Re: And another problem...

There is something going on with the heater (auto climate type) that when the auto feature is disabled and I have the thing in "Manuel" mode with the temp control set to "Low" and the cabin fan speed adjusted to something not too drafty the air from the vents is a bit warm. Not fry eggs warm but warmer by a noticeable amount.

The other night with the window down the air from the vent was warmer than outside air. I can try a digital temp thermometer but really I feel comfortable/confident with my diagnosis based on how the air feels to my hand.

Now, the car's cabin has been running warm for a while even with the A/C on. That is the cabin temp (72F) is ok but I noticed the cabin vent fan speed once the cabin temperature is stabilized ends up a few lines faster than I remembered it being.

I actually brought this up to the SM thinking the A/C was in need of recharging (or something else) and he had a chance to drive the car the other day and reported the A/C blew cold air real quick when turned on just like the new cars he drives.

But I think what's been going on is there is some problem with the air flaps inside the unit and some air is being routed through the heater core even though based on the control temperature setting no air should be routed through the heater core.

After I get my 996 back from the service department (it is in getting a new T-stat, water pump, driver side radiator fan motor/blade, and two new front diff seals) I will have the Boxster A/C system looked into.

Either leak or stick. Basically, you have a system with a cold ( and i believe fresh untreated..) air feed from the A/C and a warm air feed from the heater core. Temperature is basically set by blending the two. SO if the heater core one is drafty... it will leak hot air.

I dont know how easy or difficult it is to get at those blend doors, or if there is a known solenoid issue or ....

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

due to a bad temp sensor in the A/C head unit. He can use the diagnostic computer to check this sensor's performance.

He said he's never had any cars in for any problems with the blend doors. The symptoms have been no cold air or a noisy cabin fan.

Before I unleash the tech on the suspected blend doors I need to check the air temp from the center vents and compare it to outside air temp and see if there is any heating of the air from the vents which would point to a blend door issue. It feels warm to me but I could be imagining things. Also, I need to double check my results with my other car under the same conditions.

Very occasionally, the air was not routed properly as if it got confused and did not respond to position changes. I did not notice an issue with air temperature but air routing. I forget what I did but I put the fan on high (no real reason other than I am getting serious with it), and cycled through the positions over and over and hit Auto, then back through. Seemed to clear it up. Definitely something would get confused and my impression was that it was mechanical and not electronic.

Just a suggestion.

Peace
Bruce in Philly

There is one blower fan. It either blows cold, ambient, warm or a combination of those airs. Its volume is nto the issue -- or i need to hear more if it is.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
grant
There is one blower fan. It either blows cold, ambient, warm or a combination of those airs. Its volume is nto the issue -- or i need to hear more if it is.

Grant

There is of course just one cabin heater/AC blower fan.

(IIRC, there is a small fan behind the small round grill in the dash on the right side of the car which houses the cabin air temp sensor. This fan pulls air over/past this temp sensor so the A/C control unit knows what the cabin temp is at all times when in auto climate control mode. In this mode the controller will adjust the blower fan speed and the blend doors and even the A/C compressor displacement to maintain the temperature set on the auto climate control panel. I wonder if this fan is maybe not turning anymore? Hmmmm. I will have to check this out.)

All I'm saying in auto mode after the A/C has been on a while and the cabin vent fan speed has stabilized it does so at a couple of speeds (bars) higher than it used to. This suggest to me the auto climate control is running the fan faster to maintain the 72F I have set the auto climate temp control to than it used to.

In the past, once the cabin temp was stabilized the fan speed would drop to around the 1/3 level. Now it runs near the halfway point. (The 996 fan speed drops to around the 1/3rd level too under similar conditions. The Boxster A/C has always impressed me with its ability to bring the cabin air temp to the desired temp with no muss no fuss and once there to dial things back so one doesn't even know the thing is running other than it can be blazing hot (or freezing cold) outside and just right inside.)

