Blower Motor
11-14-2001, 01:35 AM
#1
Burning Brakes
Thread Starter
Blower Motor
O.K. Just one more dumb question today and I'll give up. When I turn the ignition switch on the blower motor in the engine compartment is always on. The air always blows a little in the passenger compartment too. I assume that this is the same air blowing from the motor. You can of course make it cold or hot depending on the rotary dial. On all other P-cars I've owned that heater motor came on only when you turned the heat on. Is that thing suppose to run all the time?
Thanks again.
John
Thanks again.
John
11-14-2001, 08:58 PM
#3
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Hi John,
Suppose I can take a stab at this (our resident rear blower expert is Adrian).
My rear blower only comes on when the climate control dial is set to a certain temperature--say, about in the middle. It doesn't run when on the cooler settings.
The interior fan speed has no effect on rear cooler fan operation.
I believe the above to be normal operation.
The rear blower can also be activated to cool the engine.
So, the rear blower shouldn't be running all the time. I'm guessing one of your sensors is sending a bad signal, or your relay may have a problem.
The rear blower relay is the same as used for the oil cooler and A/C condenser fans. Try swapping them around and see if that stops your rear blower from running all the time.
BTW, your A/C condenser fan should come on with the A/C, ignition on. If it doesn't, you have a problem somewhere--e.g., the fuse, relay or resistor.
Good luck!
Suppose I can take a stab at this (our resident rear blower expert is Adrian).
My rear blower only comes on when the climate control dial is set to a certain temperature--say, about in the middle. It doesn't run when on the cooler settings.
The interior fan speed has no effect on rear cooler fan operation.
I believe the above to be normal operation.
The rear blower can also be activated to cool the engine.
So, the rear blower shouldn't be running all the time. I'm guessing one of your sensors is sending a bad signal, or your relay may have a problem.
The rear blower relay is the same as used for the oil cooler and A/C condenser fans. Try swapping them around and see if that stops your rear blower from running all the time.
BTW, your A/C condenser fan should come on with the A/C, ignition on. If it doesn't, you have a problem somewhere--e.g., the fuse, relay or resistor.
Good luck!
11-14-2001, 10:25 PM
#4
John:
I just spoke to my Porsche mechanic on the air that blows in the passenger compartment a couple of weeks ago. In a 964, there is always air moving through the ventilation system regardless of the fan speed setting. In other words, if you have the fan speed **** set to zero, air still will come out of the dash vents (or floor or windshield areas).
For the least amount of air movement in the cabin, set the dash fan speed **** to zero and set the temperature control to the 'blue dot' position (**** turned all the way counter clockwise). Air will move faster (fan speeds will increase) once the **** is turned past the blue dot even though the fan is still set to zero.
Hope this helps a little.
Jay
90 964
I just spoke to my Porsche mechanic on the air that blows in the passenger compartment a couple of weeks ago. In a 964, there is always air moving through the ventilation system regardless of the fan speed setting. In other words, if you have the fan speed **** set to zero, air still will come out of the dash vents (or floor or windshield areas).
For the least amount of air movement in the cabin, set the dash fan speed **** to zero and set the temperature control to the 'blue dot' position (**** turned all the way counter clockwise). Air will move faster (fan speeds will increase) once the **** is turned past the blue dot even though the fan is still set to zero.
Hope this helps a little.
Jay
90 964
11-15-2001, 04:50 AM
#5
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Dear Slant,
There are two fans in possible action here. (I am assuming the two foward blower fans are not selected)
1/. If the temp control **** is outside the blue dot position (normally around 21 to 24 but it varies from 964 to 964) the blower fan will crank up to low speed and stay on whilst power is applied.
2/. There is also a fan at the rear of the control unit blowing air over the sensor.
The statement that air will always flow is quite correct. The only way to stop this is to shut all the vents.
If the fan is working in the blue dot position this means that most likely the blower fan speed control relay is stuck in the low speed position. The blower fan is very important for engine cooling as well. This is why it is also called the additional engine cooling fan.
