Climate control super-mystery - at least to me....
11-02-2011, 04:39 PM
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Climate control super-mystery - at least to me....
1989 S4
I had the "hot air all the time" problem and when recently changing the light bulb in the climate control module, I noticed one of the plastic cogs had snapped in half.
It was this cog....
Now, as you can see from the pic, the top slider (Temperature) is hooked up that big arm and when you slide the slider, the arm moves and turns that cog.
The cog is attached to a metal post that turns with the cog. I assumed this metal post was the thing that controlled the temperature out of the vents.
I removed the broken cog and turned the metal post all the way to the left - where it should be if the slider was slid to "cold" - voila, no more hot air through the vents. I figured at this point that no matter where I slid the temperature slider, it would now always pump out cold air.
Now, it has been getting more cold out, so I took the climate control module out last night and turned the metal post all the way to the right to get some heat. I get in the car, wait for it to warm up and turn on the fan - cold air comes out. Mind you - the slider was still in the "cold" position; like I said above, I figured it didn't make a difference where it was seeing as the cog was not there anymore.
Wait a bit more and still no hot air, so I slide the slider over to "hot" just for the heck of it and BAM!.....hot air.
So, basically, my temperature control slider seems to be working as it should, but that one cog is completely missing from the equation.
I noticed that the slider for the feet/window/face is not attached to any cogs - it seems to swipe a green board across some tracks (which I cleaned up while in there).
So, what am I missing? What does that cog/metal post even do when you slide the temperature slider left or right???? I'm stumped!!
I had the "hot air all the time" problem and when recently changing the light bulb in the climate control module, I noticed one of the plastic cogs had snapped in half.
It was this cog....
Now, as you can see from the pic, the top slider (Temperature) is hooked up that big arm and when you slide the slider, the arm moves and turns that cog.
The cog is attached to a metal post that turns with the cog. I assumed this metal post was the thing that controlled the temperature out of the vents.
I removed the broken cog and turned the metal post all the way to the left - where it should be if the slider was slid to "cold" - voila, no more hot air through the vents. I figured at this point that no matter where I slid the temperature slider, it would now always pump out cold air.
Now, it has been getting more cold out, so I took the climate control module out last night and turned the metal post all the way to the right to get some heat. I get in the car, wait for it to warm up and turn on the fan - cold air comes out. Mind you - the slider was still in the "cold" position; like I said above, I figured it didn't make a difference where it was seeing as the cog was not there anymore.
Wait a bit more and still no hot air, so I slide the slider over to "hot" just for the heck of it and BAM!.....hot air.
So, basically, my temperature control slider seems to be working as it should, but that one cog is completely missing from the equation.
I noticed that the slider for the feet/window/face is not attached to any cogs - it seems to swipe a green board across some tracks (which I cleaned up while in there).
So, what am I missing? What does that cog/metal post even do when you slide the temperature slider left or right???? I'm stumped!!
11-02-2011, 04:44 PM
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Oh....and there is no light that hits on the inside of the big fan ****, is there? The fan symbol seems like it should light up, but it doesn't.
I could not see any fiber optic cables leading into the area near the **** - there are two cables that fit in holes above and below the **** (lights up the "min" and "max" letters beside the ****), but it doesn't seem there is a way for light to illuminate the fan **** - am I correct?
I could not see any fiber optic cables leading into the area near the **** - there are two cables that fit in holes above and below the **** (lights up the "min" and "max" letters beside the ****), but it doesn't seem there is a way for light to illuminate the fan **** - am I correct?
11-02-2011, 04:54 PM
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Fan control has no light on the **** only on the little window that shows the fan speed.
The temp slider controls 3 things - the potentiometer that sets the desired temperature (the cog & post you mention) and 2 limit switches one at the extreme cold end and one at the extreme hot end.
At the Cold end - it doesn't matter what the temp control says you just get full unconstrained cooling - water valve stays off the bypass flap bypasses the heater core and the mixing flaps fully close. If the AC is on the car will continue to cool to as cold as it can get ..
At the Hot end - it doesn't matter what the temp control says you just get full unconstrained heating - water valve stays open the bypass flap is inactive the mixing flaps fully open & the car will heat up as much as it possibly can...
In between these extremes you get a closed loop temperature control - dependant only only the potentiometer setting. Once the set temperature is reached the system will modulate mixing to maintain that temperature. The sensor loop has to be fully operational for this to work properly.
See update photo below you can see the cold switch in red circle and hot switch in white circle (red operates over a segment - last few mm's of travel
I think this is primarily as a backup system - if for any reason the sensor control loop fails you can overide it and get hot or cold options via the backup
You may have to modulate it manually but at least you won't totally overheat or freeze. The switches generally seem to be reliable.
Alan
I imagine you could successfully repair your broken cog with JB weld for about $6
The temp slider controls 3 things - the potentiometer that sets the desired temperature (the cog & post you mention) and 2 limit switches one at the extreme cold end and one at the extreme hot end.
At the Cold end - it doesn't matter what the temp control says you just get full unconstrained cooling - water valve stays off the bypass flap bypasses the heater core and the mixing flaps fully close. If the AC is on the car will continue to cool to as cold as it can get ..
At the Hot end - it doesn't matter what the temp control says you just get full unconstrained heating - water valve stays open the bypass flap is inactive the mixing flaps fully open & the car will heat up as much as it possibly can...
In between these extremes you get a closed loop temperature control - dependant only only the potentiometer setting. Once the set temperature is reached the system will modulate mixing to maintain that temperature. The sensor loop has to be fully operational for this to work properly.
See update photo below you can see the cold switch in red circle and hot switch in white circle (red operates over a segment - last few mm's of travel
I think this is primarily as a backup system - if for any reason the sensor control loop fails you can overide it and get hot or cold options via the backup
You may have to modulate it manually but at least you won't totally overheat or freeze. The switches generally seem to be reliable.
