850 GLT Wagon - 1996 - Climate Control seems too cold

[s2zeller]

After getting very cold air blown on me (and what seemed to be approximately correct temperature air scrimpingly doled out to the passenger side) once again, I finally popped off the plastic vents for the cabin temp sensors and used alcohol and several q-tips to clean out a lot of lint.

The motors on the sensors spin right up when turning the ignition on, so it looks like no seizure.

This morning, the driver-side and passenger-side output seemed pretty similar (passenger-side temperature maybe slightly warmer and slightly less in output volume)... but the real test will be on the drive home after the car has been sitting in a sunny parking lot all day.

[s2zeller]

Well, I'm a bit perplexed...

For the first 70 miles it acted much the same as before, tho' not quite so much

Initially, both were putting out some cold air in roughly the same volume, but then the passenger-side vents tapered off while the driver-side vents continued to push colder air (tho' not quite so much nor quite so cold it seemed).

I stopped to run an errand, then started the car up again... and it started getting warmer in the car.

No flashing AC/REC lights have been seen for at least 6 weeks (I think longer), so would an error code still be stored somewhere?

All vents seemed to be pushing out the same temp air in roughly the same volume (the passenger-side vent might be a little lower in volume).

I stopped again... this time parking it for about 2 hours. When I got in, all vents again started pushing the same temp air in roughly the same volume.

So, does the ECC need to relearn from the sensors, or is my driver-side sensor (or ECC control unit) flaky?

[nightc1]

For the length of time for the car to warm up this sounds like a Thermostat left wide open in the engine. I had this happen on my 94' 940 and it wasn't an issue in the summer but when the winter hit it made getting the car up to temperature difficult and getting warm air from the vents just as big an issue.

When you run it manually does it heat up and cool down as it should? This is when on AC and set cold on both sides it pumps out cold air like there is no tomorrow and when the ac is off and temperature turned fully up that it pumps out nice hot air without issue? If both work fine manually then, my opinion is it's something in the sensors or climate control itself but if it takes a long time to heat up then it's the engine thermostat. I've not changed mine on my V70... but on the old 940 it's was a fairly easy job and pretty cheap to do myself.

If it's the sensors then you can do some more cleaning. I wonder though are the sensors interchangeable right to left? If so you could swap them and see if the problem flips sides of the car. If it doesn't then that would point to the climate control unit itself. It could be a faulty connection from one side... or a fault in the unit. If it's a fault in the unit, I would just learn to run it manually. That is, if you just want outside air then turn off the air, set the fan speed to what you like, and the temperature to whatever you want (or all the way cold if you just want outside air without the heat). In that setup you don't need to fiddle with the unit at all except when you want the ac to run which you can press without looking at the unit with a little practice.


EDIT:

Did some research,

There are 2 other sensors in the ducts for passenger and driver side. If you download the Volvo_850.zip file that's on this site (i'm sure someone will link it or you can google it and it should show up) and look at the "ac heater system auto.pdf" file it should show you the general area of where to look. I have a 99' V70 and it has helped greatly in searching for stuff. Also of note the solar sensor on the dash, the coolant temperature sensor in the engine and the ambient air sensor in the cabin air filter compartment play in greatly in how the auto control system works.

Something else I read, and this applies to my car and maybe not yours, but there is a temperature sensor to the left of the temperature control unit on the dash itself. I have it in my V70 and I think my 94' 940 had it as well... this picture shows it but it's not the red arrows but to the left of the control unit on the dash itself and looks like a tiny circular vent:


I read that it plays into the temperature control, but it's not in the documentation so I don't know if that is true or not. Maybe this is part of the drivers side duct temperature sensor? Either way, it's easy to get to and easy to clean out (if you have this).

Also, of note, if you download that documentation it tells you a way to test the sensors with an ohm meter. So you can do it without needing the full diagnostics on the unit (though reading the codes would be much better if you can get a dealer to diagnose the issue for cheap/free).

[s2zeller]

Well, this morning, things behaved much better. By and large, the temperature and air flow were very much the same for the whole 1.5-hour commute. If pressed, I'd say that the center console driver-side vent was a bit cooler than all of the others and had a slightly higher output than the passenger-side vent in the center console. So, I'll be continuing to monitor this.

Having had a thermost fail during a sub-zero (Fahrenheit, that is) stretch a few winters back, I'm thinking that this isn't that (also - not that it would necessarily negate the possibility - I just had a new thermostat put in about two months ago... which was after I began thinking something was a bit of with the cabin temperature).

However, I will keep that in mind.

At first I was thinking that the passenger side was failing to cool properly, but now I'm thinking that the driver side is cooling when it shouldn't be.

