left the lever in the vents closed position and the defrost button selected)! WTF? This morning, same exact thing happened - no defrost until parking garage. And this morning, sitting in the parking garage with the car running, I test the different lever postitions and differnt button selections and all works as it should - switches from defrost to vents to heat, just like it should. I know that at idle I'm probably drawing the most vacuum, so one could say that in the parking garage at idle is giving me just enough vacuum to make everything work properly, but after everything starts working it stays working, while normal driving, until the car cools down. So...it seems that ambient temperature is causing blend door failure...but why? Quote Link to comment Share on other sites More sharing options...
Yo'J Posted January 19, 2012 Share Posted January 19, 2012 That is good and selectively funny! Pun intended. The cable that goes to the selector from to the valve cracks easily I would start there. Its a bicycle type cable that pushes instead of pulls i.e. its solid not braided. In my wagon I have to reach under the dash to push the vent closed to get heat, its just above the gas pedal behind the heat riser. You could have a flap cover cloth thingie flapping around in there too selectively getting in the way. Quote Link to comment Share on other sites More sharing options...
987687 Posted January 19, 2012 Share Posted January 19, 2012 If you park it with the defrost working... does it work in the morning? Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 20, 2012 Author Share Posted January 20, 2012 Nope. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 20, 2012 Share Posted January 20, 2012 I am going with a vac leak someplace. When the car is cold the (most likely a crack in plastic) opens up and no def. When car is warm from a warm garage, the thing expands and closes the leak. STart by checking the blend door motors (vac diaphrams) with a hand held vac pump. Wiggle them while you have the vac pulled on them and see if the needle moves. Also test the vac resivoir under the hood (i think this has one) if it has one. Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 20, 2012 Author Share Posted January 20, 2012 Well, I checked the actuator lever and watched it move the door and it all worked without a hitch. So, maybe it is vacuum... I did test the reservoir for vacuum - have good vacuum there. But you might be right - I'll starting checking for cracked lines; but isn't the blend door manually operated (I have a manual selector on the lower left of the dash)? Quote Link to comment Share on other sites More sharing options...
nipper Posted January 20, 2012 Share Posted January 20, 2012 Well, I checked the actuator lever and watched it move the door and it all worked without a hitch. So, maybe it is vacuum... I did test the reservoir for vacuum - have good vacuum there. But you might be right - I'll starting checking for cracked lines; but isn't the blend door manually operated (I have a manual selector on the lower left of the dash)? Sorry i call them all blend doors sounds better then one of the directional flappy things Quote Link to comment Share on other sites More sharing options...
Dj7291993 Posted January 20, 2012 Share Posted January 20, 2012 In mine, I usually have to get it going, then let off the throttle completely to give it the vacuum to switch it. Works fine when it's warm, but when it's cold, I have to force vacuum, easiest way is to go from WOT to decel 'till it kicks over (usually a second or two). Once it receives the vacuum, it will hold it until something else releases it (like hitting another mode). Try that, see if it works. Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 20, 2012 Author Share Posted January 20, 2012 That's kind of how mine acts. Like this morning, I let it warm up for longer than usual and the defrost worked - until I started driving on the freeway - then it went back to vents only. But when I got off the freeway and stopped at a light - viola! Defrost worked again. So, a vacuum issue, I guess. Glad to know it's not just me having this issue. Quote Link to comment Share on other sites More sharing options...
Dj7291993 Posted January 20, 2012 Share Posted January 20, 2012 That's kind of how mine acts. Like this morning, I let it warm up for longer than usual and the defrost worked - until I started driving on the freeway - then it went back to vents only. But when I got off the freeway and stopped at a light - viola! Defrost worked again. So, a vacuum issue, I guess. Glad to know it's not just me having this issue. I wonder if you have a leaking check valve. Because once you get it there, it should stay. Mine doesn't like to switch, but once it does, it stays. Wish I could find more info on how it works, but I'm not seeing it on Mitchell. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 20, 2012 Share Posted January 20, 2012 I wonder if you have a leaking check valve. Because once you get it there, it should stay. Mine doesn't like to switch, but once it does, it stays. Wish I could find more info on how it works, but I'm not seeing it on Mitchell. That is quite possible too, it is sticking untill the car warms up. Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 21, 2012 Author Share Posted January 21, 2012 Where would I find that?:-\ Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 22, 2012 Author Share Posted January 22, 2012 I'm going to see what kind of vacuum I'm getting while I'm driving it. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 22, 2012 Share Posted January 22, 2012 i don't recall but it looks like a little disk sometimes, lmagine 4 quarters stacked together. Best is to just follow the line between the resevoir and wherever the hose goes to. Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 25, 2012 Author Share Posted January 25, 2012 Well, apparently vacuum isn't the issue: I've 20" @ idle and still no defrost until...well until something happens, I'm not sure what makes it start working. All I know is that it acts much worse the colder the weather is. It's been a little warmer 'round here lately and so it has been working a little better. So, yeah, something seems to be "sticking." Guess I'll trace the lines and see if there's something spliced into the vacuum line that isn't behaving the way it should. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 25, 2012 Share Posted January 25, 2012 Wwhere did you measure that, at the manifold or the output of the vac resivoir? Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 26, 2012 Author Share Posted January 26, 2012 @ The reservoir. Quote Link to comment Share on other sites More sharing options...
Yo'J Posted January 28, 2012 Share Posted January 28, 2012 How about testing it after the solenoid behind the dash, while the engine is running, as you go through the heater settings. If that solenoid has a leak, I'd be suprised but, you would have limited function. On my wagon, the hot coolant goes through the engine to the valve and to the heater coil, at the valve there is two functions that operate together, the door for the mixed air and the coolant valve. The door has too much weight and while driving it opens to mixed air and cuts off the flow, leaving me cool air. The knob that opens that valve is like a bicycle cable but made to push instead of pull, its a solid wire and housing. The wire housing can crack and fail easily leaving you no resistance to keep your dash settings. I'm interested in what you find. Josh Quote Link to comment Share on other sites More sharing options...
TheGoat Posted January 29, 2012 Author Share Posted January 29, 2012 Thanks for the suggestion. I think I'll give that a try. It works pretty good when the weather's above 30 F. Quote Link to comment Share on other sites More sharing options...
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