The heating or Klima system in heating mode is automatic. As soon as you turn the temp control **** out of the blue dot position you have activated the heating system,
Ciao,
Adrian
911C4
There are two fans in possible action here. (I am assuming the two foward blower fans are not selected)
1/. If the temp control **** is outside the blue dot position (normally around 21 to 24 but it varies from 964 to 964) the blower fan will crank up to low speed and stay on whilst power is applied.
2/. There is also a fan at the rear of the control unit blowing air over the sensor.
The statement that air will always flow is quite correct. The only way to stop this is to shut all the vents.
If the fan is working in the blue dot position this means that most likely the blower fan speed control relay is stuck in the low speed position. The blower fan is very important for engine cooling as well. This is why it is also called the additional engine cooling fan.
The heating or Klima system in heating mode is automatic. As soon as you turn the temp control **** out of the blue dot position you have activated the heating system,
Ciao,
Adrian
911C4
11-15-2001, 01:47 PM
#6
Burning Brakes
Thread Starter
So if I understand you all correctly the fan in the engine compartment should NOT run all the time? But, there is always airflow in the passenger area?
11-15-2001, 03:44 PM
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Hi John,
The constant airflow is provided by the interior fan. For example, my interior fan still runs, even with the fan set to the furthermost counter-clockwise setting.
Ironically, about a year ago I had a mechanic tell me that I needed a new climate control unit, because my interior fan would not turn off completely. I always thought this was normal, and Jay's post confirms that it is.
The rear blower only provides your heat (and engine cooling) ... its output goes to the heat exchangers. You can look up the configuration on your PET.
The constant airflow is provided by the interior fan. For example, my interior fan still runs, even with the fan set to the furthermost counter-clockwise setting.
Ironically, about a year ago I had a mechanic tell me that I needed a new climate control unit, because my interior fan would not turn off completely. I always thought this was normal, and Jay's post confirms that it is.
The rear blower only provides your heat (and engine cooling) ... its output goes to the heat exchangers. You can look up the configuration on your PET.
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11-15-2001, 07:27 PM
#8
Racer
High,
I do have air blowing through all the time, BUT, when I have the heat set on, and the fan high it stops blowing hot air down by my feet once in a while and will start up again, I always remember this thing blowing constantly, could I be in need of a new fan motor? Or am I showing signs of my age w/ memory loss?
Thanx for info..
I do have air blowing through all the time, BUT, when I have the heat set on, and the fan high it stops blowing hot air down by my feet once in a while and will start up again, I always remember this thing blowing constantly, could I be in need of a new fan motor? Or am I showing signs of my age w/ memory loss?
Thanx for info..
11-15-2001, 10:12 PM
#9
Track Day
Hi John,
Definitely not an expert, but I'll add another $.02 worth. As several have said, the rear blower fan serves a dual purpose, interior HEATING (not A/C) air, and engine cooling flow. For engine cooling, the fan MAY run (actually should run) with high engine compartment temps, even with the car totally off. It tends to cycle on and off until temp is down. In fact over-running of this (faulty temp sensor I suspect) has at times been a culprit for dead battery symptoms. Does yours run with car off? Is it possible that the temp sensor in engine compartment is causing it to run all the time? Dont mean to throw a red herring into the thread.
My rear blower doesnt seem to be on enough to sense it at all times. With increased temp on climate control, interior air flow will increase either by cranking the temp control up full OR by selecting increased fan flow. Slides, as always, help direct to floor or defrost vents. A/C vents (warm air) seem to be on at all times with higher temp control engaged.
Dont you love the exact science of p-car operations!
good luck,
Monty Willis
92 C2 Cab
(no rain in P-cola Fl for well over a month,
top has never been up!)
Definitely not an expert, but I'll add another $.02 worth. As several have said, the rear blower fan serves a dual purpose, interior HEATING (not A/C) air, and engine cooling flow. For engine cooling, the fan MAY run (actually should run) with high engine compartment temps, even with the car totally off. It tends to cycle on and off until temp is down. In fact over-running of this (faulty temp sensor I suspect) has at times been a culprit for dead battery symptoms. Does yours run with car off? Is it possible that the temp sensor in engine compartment is causing it to run all the time? Dont mean to throw a red herring into the thread.