Alan
I imagine you could successfully repair your broken cog with JB weld for about $6
Last edited by Alan; 11-02-2011 at 05:13 PM.
11-02-2011, 05:31 PM
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Ahhhh - that makes total sense. So, basically, without the cog, I can get extreme hot or extreme cold. 
Now that I think of it, when I slid the slider to the left, I got cold air and would continue to get it until the slider was slid all the way to the right and visa versa; so it was either one or the other.
Seeing as I only drive the car in the summer months (and the odd October/November), I'll just set that metal peg to "cold" and leave it there all summer (until I get a new cog that is).
When the cog broke, it must have been tuned to "kinda, sorta hot", because that is what I was getting out of the vents all the time.
I am certainly happy it's not a temp sensor thing and I don't have to tie the heater valve shut - just a broken piece of plastic.
Also good to know the fan **** doesn't illuminate - when I had the module out, I pulled the two fiber optic cables out of the white square housing that surrounds the fan **** and cut a wee bit off on the plastic shield to expose more of the optic cable and re-installed them - this made the lights brighter all around the fan ****.
One thing I did was pull out that lil' scroll piece that holds the "1,2,3,4" fan speed and cleaned up the clear plastic cover that goes over the number scroll thingy....it was VERY "hazy" - you could barely see the numbers.
Now it is so bright, I can't stop staring at it and now I can see light creeping out at the top and bottom of where the number is.
...oh, and I tried the JB Weld and even tried JB welding two washers on either side of the cog to give it more strength and it worked ok until you slide the temp slider to about the 30% mark - it seems at that point, there is some additional stress put on the cog which makes it slow down a bit and it was at this point every time that it would re-break. I tried adjusting the bigger arm (the copper-colored screw that sits in the middle of the black plastic), but this did not help.
Now that I think of it, when I slid the slider to the left, I got cold air and would continue to get it until the slider was slid all the way to the right and visa versa; so it was either one or the other.
Seeing as I only drive the car in the summer months (and the odd October/November), I'll just set that metal peg to "cold" and leave it there all summer (until I get a new cog that is).
When the cog broke, it must have been tuned to "kinda, sorta hot", because that is what I was getting out of the vents all the time.
I am certainly happy it's not a temp sensor thing and I don't have to tie the heater valve shut - just a broken piece of plastic.
Also good to know the fan **** doesn't illuminate - when I had the module out, I pulled the two fiber optic cables out of the white square housing that surrounds the fan **** and cut a wee bit off on the plastic shield to expose more of the optic cable and re-installed them - this made the lights brighter all around the fan ****.
One thing I did was pull out that lil' scroll piece that holds the "1,2,3,4" fan speed and cleaned up the clear plastic cover that goes over the number scroll thingy....it was VERY "hazy" - you could barely see the numbers.
Now it is so bright, I can't stop staring at it and now I can see light creeping out at the top and bottom of where the number is.
...oh, and I tried the JB Weld and even tried JB welding two washers on either side of the cog to give it more strength and it worked ok until you slide the temp slider to about the 30% mark - it seems at that point, there is some additional stress put on the cog which makes it slow down a bit and it was at this point every time that it would re-break. I tried adjusting the bigger arm (the copper-colored screw that sits in the middle of the black plastic), but this did not help.
11-02-2011, 05:44 PM
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Thanks for pointing out where the hot/cold switches are.
I'll have to re-check mine because even if that cog was broken, I should have been able to slide the slider to the extreme left and hit that sensor giving me cold air, but I was always getting a luke-warm air through the vents - even if the temp slider was all the way to the left (which would indicate the unit was pumping out some heat because it was using the potentiometer settings and not hitting the cold sensor) - perhaps the broken cog was causing the arm to not hit the switch. I'll have to pull the cover off and watch it in action to see if it hits that sensor.
Ahhhh - wait a sec, it is coming to me now in re-looking at the pic of the unit......
Without the plastic cog in the mix, the black toothed thing that attaches to the temp slider is not "locked in" like it would be if it was toothed-into the smaller cog. If I slide it to the far left, perhaps it was bouncing back slightly causing it to not rest on the switch.
Also, I now think that adjuster screw is for moving the temp slider arm slightly left or right, in case it isn't hitting the sensors correctly.
I'll have to re-check mine because even if that cog was broken, I should have been able to slide the slider to the extreme left and hit that sensor giving me cold air, but I was always getting a luke-warm air through the vents - even if the temp slider was all the way to the left (which would indicate the unit was pumping out some heat because it was using the potentiometer settings and not hitting the cold sensor) - perhaps the broken cog was causing the arm to not hit the switch. I'll have to pull the cover off and watch it in action to see if it hits that sensor.
Ahhhh - wait a sec, it is coming to me now in re-looking at the pic of the unit......
Without the plastic cog in the mix, the black toothed thing that attaches to the temp slider is not "locked in" like it would be if it was toothed-into the smaller cog. If I slide it to the far left, perhaps it was bouncing back slightly causing it to not rest on the switch.
Also, I now think that adjuster screw is for moving the temp slider arm slightly left or right, in case it isn't hitting the sensors correctly.
11-02-2011, 05:44 PM
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11-02-2011, 07:07 PM
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The **** lighting turned out pretty well, but if I were doing it on another unit, I'd probably go with an SMD LED rather than the added fiber optic filament. The fiber optic solution worked, but is way too much work and hacks up the unit pretty badly.
The fan speed dial catches its backlighting from the main backlighting bulb; the LO/FAN/HI labels get their backlighting from a couple of fiber optic filaments. Actually, I think the FAN label might catch some of the backlighting from the main backlighting bulb, too.
