Air Conditioning Vents Help!
02-17-2003, 10:59 AM
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Air Conditioning Vents Help!
My Airconditioning vents blow no air even on Hi. I am looking for the correct "term" for the valve that controls the direction of air from the vents to defrost to footwells.
So I can do an educated search.
Anyone have experience with the "valve" being replaced, etc?
TIA
Best
Bob
So I can do an educated search.
Anyone have experience with the "valve" being replaced, etc?
TIA
Best
Bob
02-17-2003, 11:24 AM
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I had the same issue and it was casued by the fresh air adjustment module.
Part number for that part is 964 624 901 00, I paid $140 for parts and $100 had it repaired.
Part number for that part is 964 624 901 00, I paid $140 for parts and $100 had it repaired.
02-17-2003, 11:56 AM
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Good morning Bob,
A quick break down on how the HVAC system is set-up.
A total of 5 servos:
-2 servos--one for each side--for the temperature mixing valves for the mixing chambers. These servos are in the footwells for a 993, in the trunk (with the rest of the servos) for a 964.
-1 servo for footwell flap control.
-1 servo for the fresh air flap.
-1 servo controls the amount of air going to the center or defrost vents.
-The above three servos are in the back end of the trunk, beneath a black plastic tray.
A total of 4 fans (5 for a TT):
-Rear (or aux.) blower, left side of the engine compartment. Supplies forced heat when running, also helps cool the engine under certain circumstances. If the fan is seized, or its fuse blown, the interior fan will cut-out when temperature control is taken off "blue dot"--say, greater than 21C. The defroster will also cut out shortly after starting.
-Taking the interior fan control to >2 will cause the rear blower to switch to fast-speed, if heat is being requested (two speed fan).
-Left and right interior fans, in the luggage compartment. Infinite speed control, using the **** on the climate control unit (CCU).
-A small fan mounted to the CCU for measuring temperature.
964 owners have repaired/replaced many servos, looks like 993 owners are following right behind. <img border="0" title="" alt="[Wink]" src="wink.gif" /> Makes sense, as the systems are almost completely identical.
A quick break down on how the HVAC system is set-up.
A total of 5 servos:
-2 servos--one for each side--for the temperature mixing valves for the mixing chambers. These servos are in the footwells for a 993, in the trunk (with the rest of the servos) for a 964.
-1 servo for footwell flap control.
-1 servo for the fresh air flap.
-1 servo controls the amount of air going to the center or defrost vents.
-The above three servos are in the back end of the trunk, beneath a black plastic tray.
A total of 4 fans (5 for a TT):
-Rear (or aux.) blower, left side of the engine compartment. Supplies forced heat when running, also helps cool the engine under certain circumstances. If the fan is seized, or its fuse blown, the interior fan will cut-out when temperature control is taken off "blue dot"--say, greater than 21C. The defroster will also cut out shortly after starting.
-Taking the interior fan control to >2 will cause the rear blower to switch to fast-speed, if heat is being requested (two speed fan).
-Left and right interior fans, in the luggage compartment. Infinite speed control, using the **** on the climate control unit (CCU).
-A small fan mounted to the CCU for measuring temperature.
964 owners have repaired/replaced many servos, looks like 993 owners are following right behind. <img border="0" title="" alt="[Wink]" src="wink.gif" /> Makes sense, as the systems are almost completely identical.
02-17-2003, 01:52 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"> My Airconditioning vents blow no air even on Hi. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">I am assuming by this that all air is blowing out the floor heater vents? If so, I would suspect a vacuum leak; happened to me. On my '95 there is a vacuum control valve located on the very rear of the engine, along the heater intake duct. Mine was bad and I was losing vacuum; on climbing steep hills the AC vents would shut off. Gent on the downhill side and they'd open again as the car vacuuum overame the leak rate.
Might try looking at the vacuum lines comng from the rear vacuum canister (not sure where it is , but might be under the car) up to the AC dash system.
Might try looking at the vacuum lines comng from the rear vacuum canister (not sure where it is , but might be under the car) up to the AC dash system.
02-17-2003, 09:05 PM
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I just noticed my car does something similar. When I activate the interior fan, the fan runs as normal, but no air from any vents. When I activate the A/C, or Recirc. button, I get air instantly. Has one of these flapper servos quit on me?
02-17-2003, 10:54 PM
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The part # Robin referenced above is for the fresh air flap motor, likely the entire servo, not sure. I don't know how (or why) the fresh air flap would affect air flow through the center vents, but ... the HVAC system has other non-intuitive quirks, so who knows?
Checking the fresh air flap for proper operation couldn't be easier, no disassembly required. Simply listen at the fresh air intake (center, base of windshield) as you switch the recirculation button on/off. You should hear the air flow as it starts/stops.
You can scratch a little deeper by removing a flimsy plastic cover that stretches across the trunk, at the base of the windshield. Held in place by two screws and a rubber seal. Once the cover is removed, you should be able to see 3 of the 5 servos. By manipulating the climate control unit (CCU), you can watch the servos move. The fresh air intake servo is on/off (one extreme or the other), the other two (defrost/center vent and footwell flaps) should move with the sliders on the CCU.
Here's the vacuum controlled HVAC component, as referenced by Ray above:
<img src="http://members.rennlist.com/rgranaas/Vacuum%20Controlled%20Bypass.jpg" alt=" - " />
Us 964 owners are lucky, as we don't have one of these to complicate troubleshooting that is already complicated enough. I have no idea how this item works, or how a vacuum leak can cause it to affect (only!) air flow from the center vents. I'm looking forward to hearing from someone who can explain to me how this component fits in with the HVAC system.
Checking the fresh air flap for proper operation couldn't be easier, no disassembly required. Simply listen at the fresh air intake (center, base of windshield) as you switch the recirculation button on/off. You should hear the air flow as it starts/stops.
You can scratch a little deeper by removing a flimsy plastic cover that stretches across the trunk, at the base of the windshield. Held in place by two screws and a rubber seal. Once the cover is removed, you should be able to see 3 of the 5 servos. By manipulating the climate control unit (CCU), you can watch the servos move. The fresh air intake servo is on/off (one extreme or the other), the other two (defrost/center vent and footwell flaps) should move with the sliders on the CCU.
Here's the vacuum controlled HVAC component, as referenced by Ray above:
<img src="http://members.rennlist.com/rgranaas/Vacuum%20Controlled%20Bypass.jpg" alt=" - " />
Us 964 owners are lucky, as we don't have one of these to complicate troubleshooting that is already complicated enough. I have no idea how this item works, or how a vacuum leak can cause it to affect (only!) air flow from the center vents. I'm looking forward to hearing from someone who can explain to me how this component fits in with the HVAC system.
