Re a couple posts up, this really has nothing to with the a/c, at least not directly.

OK anyway I have some new insights. I think we may be looking at one intermittent failure and possibly a second full-time failure.

Was messing around with the car some more yesterday in some rather cold temps, not much above 0 F, not much different than in the second round of testing described earlier.

This time around, in the tests with car not moving, most of the time I just let the car idle rather than trying to hold a given RPM. Which is probably a better strategy, because small accidental variation in RPM with the accelerator pedal can give big variations in vent temp output even if the engine temp gauge stays steady. Due presumably to different rate of recirculation of coolant through heater core.

In yesterday's tests with car not moving, most of the time, turning "recirc" on or off had no discernable effect on temp of air coming out of vent. Or on the sound of the fan.

Ditto in tests cruising at 60 mph on highway, flat ground. Here the engine temp was slowly dropping throughout the test (again, think this is another problem I need to deal with) but I was still able to convince myself that the "recirc" on or off made no discernable change in vent temp. Even though it was about 0F outside and the inside had warmed up to about 50F.

But, late in the evening, when I wasn't interested in doing any more highway tests, in some of the tests with car not moving, pushing the "recirc" button on made the fan get noticeably quieter, and the flow out of the vents became noticeably less, and the temp of the air coming out of the vents dropped some. The change in sound happened about 1 second after I pushed the button in. In hindsight, I've noticed this effect many times in the past, it just slipped my mind till I was reminded of it yesterday. But it didn't happen in any of the other recent tests with the car not moving that I've posted about. Whether or not it happened in the original highway tests that were the subject of the original post, who knows-- my car is too loud at highway speed to easily hear that difference in fan speed-- but my guess now is that it did.

So a few more hypotheses -- "hypothesis 3" -- the difference in fan speed is an intentional design feature caused by sending less voltage to the fan when the car is in "recirc" mode, for any given fan setting. (All yesterday's tests were with max fan speed and max temp selected.) For some unknown reason this feature was only activating during a few of my tests-- the original ones on the highway, and the last ones while stationary. "Hypothesis 3A" -- also my flapper door is not operating properly and the car is actually permanently stuck drawing outside air, or permanently stuck drawing inside air, seemingly more likely the former because I don't have big problem with the windows fogging up. Helping to explain how the change in fan speed can be sufficient to dominate over the effect of drawing in cold outside air rather than using warm inside air. "Hypothesis 3B"-- the flapper door is operating correctly, at least during those instances that I hear the fan speed drop; I really am recirculating inside air in those cases, but the decrease in fan speed is sufficient to cause the vent air temp to drop anyway. When I don't hear the fan speed drop when I push the "recirc" button, I'm probably not switching to inside air either, hence no rise in vent air temp. I.e. two things running off one circuit that has having an intermittent failure.

"Hypothesis four" -- the difference in fan speed is entirely caused by the inside air source to the fan being more restricted than the outside air source to the fan. The car may have always been this way since new, or it may reflect some blockage to the inside air source to the fan that has developed since the car was manufactured. As long as it's not too cold outside, this drop in fan speed could be sufficient to cause the vent temp to decrease when the car is switched into "recirc" mode. The temp drop when switching into recirc mode would be expected to be greater on warmer days than on colder, which seems to be consistent with the difference between what I saw on my very first test that was the subject of the OP, and the very last test described here. (Unfortunately though those tests aren't that great to compare because the first one was during highway driving and the last one was with the car idling stationary.) A key part of this hypothesis is that in all other tests besides those two sets, the flapper door was not actually moving to change between outside air and inside air when I pushed the "recirculate" button in, for reasons unknown to me, even though the light on the button was going on. Hence no change in fan sound, no change in vent temp. So there's an intermittent failure of the movement of the recirculate flapper door going on. This hypothesis seems the simplest because it only involves one intermittent failure rather than an intermittent failure plus possibly a second full-time failure. It's hard to convince myself though that it could be sufficient to make the heater vent temp be higher when drawing in 0-degree outside air than when recirculating 50-degree inside air, during those very first and very last tests where the flapper door presumably actually was operating properly . But, maybe....