The air flow volume issue may or may not be related (right now it seems to be linked... but I'm still not sure).

I haven't explicitly tried manual... just changing the temp while on AUT. I need to do that and will endeavor to do by next week if the problem truly hasn't disappeared.

Kind of funny how spoiled one gets... the car I drove up until last year was a '91 Jetta with a broken AC (and even when it worked, I had to manually fiddle with it to stay comfortable).

Thanks for suggesting swapping sensors... that sounds like a great diagnostic if it comes to that. I really need to remind myself to try the simple stuff first and not move on to something more complicated when not warranted.

I also appreciate pointing me to that .zip file. I'll give that a look... especially if there are other sensors that could be as lint-covered as the two I cleaned (and - yes - I should revisit those with better light to make sure I got everything).

[s2zeller]

Again, the AC started out better than it had, but as the drive wore on the driver side got cooler and higher volume (tho' not quite so much as before).

And also again, when I stopped and restarted the car the driver side started behaving properly.... which almost seems like a reset of some sort.

[s2zeller]

Well, I can safely certify that the cabin sensors are NOT interchangeable between passenger and driver side...

While I had them out, I did disassemble them a bit more and clean out as much lint/dust as possible before re-installing them.

Now, I am thinking that I may have misinterpretted the "reset" after restart that led to what seemed like better behavior.

I clearly demonstrated to myself today that the output gets greater and colder if the driver-side temp dial is set to 79. The lower I go, the more normal it behaves (so - contrarily - it gets less cold and less volume as I dial it to lower temperatures... at least down to 72 or so).

What I find very interesting is that as soon as I turn it to 80, hot (and I mean very hot) air starts coming out.... accompanied by a lot of blower noise from all over (tho' - oddly - I don't feel this desert gale other than the rising cabin temperature).

I'm assuming that the passenger side - which gradually changes over from cooler to warmer - is behaving more appropriately.

I did pull the ECC control unit from the dash and everything looked properly clipped together. I couldn't get the duct sensors out, but it looked generally less dusty in there.

I'm off to reinstall the sensors and we'll see what tomorrow's drive brings.

[s2zeller]

As expected, no change in behavior.

I did finally try tuning the AC switch to Off from Auto (while leaving the center dial and fan slider at Auto).

Of course, I'd pick a nice misty morning to do so and the rise in humidity inside the cabin was immediately noticeable.

It took a few minutes, but the output of the passenger side and driver side eventually seemed to become more uniform in both temp and output.

Flicking the AC back to Auto returned the driver side to being colder and a bit higher volume.

Would the next step be to get the control unit read for error codes (despite the fact that there are no blinking lights at start-up)?

Or should I try a little harder to check the in-duct temperature sensors? Along those lines, how does one pop out the vent louvres from the center console (as I'd like to get a better look down the ducts)?

[s2zeller]

So I'm thrashing around for more data and find that AUTO has nothing to do with the cold coming out of the driver-side vents.... it is just whether the AC is on or not.

With the slider off AUTO and the center dial off AUTO, and the AC on I get cold air until 79 degrees and then hot air on 80 (or maybe it is 80 and 81, respectively).

Looks like I'll either have to settle for more manual adjustment or take it in to see if there are any codes.

[s2zeller]

I have been driving with the AC off and the dials on other than Auto, and I still notice that the center console driver-side vent is colder than all of the others.

Then, I read the Owner's Manual and it shed a bit of light on my problem (from p. 1:19):

The center panel vents have an air mix function which allows fresh air to enter the passenger compartment when the vents are open. This function is designed to allow you to direct cool air toward you face while directing warm air to the rest of the passenger compartment.

Sure enough, the Airmix is on full.

So, that explains why I have cold air with AC off, but should it also be colder with AC on?

And why the sudden change over at 80 degrees (give or take a degree) regardless of outside temperature?

And does that mean *both* center console vents are subject to the Airmix control, or just the driver's side vent?

[Romort628]

I have been driving with the AC off and the dials on other than Auto, and I still notice that the center console driver-side vent is colder than all of the others.

Then, I read the Owner's Manual and it shed a bit of light on my problem (from p. 1:19):

The center panel vents have an air mix function which allows fresh air to enter the passenger compartment when the vents are open. This function is designed to allow you to direct cool air toward you face while directing warm air to the rest of the passenger compartment.

Sure enough, the Airmix is on full.

So, that explains why I have cold air with AC off, but should it also be colder with AC on?

And why the sudden change over at 80 degrees (give or take a degree) regardless of outside temperature?

And does that mean *both* center console vents are subject to the Airmix control, or just the driver's side vent?

both center ones are bringing in the cool air.