Discussion
Hi all,
Ive recently read on the owners page that someone had heater probs due to the vacuum not working properly, thus not opening the right vent (or something).. i think i may have the same prob and im a bit worried about the wife in winter!
Any help as to how i can diagnose my problem (the car not the wife!) would be greatly appreciated
Brett 86 S3
Ive recently read on the owners page that someone had heater probs due to the vacuum not working properly, thus not opening the right vent (or something).. i think i may have the same prob and im a bit worried about the wife in winter!
Any help as to how i can diagnose my problem (the car not the wife!) would be greatly appreciated
Brett 86 S3
I posted this last year to the turbo list when someone was having heater problems. A heater is a must in the frozen north of Minnesota. KFM was going to edit, clip, and paste it into the EFF when he had a chance.
Okay I will try and explain the heater controls and function.
The right knob controls the air distribution. It controls a series of flaps to divert air to the correct vents. Full clockwise of this knob
will recirculate cabin air this is handy if going for max A/C cooling. As you move this knob closer to the 1 o'clock position the external air flap opens until full outside air is drawn in. These positions are used in the A/C mode or for straight cabin air exchange and air is directed through all dash vents. As you move the knob to the 11 o'clock position the flaps will close the two dash vents closest to the center backbone, it re-routes the air flow through the heater core instead of A/C core and the air flow will be diverted to the footwell tube ducts and a touch to the front windscreen vents. As you turn the knob towards full counter clockwise more of the air
flow will be diverted from the footwells to the windscreen till all of the air flow is directed to the windscreen defroster. The two small center knobs you know about already A/C and fan speed.
The left knob is temperature control for the heater core, full clockwise the core is not open to the hot water. Full counter clockwise and it's full heater flow of hot water. A cable connected the temperature knob (left knob) attaches to the water flow valve to control coolant flow through the heater core.
The right knob is connected to a control cam that rotates to press down two plungers on air valves that the vacumm lines are attached to with a variety of T's and rubber elbows. The left air valve by regulating the amount of vacumm, controls the air intake flap actuator mounted on the blower box under the front bonnet. The right air valve controls the mode flap actuator that diverts air through either the heater core or A/C and also enables/disables the two vents closest the backbone. A steel rod connected to the cam controls the air flow between the footwell
plastic tube ducts and the windscreen vents. The two outside dash vents should be closed off with the thumbwheels when heating or defrosting as they continue to pump cold air as they bypass the
heater core. At no time will they ever pump warm air. It is not nessesary to close off the two center dash vents with the thumbwheels as when the heat is on they will be automatically closed.
Also a vac lines and a T are in cars with a mechanical vac pump are under the left tank cover in the engine compartment.
Hope this helps as this is as detailed as it gets.
Not a very good A/C or heater design but I don't think anyone looking at car magazines as a youth said "One day I'm gonna get me one those cars with a really neat HVAC system".
Calvin 90 SE
Okay I will try and explain the heater controls and function.
The right knob controls the air distribution. It controls a series of flaps to divert air to the correct vents. Full clockwise of this knob
will recirculate cabin air this is handy if going for max A/C cooling. As you move this knob closer to the 1 o'clock position the external air flap opens until full outside air is drawn in. These positions are used in the A/C mode or for straight cabin air exchange and air is directed through all dash vents. As you move the knob to the 11 o'clock position the flaps will close the two dash vents closest to the center backbone, it re-routes the air flow through the heater core instead of A/C core and the air flow will be diverted to the footwell tube ducts and a touch to the front windscreen vents. As you turn the knob towards full counter clockwise more of the air
flow will be diverted from the footwells to the windscreen till all of the air flow is directed to the windscreen defroster. The two small center knobs you know about already A/C and fan speed.
The left knob is temperature control for the heater core, full clockwise the core is not open to the hot water. Full counter clockwise and it's full heater flow of hot water. A cable connected the temperature knob (left knob) attaches to the water flow valve to control coolant flow through the heater core.
The right knob is connected to a control cam that rotates to press down two plungers on air valves that the vacumm lines are attached to with a variety of T's and rubber elbows. The left air valve by regulating the amount of vacumm, controls the air intake flap actuator mounted on the blower box under the front bonnet. The right air valve controls the mode flap actuator that diverts air through either the heater core or A/C and also enables/disables the two vents closest the backbone. A steel rod connected to the cam controls the air flow between the footwell
plastic tube ducts and the windscreen vents. The two outside dash vents should be closed off with the thumbwheels when heating or defrosting as they continue to pump cold air as they bypass the
heater core. At no time will they ever pump warm air. It is not nessesary to close off the two center dash vents with the thumbwheels as when the heat is on they will be automatically closed.
Also a vac lines and a T are in cars with a mechanical vac pump are under the left tank cover in the engine compartment.
Hope this helps as this is as detailed as it gets.
Not a very good A/C or heater design but I don't think anyone looking at car magazines as a youth said "One day I'm gonna get me one those cars with a really neat HVAC system".
Calvin 90 SE
Thanks also for the detailed discussion. On my '90SE the air wouldn't go to the windscreen. I found a T under the driverside dash with only two vacuum lines on it. When I plugged the open port, everything seemed to work fine. So I left well enough alone. Any thoughts as to what should have been hooked to the open port?
Thanks
Bill
Thanks
Bill
Calvin said:
The left knob is temperature control for the heater core, full clockwise the core is not open to the hot water. Full counter clockwise and it's full heater flow of hot water. A cable connected the temperature knob (left knob) attaches to the water flow valve to control coolant flow through the heater core.
Great info here! A bit of a hijack though... I had posed a question about my free-spinning tempurature control a few weeks back, figured I'd follow up with it here while we're on the subject.
I was able to pop out my radio and follow this green cable (green in a 95 S4s) from the tempurature control dial up into the void of the dash. Where abouts is the water flow valve that the other end of this cable eventually attaches to? I guess that would be the heater core - is that in the engine compartment or buried up under the dash? I'd like to be able to check that end to see if that's my point of failure.
Thanks!
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