Note that hypothesis "3B" and hypothesis "4" are essentially the same in terms of at which points in which tests I believe the car was drawing in outside air or inside air. The idea is that in all tests when the car was actually recirculating inside air, the fan speed was also reduced, but in many of the tests for reasons unknown to me neither of things were happening when I pushed the "recirc" button even though the light went on.

I no longer believe that some of the air being moved by the fan is bypassed around the heater core in "recirc" mode but not in "non-recirc" mode. That just doesn't make sense, as to why the car would be designed that way, or how the ducting would be physically constructed to get that effect, or what kind of failure could happen to cause that effect. Nor do I believe that there is much "ram air" effect augmenting the fan during highway driving when outside air is selected. That doesn't mesh with the results I obtained in yesterday evening's highway tests, described early in the present post, and also with the fact that so little air comes out of the vents when the fan is off during highway driving when outside air is selected. Maybe if you open the back windows a bit to get strong suction effect or something, but I wasn't doing that.

Sorry for so many words! Will update when I learn more--

 

I was cutting down the car, not you. Sorry if you felt offended. I had a 1990 Buick LeSabre for a while, what a wonderful trouble free far. Comfortable, quiet, great AC and sound system, plenty of pep,

But I like my 92 SL, I put in a full on roll cage, moved the battery to the trunk, ripped out the AC as mentioned, you can actually work on it now.
Also put in a custom oak wood console, converted the auto seat belts to regular, sealed up the sun roof with urethane, ripped out the sunroof motor and cables,

I also installed miniature LED volt meters for
MAP Sensor output,
Throttle Position Sensor,
Air Intake Temperature,
EGR Relay voltage
I am in the process of installing a liquid filled vacuum gauge for manifold vacuum,
And also an analog volt meter to track the O2 sensor. The LED display does not track the O2 sensor very well.

The roll cage really stiffened the frame up. It corners like a Lamborghini now. The other day some jackwagon decided to make a U Turn in front of me from the emergency parking lane. Swerved that car as hard as I could and zippped right around him, felt like I was pulling about 5 G's.

 

I'm not offended in the least.
It's the passing of judgment on those others with no knowledge of their motivations that pissed me off. Our microcosm will be fine if everyone meets the minimal standard of mutual respect.

Some unique mods there

 

New observations-- with a couple of specific questions at the end (please see items 6 and 7)

1) There is definitely an intermittent nature to operation of the "recirculate" door on my car. Sometimes I hear the sound of the airflow / fan noise change when I push the button, sometimes I don't.

2) About the theory (post #11, "hypothesis 3") that a different amount of voltage may be (possibly intentionally) going to the blower fan when the car is in "recirculate" mode-- I've discarded this idea. I did measure the voltage across the blower motor during a time when the "recirculate" system was activating properly and I could hear the airflow / fan noise change when I pushed the button. At best my meter was indicating a 0.06 V change (drop) in voltage across the fan in "recirculate" mode and that's not going to change anything (and may just been a measurement error). You have to make this measurement by sticking pins in the wires when the fan is actually in operation. With the car idling, voltage across the fan was about 12.90 V highest "fan" setting, with the lower settings being 10.25 V, 8.51 V, and 5.80 V. If you try to just unplug the fan and make the measurements at the connector, you only get about a 0.04 to 0.06 V difference between the highest fan setting and the lowest fan setting. I guess that's the nature of electronic controls.

3) Here's a link to a youtube video showing how to check the operation of the temperature lever and vent / bi-level /floor / defrost lever on a Saturn Series: . This mixing control box is nowhere near the location of the "recirculate" door. There's no way that operating the "recirculate" door could affect anything in this mixing control box.

4) Here's a link to a youtube video showing the operation of the "recirculate" door. We're looking at the top of the dash area, passenger side -- nowhere near the mixing box shown in the previous video. The video is set to open at 1:11 which is when you get to see the door move: . That's what's intermittently not working on my car. During the times when it is working, if the fan is running I can hear a change in the airflow sound-- it gets a little quieter, and the fan speed seems to decrease slightly, after I push the "recirculate" button. Also I noticed that, during the times when the "recirculate" function does seem to be working, then when the blower motor is physically unplugged so that the fan doesn't run, and the car is switched "on" but not actually running, things are quite enough that I can actually hear the "recirculate" door moving, or its actuator motor operating, after I push the "recirculate" button. Fan speed selector must not be in the "off" position, otherwise the recirculate button doesn't do anything and the light on the button doesn't come on even when the button is pressed in. During the times when the "recirculate" system is failing, as I've determined is happening intermittently, then I no longer can hear the "recirculate" door moving when I push the "recirc" button in the test described above (i.e. the fan speed selector in an appropriate position, fan unplugged to eliminate the fan noise, key "on" but engine not running), even though the "recirc" button still lights up when I push it in.