Based on what I perceive as a temp difference between outside air and air coming through the center vents with the auto climate set to manual mode and the temp control set to low which should mean outside air is getting fed directly to the vents and should *not* be passing through the heater core (IIRC it passes through the A/C evaporator though) I believe the flap that routes air around or past the heater core is leaking some air through the heater core for the air out of the center vents after the car has been running a while feels warmer than the outside air.

I will dig out my digital thermometer this weekend and after the car has sat overnight and should be at ambient drive the car while measuring ambient air and cabin vent air temps to see if the vent air temp climbs as the car warms up as the coolant gets up to operating temperature.

The tech must be wrong, because for him to be right there would have to be more than one fan - one dedicated to the heat.
It must be another cause. Or something strange is going on in the design, which I'd like to know...

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

[unityhoops.com]

Marc; There can be a problem with the blending door, depending on the year of your Boxster. My MY 99 puked foam out of the vents for quite a while and then I found the source: The blending door had a foam covering and when the foam degrades, huge holes open up in the door. The holes were for making the part lighter I suppose. My symptoms were similar but I had trouble getting much heat in the winter. You could still have a blend motor problem but if you have seen foam coming out, then you might have the dreaded door problem that I had. Several fixes are around and I can forward my procedure if you think you need it.

that arises from the foam coming loose and getting into the fan.

After some more time, and with the onset of much cooler weather -- finally! -- I'm thinking the suspected problem with the door or flap that controls the heat is my imagination. The other night in cooler weather the air was cold enough that I was waiting for the appearance of the warmer air and it never showed up. I had to actually raise the temperature some to take the chill out of the incoming air and the cabin.

Anyhow, my plan though is still to confirm the air from the vent is not heated even when the temp control is set to low.

Yes an imagined problem is easier to fix than a real one! Although what you are describing is more or less how mine acted. It just didn't warm good in the cold. You can check that the door is modulating by scooting up under the dash and watching the motor and levers move. If you raise/lower the temp you should see corresponding movement of the lever. If the lever is responding to input from the controller you may want to check the blending door. It is viewable by removing the heater core which believe it or not is real easy on the Boxster. You just have to plug hoses and core quickly to avoid losing that expensive Porsche coolant. There are a lot of things this could be; just sharing how it was for me...

Blending flaps, blower fans, auto climate control.... Gone are the days ('69 Bug) where you pulled a lever for hot air from the engine compartment or opened the window vents for cool air

again on a work commute during the '71 winter and the thing had no heat output at all. I never got a chance to see how the windows worked in the hot weather cause I bought a motorcycle and commuted on that. I was warmer on that thing wearing my riding gear than I was in the VW.

Quote
SMILIN
Blending flaps, blower fans, auto climate control.... Gone are the days ('69 Bug) where you pulled a lever for hot air from the engine compartment or opened the window vents for cool air

Good luck with that "hot" air from the VW air cooled engine compartment on a cold (-10 F and down) winter day. Canadian cars got a supplemental gas heater about 1966. I know my '67 had (and needed) one.

including the pre-electric-heating rear window defroster vents. (The heat exchangers were built around the exhaust manifolds.) Like a scene from some spy movie.
Concerning no heat output, I vainly looked for an image of the "Generic Car" ad featuring Lee Iococca in the "Not The New York Times" parody: "If you're cold, wear a coat. If you're hot, take it off."



Edited 2 time(s). Last edit at 10/04/2013 11:40AM by Laz. (view changes)

ridden to school in DC throughout the 1960-1961 winter in a Model A sedan with only the engine fan blowing heat through a tube that sat on top of the manifold and let air very slowly into the cabin through a hole in the firewall. Just the one tube on the passenger's side IIRC. No defrost at all. Narrow slick tires. 6"+ of snow never stopped us.

An engine block for one of those cost $25 at any wrecking yard.

Have we made progress?

PS: Saw only my second 981 this week...black one headed towards Pinehurst.