hvac system 88 930

[RJM3]

hello..on automatic hvac what controls the footwell fans I have a rotary dial in between seats but it doesn't seem to do much? Any help would be greatly appreciated...regards rjm3 Is there some type of sensor in the dash for the system?

[83930]

I don't know if this will help much but Here goes.
My 83 930 has auto heat control,which is the dial between the seats that says 0-def. that controls the heater temp.the fan knob on the dash next to the heater and defrost controls,take care of the fan speed. The air conditioning is controlled by the two knobs on the console above the shifter.The one on the left is temp and the one on the right is fan speed.I don't have a control for foot well just the dash and port under the dash by my feet,that the air comes out of.Hope this helps some... don't know for sure if the 83 and the 88 are the same but I think so.

[RJM3]

Thanks for the information..so the fan knob controls your footwell blowers? It sounds like you have the same system....I wonder what is so automatic about it? regards jerry>>>Anyone else can shed some light on the subject? When I had my car up on a lift the ducts go into a metal box on both sides and seem to have wiring to them???a mystery to me thanks again...

[83930]

The only thing that is automatic is the heat control.When you set your temp it will turn the fan on and off as needed to keep the temp at the setting that you use. I'm not sure of the manual system but think it works like the VW as a lever between the seats that you pull up to let heat in the car but it continues to blow air until you shut it off.The wiring that goes to the heater control boxes is a thermostat control.but I don't know for sure what it is for.There is one up by the rearview mirror that senses the interior temp but the one in the back by the heater boxes is still a mystery to me.It will go bad some day and then I will figure out what it does.

[RJM3]

thanks for all the information...maybe if it breaks i'll have to fix it? Anyone else could shed some light??much appreciated regards jerry

[Roland Kunz]

Hello

The heat controldevice has two heat sensors.

One on the driverside heat flap and one inside the cabin.
Pre 85 have a pssive unit at the mirror. 86- have a active ventet unit behind the dash using the little grille to vent the cabin air inside.

The device just works like other HAVC. You just set the ambienttemperature and that seting is fixed as master and the device trys to follow up regulating the temperature by trying to match the restistance from both sensors to equal level.

The "program" is on the little discrete device behind the driver side acces flap.

Over the years the system got a bit more complicatet using more external devices and working out different programshemata.

Later cars also use the engine sided fresh blower to cool down the heatexchangers/engine.

Your front blowers should jump in on the defrost position ( or max heat ) If not then check there fuses.

Grüsse