The whitish round thing in the video appears to be the squirrel-cage blower fan itself, though the blades are hard to make out. You can see why opening and closing a door that close to the blower fan might affect the fan noise.


5) Back to the original question that started this thread-- why, when I measure with a vent air temperature sensor, was I consistently finding that the air temp coming out of the vent was consistently at least 20 F *lower* when the system was in "recirculate" mode? Cruising at a steady speed, steady engine temp at 60 mph on the highway on a 30-degree F day with max fan speed, max temp selected? Keeping in mind that there's no form of automatic temperature control on this car (at least when you are not using the a/c which is a different can of worms completely)? I think it's simply because there's a smoother and/or larger-volume air intake path when NOT in "recirculate" mode, and thus a higher volume of airflow being moved over the heater core. Seeing this happen to some extent while the car is idling also suggests it's not primarily a "ram air" effect caused by the car being in motion. It's possible that (at least during the times that my "recirculate" button is working to open and close the door as shown in the video in item 4) the car is operating exactly as designed, despite the fact that it is heating the car better when not in "recirculate" mode. (At some low enough outside temperature, this will surely no longer be the case, but my tests in post #11 suggest that this "break even" temperature is somewhat lower than 0 degrees F, at least in the case where the car is sitting there idling.)

6) I still have some questions about exactly what we are seeing in the video in item 4 and would really appreciate some input from anyone who can shed some light on this. The video implies, but doesn't ever clearly state, that closing the door (i.e. when it comes into view at 1:11) is what happens when you depress the "recirculate" button so that it lights up. So the big rectangular opening that we see before the door closes, is connected by ducting to the outside vents right under the windshield? Is that correct? Or am I getting it exactly backward, that that big rectangular opening is where the air gets drawn in while operating in "recirculate" mode?

7) Also, when the door slides out of view, is it sealing anything off, i.e. the source where the air gets drawn in while operating in "recirculate" mode? Or is it simply sliding out of view and doing nothing, which would indicate that there are source(s) for inside air to enter the system that are simply open all the time, regardless of whether the "recirculate" door is open or closed? The latter situation would mesh well my idea that the total intake path is larger in volume when the car is not in "recirculate" mode, and with my observation that the system sounds quieter, not louder, when the system is in "recirculate" mode. That would make sense if you were closing the outside air source but weren't opening any new inside air sources.

Any knowledgeable input on points #6 and #7 that is appropriately specific to the Saturn S-Series, would be much appreciated. Thanks! I haven't been able to find any other relevant videos or detailed text descriptions on line yet.

I would also be interested from anyone else willing to take a drive in cold weather in a S-Series with a temp probe in the vent and confirm that you are seeing the same effect that I am, i.e. going to "recirculate" actually makes the vent air temp decrease. Best conditions for tests are-- cruising w/ cruise control on flat ground with engine warmed up to a steady operating temp, or sitting idling at a steady RPM with engine temp holding steady. I'm now about 98% convinced that what I am seeing is normal and other testers will get the same results, at least for outside temps not below 0 F and inside temps not above sweltering.

A few final notes: re the second video, if you click on "You Tube" to watch it in "You Tube", you'll see a comment suggesting that if you want to just unplug the actuator and leave the "recirculate" door in one position, the "door closed" position would make the most sense for most effective heating / cooling. If my understanding of how everything is working as suggested in #5 and #6 and #7 is correct, that appears to be the wrong conclusion, at least in regards to heating the car, at least with outside air temps 0F or higher. Cooling opens up another can of worms. Since the a/c system has temperature-regulating functions that slow things down if getting too cold to prevent icing up, it would seem that blowing as much air through the evaporator as possible would be even more beneficial than blowing as much air as possible through the heater core, which would seem to favor *not* using "recirculate" for cooling. But the glove box manual states that cooling is more effective in "recirculate" mode. So it seems I am still missing something. Btw it also states that air from the heater outlet down near the feet is slightly hotter than air coming out of the vents. I wonder why the system would be designed that way. I used the vents for all my tests simply because it was easy to stick a vent temp thermometer into the vent.

