jim010

I'm open to ideas.

After the thermostat change the car did get to 80 Celsius , but took a while.

DBJoe996

When, if ever, has the water pump been changed? The plastic composite impeller does wear and maybe it is not pumping enough coolant. Just a thought....although I would think that that would make the engine run hotter, not cooler. Hmmm...maybe enough coolant circulation for the engine but not enough to reach the heater core. Just guessing at stuff right now. Did you block off the outside air intake like I suggested? Just place a plastic bag over the pollen filter.

One other question, are your radiator fans running? Do they work? Is the ambient outside air temperature sensor correctly fitted in the front bumper?

Another question, what type of thermostat did you install? The only thing that controls engine temperature is the thermostat. If the engine is not getting hot enough, something is wrong with the thermostat (or the radiator fans are running all the time). Do all the controls on the HVAC work? Are you running the HVAC on auto, or leaving that off and going up to the highest temperature on the display?

Porschetech3

I agree with DBJoe, you need to figure out if the HVAC is not extracting the heat from the heater core, or if the heat is never getting to the heater core.

Scientifically speaking, heat (energy) can not be created or destroyed, only moved or changed in form.Also there is no such thing as "cold", it is the "absence of heat"

Since your in Canada and the ambient air has most of it's heat removed, I would perform tests in a closed garage ( with exhaust routed outside) to minimize the effect of ambient air and especially wind, and in having the car stationary will maximize heat concentration.

Since the heat (engergy ) of the gasoline is released or moved during combustion, some is used for energy to turn the crankshaft, and some is transferred to the oil/coolant. Use a Laser thermometer to check temperature of the coolant hoses and heater core hoses, the temperature of the engine outlet coolant and the inlet of the heater core should be very close to the same. You must find where the heat is going, or not going.

You can use this HVAC hack to get some temps from varing sensors to help in diagnosis.


To access diagnostics:

Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit.
Here is a list of what can be seen:

0c - ERL
1c - Oil Temp?
2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash.
3c - Outside temp. Sensor located inside the air inlet of the A/C unit.
4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the Climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temperature sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp.
5c - Outside temp. (matches with OBC outside temp display)
6c - Coolant temp.
7c - Footwell discharge temp.
8c - Sun sensor (dash top)
9c - Sun sensor.
10c - Passenger compartment fan speed.
11c - Passenger compartment fan voltage.
12c - Temperature mix Flap command 1=COLD, 100=HOT
13c - Temperature mix Flap position
14c - Central Flap command
15c - Central Flap position
16c - Footwell/Defrost Flap command
17c - Footwell/Defrost Flap position
18c - Recirculation Valve command 1=OFF, 100=RECIRC
19c - Recirculation Valve position (feedback)
20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer)
21c - Engine RPM in hundreds. This too only updates once per second.
22c - ?
23c - ?
24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum.
25c - ?
26c - ?
27c - ?
28c - Fan speed?
29c - ?
30c - Engine run time in seconds (255 max.)(=0xff)
31c - Timing counter
32c - Displays test
33c - Software version? Mine states 3.4
34c - ?
35c - Outside temp. from inlet sensor (filtered?)
36c - temp?



.

jim010

I'll take time later to read your post in more detail, but to answer a few things:

HVAC functions were all tested.

tested heat on manual high and recirculate. Recirculae is the warmest.

Thermostat installed by Porsche.

temp got to 80 gayer driving a while

hoses to heater core are very warm but not hot. I can hold them

water pump impeller blades in good shape.

DBJoe996

Huh. I would borrow or buy an infrared thermometer and measure the temperature at the thermostat housing and then the heater hoses. They should be about the same temp.

jim010

My father in law has one. I will check Friday

RngTrtl

I dont have any ideas, but there is something for sure wrong. The heat on these cars, even in sub freezing conditions, should be enough to run you out of the car in 10-15 minutes.

911Syncro

My car has similar symptoms. On a cold morning, I have the temp set to maybe 74 or 76, figuring the controller will know it's cold in the cabin and then crank up the heat, but then after 10 minutes it still doesn't blow nice hot air, only warm air. But if the temp is set to max, 85 or something, then suddenly in a few seconds very hot air starts coming out of the vents. Has anyone noticed something similar? I don't think it is related to the thermostat, but maybe the temp sensor is degrading?

bbboomer67

I think your problem is that the foam on the Heater/AC diverter (flap) has deteriorated which causes a loss of heat. There seem to be lots of threads about repairing the foam on the flapper. Evidently this problem affects all 996s!

jim010

Im sold on the idea of the foam too. Just the hoses to the heater core only being quite warm rather than hot makes me wonder.

Balu

You mentioned Porsche did the thermostat.
Did they vacuum purge and fill the system?
If not perhaps it's trapped air?

I've got a Schwaben vacuum system here from
last years rad/fan replacement that I'll send to you
if need be.
I don't expect shipping from Revelstoke to be too much.

Also don't expect it'll be difficult for you seeing some of the
work you've done so far and with DBJoe and Porschetech3
on board surely you'll get to bottom of this.

jim010

They assured me they they gat trapped air out. I made sure to ask after you guys pointed it out after I did the heater core..

And I am very appreciative of the help. The Porsche tech says he goes on here too for troubleshooting, so he may well have read this thread.

TomR9964S

I agree with your statement. My car has finally stopped burping foam so I assume it is finally gone. On a Texas cold day I get heat pretty quickly but on a Texas hot day the A/C keeps up to about 90 degrees outside with the top down. It seems to work pretty darn good especially because the top is down most of the time. With that said my temperature typically gets to the zero in 180 within a few miles and stays there.