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Hi all,
I have a problem with the heater on my '97 993 Turbo - though I think that the issue would be identical on any 993 with aircon. There was a thread last Feb with "similar" problems but not identical ones, and the forum members were very helpful in getting to a solution - perhaps someone can point me in the right direction?
Unlike last Feb's problems, the heater servos on my car appear to function correctly - for those not familiar with the operation of their heater mechanism, when you change a setting on the heater panel on a 993/964 small electric motors (servos) operate to open and close flaps to direct air and change the mix of warm/cold air that flows into the passenger compartment. 1 (or 2?) servos open flaps to the footwells when the lower slider is moved to the right (servos located in front of the doors, apparently); another servo opens the flap to allow air to the screen when the top slider is to the right; and a further servo selects the airflow to be drawn from the passenger space or the air vent in the bonnet. I believe the other servos control the central ventilation vents (only in the circumstance described below) and the cold/warm air mix.
With the engine off it is possible to hear the motors operate and when the car is first started all seems well. The vents for the screen and footwells all may be opened/closed at will with the slider mechanism, and the fan operates as intended circulating air freely - and as directed to the screen/footwells/side vents. The defrost mechanism appears to function correctly (this simultaneously starts an additional fan in the engine compartment, opens the screen vents and closes all the others (including the central dash ones), turns on the a/c and switches the blower to full). The recirc/fresh air button also seems to function normally, evidenced by the warm air that circulates even when the temp control is turned right down with the fan on - only reverting to the air at the outside temperature when the recirc is turned off. The problems only seem to surface once the car has been running for a while.....
Basically the car slowly steams up; turning the blower to max doesn't really help - you can normally hear the blower trying to circulate air but it seems to cut in and out of it's own will, and even when apparently blowing reasonably hard the air onto the screen/side vents is weak suggesting the slider/servo mechanism to the servos is being over-ridden and they are remaining closed? Pressing the defrost button causes the usual much increased blower noise (suggesting the blower is being turned to max, over-riding whatever is causing it to ignore the commands from the blower control knob prior to this point) but often no flow to the screen follows. But then, sporadically, the screen vents are opened and air is blasted at the screen for a couple of seconds before they magically close again. All very odd. The only short-term solution I have is to press the recirc button, turn on the a/c (to dry the air) and turn the heater up - which produces satisfactory results but is obviously not ideal.
Overall, it would appear to me that there is a control unit somewhere that interprets the commands from the various controls - and that this is not functioning correctly. This would appear logical as the 993 has "climate control", so, for example, the temperature knob is not directly linked to the warm/cold air mixer but via a temperature sensor, and an instruction is issued to the servo to match the requirements with the sensed interior temperature.
Does anyone know the location of any such magical overall control device? Whether it is a "black-box" or repairable? Or had experince of these problems and know a solution if I am barking up the wrong tree?? Or am I to be a slave to my OPC and suffer what may well be a frightening bill?! My initial enquiry of my local one resulted in various theories - one of which might involve the draining and removal of the fuel tank which I'm sure will lighten my wallet dramatically!
Yours in hope,
Marcus Holden
I have a problem with the heater on my '97 993 Turbo - though I think that the issue would be identical on any 993 with aircon. There was a thread last Feb with "similar" problems but not identical ones, and the forum members were very helpful in getting to a solution - perhaps someone can point me in the right direction?
Unlike last Feb's problems, the heater servos on my car appear to function correctly - for those not familiar with the operation of their heater mechanism, when you change a setting on the heater panel on a 993/964 small electric motors (servos) operate to open and close flaps to direct air and change the mix of warm/cold air that flows into the passenger compartment. 1 (or 2?) servos open flaps to the footwells when the lower slider is moved to the right (servos located in front of the doors, apparently); another servo opens the flap to allow air to the screen when the top slider is to the right; and a further servo selects the airflow to be drawn from the passenger space or the air vent in the bonnet. I believe the other servos control the central ventilation vents (only in the circumstance described below) and the cold/warm air mix.
With the engine off it is possible to hear the motors operate and when the car is first started all seems well. The vents for the screen and footwells all may be opened/closed at will with the slider mechanism, and the fan operates as intended circulating air freely - and as directed to the screen/footwells/side vents. The defrost mechanism appears to function correctly (this simultaneously starts an additional fan in the engine compartment, opens the screen vents and closes all the others (including the central dash ones), turns on the a/c and switches the blower to full). The recirc/fresh air button also seems to function normally, evidenced by the warm air that circulates even when the temp control is turned right down with the fan on - only reverting to the air at the outside temperature when the recirc is turned off. The problems only seem to surface once the car has been running for a while.....
Basically the car slowly steams up; turning the blower to max doesn't really help - you can normally hear the blower trying to circulate air but it seems to cut in and out of it's own will, and even when apparently blowing reasonably hard the air onto the screen/side vents is weak suggesting the slider/servo mechanism to the servos is being over-ridden and they are remaining closed? Pressing the defrost button causes the usual much increased blower noise (suggesting the blower is being turned to max, over-riding whatever is causing it to ignore the commands from the blower control knob prior to this point) but often no flow to the screen follows. But then, sporadically, the screen vents are opened and air is blasted at the screen for a couple of seconds before they magically close again. All very odd. The only short-term solution I have is to press the recirc button, turn on the a/c (to dry the air) and turn the heater up - which produces satisfactory results but is obviously not ideal.
Overall, it would appear to me that there is a control unit somewhere that interprets the commands from the various controls - and that this is not functioning correctly. This would appear logical as the 993 has "climate control", so, for example, the temperature knob is not directly linked to the warm/cold air mixer but via a temperature sensor, and an instruction is issued to the servo to match the requirements with the sensed interior temperature.
Does anyone know the location of any such magical overall control device? Whether it is a "black-box" or repairable? Or had experince of these problems and know a solution if I am barking up the wrong tree?? Or am I to be a slave to my OPC and suffer what may well be a frightening bill?! My initial enquiry of my local one resulted in various theories - one of which might involve the draining and removal of the fuel tank which I'm sure will lighten my wallet dramatically!
Yours in hope,
Marcus Holden