 

Re previous post:

I found a drawing of the whole system: https://saturnarchive.com/service-ma...spsdsubkey=582

The implication seems to be that interior air is not supposed to be drawn into the system at all when the system is not in "recirculate" mode, but I can't really tell that for certain.

Questions in previous post, see items #6 and #7, remain unanswered.

The moving door seen in second video in previous post above appears to be physically located high in the upper left area of each diagram. A/c condenser on left, heater core on lower right.

Document says a/c is most effective in "recirculate" mode, but doesn't comment as to whether or not same is true for heater.

Relevant: "When defroster/defog is selected, the controller will return the HVAC module operation to the mode that draws fresh outside air into the vehicle regardless of the position of the Recirc button."

(None of my tests were in "defrost" mode, but the lever was occasionally moved into "defrost" which could have conceivably played some role in the intermittent nature of the failure I'm seeing?)

Right now, the LED on "recirc" button is lit whenever "recirc" button is depressed (and fan is on), even when I move the mode selector to "defrost". That may or may not be normal. Maybe the note on the diagram is correct but the LED simply isn't designed to turn off in such a case. At present, my car is back in the failure mode where recirc door isn't actually moving when I push the "recirc" button even though the "recirc" LED lights up. Next time I detect (via the change in airflow / fan noise) that the "recirc" door is moving again, I'll take a closer look at happens in "defrost".

I also found this circuit diagram https://saturnarchive.com/service-ma...bid=536&evc=sm which appears to me to suggest that selecting defrost mode should actually not stop the "recirculate" door from operating normally in accordance with whether or not the "recirculate" button is depressed. So maybe the note on the other set of drawings was wrong.

But the "defrost" issue is really just a distraction. What I really want to know is, A) in the second video in previous post, is it correct that the door "closed" (visible) corresponds to the "recirc" function active (i.e. button depressed, LED on), or is it the reverse? And B) is the door acting to open and close both the outside air source and the inside air source in alternation, or does it only open and close the outside air source while the inside air source stays always open, or does it only open and close the inside air source while the outside air source stays always open?

 

Really I'm more confused than ever. I think I had it all backwards. The large rectangular opening prominently visible around 1:11 in the second video 2 posts up is probably where the interior air enters the system when "recirculate" function is engaged. Neither the video, nor the drawings linked in post #15 are making it clear to me whether the outside air intakes are supposed to be fully sealed off, or maybe just partly obstructed, in "recirculate" mode. Nothing explains why fan noise gets quieter as heard inside the car in "recirculate" mode, or why vent temps are lower. Especially during instances where car is idling so "ram air" pressure cannot be a factor. Is there any chance at all that my "recirculate" actuator, during those instances that it actually does actuate (considering that there is evidence of intermittent failure to actuate), is doing the exact opposite of what it's supposed to do when the "recirculate" button is pressed? Moving the door in the wrong direction? Baffled and back to square one...

 

Well folks I now suspect that the above is indeed exactly the case.

Somehow.

Maybe the actuator "slipped a cog" or something?

Here's the test that convinced me.

Temp lever full cold (but apparently temp mixing door or flapper doesn't quite close all the way or move as far as it should, so some air is still moving through the heater core and then out through the vents.) Mode lever in "vent" position (full left.) Fan on full. Engine temp stable at middle mark (1/2). Outside air temp about 65 F. Car idling not driving. No possibility of "ram air" effect through outside vents. Windows closed. "Recirculate" button not pushed in to engage, green LED there not lit. Vent temps slowly rose over several minutes from 108 F to 122 F and then seemed to stabilize. During same interval car inside indicated temp slowly rose from 91 F to 93 F and was probably still rising. (There is probably a significant lag in the thermometer laying on the passenger seat (in the shade) that I used to measure car inside temp.)

