996 heater not working
Discussion
Hi, I hope somebody can help.I have just bought myself a 1998 996 Carrera S. The fan heater only works on initial starting of the engine from cold and will continue to work all the time the car is running. The problem occurs when I turn off the engine and then start the engine up again the fan heater doesn't work. The controls on the dash all work fine but no air blows, hot or cold. Any ideas..Thanks Enzo996
enzo996 said:
Hi, I hope somebody can help.I have just bought myself a 1998 996 Carrera S. The fan heater only works on initial starting of the engine from cold and will continue to work all the time the car is running. The problem occurs when I turn off the engine and then start the engine up again the fan heater doesn't work. The controls on the dash all work fine but no air blows, hot or cold. Any ideas..Thanks Enzo996
The following might work on your '99....The AC Climatronic unit is actually manufactured by Audi. There is some sort of serial data stream (not CAN) that allows the AC unit to display engine parameters. Works on early 996s and boxters.
To switch from F to C:
Hold down the recirculating button then push both the temperature + - buttons.
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. .
5c - Outside temp. (matches 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?
OK, I went through the procedure explained by Rockster but don't know what to look for to see why the fan heater only works when the car starts up from cold and will continue to work the whole of the time the car is running. If I turn the ignition off and then start her up again the heater doesn't work so I end up with steamy windscreen and windows.
enzo996 said:
OK, I went through the procedure explained by Rockster but don't know what to look for to see why the fan heater only works when the car starts up from cold and will continue to work the whole of the time the car is running. If I turn the ignition off and then start her up again the heater doesn't work so I end up with steamy windscreen and windows.
Just to be clear that was no procedure I posted just some diagnostics that one can call up.Since none of my cars supports this I have not been able to experiment and have no real experience to share.
One thought is if the heater works ok when you start the car from cold but doesn't if you turn the engine off then restart is don't do the last part. Don't turn the engine off after you start it until you are at your destination.
Steamy windows and windscreen suggests water drains are plugged up and water has accumulated under the panels under the front trunk lid. You probably should check the water drains to be sure they are free of trash and water drains without any problems.
If the drains are free of trash and dry then IIRC when I turn on my car on some humid days the windows can steam up until I turn on the A/C. This dries the air coming into the cabin and removes steam or water vapor from the inside of the glass very quickly. The heater alone will not do this nearly as fast and in fact it can make things worse for a while until the coolant warms up some.
The steam build up can be worse if I failed to remember to run the heater system with the A/C off for a few minutes to dry the evaporator which can in real humid conditions get real wet as water condenses on its colder surfaces.
Yet another thought is that perhaps that the A/C compressor doesn't come back on the 2nd engine start is normal for your car?
With my 02 Boxster and 03 Turbo with their auto climate heater/AC system if I turn off the engine with the A/C on (the snowflake symbol lit) and then restart the engine the A/C compressor is on at the 2nd and subsequent engine start.
Assuming your car doesn't have auto climate control perhaps with your car and its manual A/C system the A/C compressor does not remain on after an engine shutoff? IOWs, this is normal behavior? The car's owners manual could shed some light on this.
If A/C compressor should come back on after an engine shutoff/restart but does not this could be a sign the A/C system is in need of attention.
Perhaps the system is low on refrigerant and the system leaves the compressor off to prevent damage? If no refrigerant there is no cooling but there is also no flow of oil through the system and this can ruin an otherwise good compressor.
If the diagnostics I posted before is of no help to you then you probably should seek out an experienced A/C shop and have the car's A/C system looked into.
If the water drains are dry and there is no sign of water in the cabin the odds are the problem is beyond your abilty to address.
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