Then I pushed the "recirculate" button in and got the green LED and heard the fan sound get more muffled as heard from inside the car. (I think that's a better description than saying it sounds like it "slows down"; also I really can't say I sense any decrease in speed of airflow out of vents when this happens.) Over just a few minutes, vent temp dropped to 100 F, even as temp on thermometer laying on seat inside car (which probably has a lot more lag than vent temp thermometer) showed temp inside car rising to 94F. Engine temp still stable on the heat gauge, and no change in the RPM at which the engine was idling.

Then I moved the temp lever to full hot and the vent air temp rose to neighborhood of 176 to 180 F. I turned the "recirculate" button on and off several times. Temp on thermometer on seat continued to slowly rise, reaching 103 F by the end of the test. Changes in vent temp associated with changing the "recirculate" button seemed now to be only a few degrees but the direction of the changes remained consistent with what was described in previous paragraph, and opposite to what would seem to be "expected" or "normal". I might have seen bigger changes if I had let the test go on for more minutes between each change, more like in the earlier test, but things were getting pretty hot in the car.

The next test was going to involve a more moderate setting of the heat lever. I moved it full to the left and then back right about 2/3 of the way toward the middle. Also I opened all the windows. I was seeing vent temps around 144 F, and a temp on the thermometer lying on the seat around 105 F, when I realized that this part of the test was pointless because the recirculate door had stopped moving again - I was no longer hearing the sound of the fan get more "muffled" every time I depressed the "recirculate" button and got the green LED. If it starts working again, I'll try it again.

So that's the only thing that makes sense with all the tests to date -- during the times the "recirculate" button is doing something rather than nothing, it is very consistently moving the "recirculation" door the "wrong' way.

Saturn S-series owners, there's one simple test you could do to help me out. You don't need to mess around with a vent temp thermometer, and you don't even need to start the car. With key in "on" position and fan running full (or any other position other than off), and mode lever full left (or really in any position other than defrost), would you say as heard from inside the car, the sound of the fan becomes more "muffled", or less "muffled", when you push the "recirculate" button in and get the green LED? My experience is more "muffled", but I now believe it should be the opposite, as the "recirculate" intake door, located right above the fan, should move forward (toward the front bumper) to create a direct opening to the inside of the car, up under the dash. I believe my "recirculation" door is opening (moving forward/ toward the front bumper) to let inside air into the system when it should be closing to exclude inside air from entering the system, and vice versa. (I still don't know for sure whether outside air is meant to be entirely excluded, or only partially excluded, or not particularly excluded at all, from the system when the "recirculation" door is in the forward position, toward the front bumper, but it really wouldn't seem to matter all that much in regards to diagnosing the present problem.)

But, still another piece of the puzzle that has not yet fallen into place for me, is why in the comments for the second video two posts above, someone thought that "you would get a stronger fan for your heat and AC" with the "recirculate" door permanently fixed in the closed position. If opening the door creates a direct (intake) connection to the inside of the car, right there immediately above the fan, then ... how does that idea make any sense?

PS -- about the "defrost" setting of the mode lever- during the part of the test where the changes in airflow / fan sound told me that the "recirculate" button was indeed having an effect, I briefly moved the mode lever full to the right to the "defrost" position. Pushing the "recirculate" button in and out continued to turn the LED on and off and continued to make the fan / airflow sound grow more or less muffled. So I think at least in relation to my 1997 SL1, the technical sheet with the drawings, linked 2 posts up, was wrong when it said the "recirculate" function was disabled whenever the mode lever was full to right in defrost position. Unless that's something else that has somehow failed on this particular car, which seems(?) unlikely.

My next step will probably be to change the "recirculate" door actuator, because I don't want to get stuck with the door failed in the position where I am recirculating inside air, due to concerns about windows fogging up. I have an impression that during the intermittent failures of the "recirculate" door to move, it is very strongly biased toward failing in the position where fresh air is coming in, but I couldn't really say what I am basing that idea on, except that I don't have a lot of problems with windows fogging up. Maybe there's no truth to it.

 

I did the test and the air flow sounds noticeably louder when recirc is turned on. So less muffled. This is on my 97 SW2.

 

Know it from memory on my 95 SC2.

 

Thanks for both of the above posts. Confirms what I expected as per post #17. And my car is doing the opposite.

That sure threw me for a loop. I wonder if replacing the actuator will put things right, or if it's in the control system --