My rear blower doesnt seem to be on enough to sense it at all times. With increased temp on climate control, interior air flow will increase either by cranking the temp control up full OR by selecting increased fan flow. Slides, as always, help direct to floor or defrost vents. A/C vents (warm air) seem to be on at all times with higher temp control engaged.
Dont you love the exact science of p-car operations!
good luck,
Monty Willis
92 C2 Cab
(no rain in P-cola Fl for well over a month,
top has never been up!)
11-16-2001, 03:50 AM
#10
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Guys,
In default or with nothing selected mode the fresh air servo valve is open. Allowing the flow of air at all times. Once you select something, any function on the controller this valve can be left open, closed or modulated depending upon how much outside air is needed. There are five servo valves, each has their own function and combined with others, other functions.
The blower fan in high speed mode will cycle on and off very quickly. It is often heard running for just a few seconds after you start with ahot engine. This is to clear the hot static air around the engine.
Under normal running conditions and with everything else working the blower fan will never be heard at high speed. If you are stiuck in traffic and the engine is heating up, crank the heater up to full red dot. This will help cool the engine.
The airconditioning and heating system in the 964 is very complex and needs quite a lot of explanation.
Ciao,
Adrian
911C4
PS: If you engine gets really hot whilst stopped. The Blower fan will crank up. This is why it is important to
a). Make sure you have the new blower resistor installed (was a recall in the USA) and
b). Make sure your blower fan is in good condition.
In default or with nothing selected mode the fresh air servo valve is open. Allowing the flow of air at all times. Once you select something, any function on the controller this valve can be left open, closed or modulated depending upon how much outside air is needed. There are five servo valves, each has their own function and combined with others, other functions.
The blower fan in high speed mode will cycle on and off very quickly. It is often heard running for just a few seconds after you start with ahot engine. This is to clear the hot static air around the engine.
Under normal running conditions and with everything else working the blower fan will never be heard at high speed. If you are stiuck in traffic and the engine is heating up, crank the heater up to full red dot. This will help cool the engine.
The airconditioning and heating system in the 964 is very complex and needs quite a lot of explanation.
Ciao,
Adrian
911C4
PS: If you engine gets really hot whilst stopped. The Blower fan will crank up. This is why it is important to
a). Make sure you have the new blower resistor installed (was a recall in the USA) and
b). Make sure your blower fan is in good condition.
11-16-2001, 12:17 PM
#11
Burning Brakes
Thread Starter
Well now you got me worried again. Thought I had it all cleared up. You say there was a recall of a resistor. How do I tell if it's been updated? Where is this resistor?
11-16-2001, 06:26 PM
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Just FYI .... the owner's manual has a pretty good description of the HVAC system's operation.
For example, it states: "At the '0' setting the fan runs at minimum speed." Notice it says minimum speed--not off.
Page 56 of my '91 manual.
For example, it states: "At the '0' setting the fan runs at minimum speed." Notice it says minimum speed--not off.
Page 56 of my '91 manual.
11-16-2001, 07:36 PM
#13
Burning Brakes
Thread Starter
Randall,
Thanks. I picked up on that just last night in my owners manual. I was reviewing it to make sure the operation is correct.
Thanks again.
BTW - I love this damn PET thing. Really neat info.
Thanks. I picked up on that just last night in my owners manual. I was reviewing it to make sure the operation is correct.
Thanks again.
BTW - I love this damn PET thing. Really neat info.
11-16-2001, 08:46 PM
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And speaking of PET ... the rear blower motor w/resistor = item #10. When the recall was performed on my car, I got rev. #2 of the resistor = 964-616-550-02.
So, if you can find part #964-616-550-02 on the resistor somewhere, you have the recall resistor.
So, if you can find part #964-616-550-02 on the resistor somewhere, you have the recall resistor.
11-18-2001, 10:59 PM
#15
Track Day
Folks,
Just another quick fyi on this topic. I've replaced 2 of these motors and have found an interesting quirk with the "system" back there. Both of my replacements have been with used motors that checked "bad" with the hammer while installed in cars. It took my second replacement before I discovered (I believe) at least part of the gremlin.
The harder plastic housing, called the hot air socket, part #1 in the PET above, MAY, actually deform the housing on the fan motor housing (#11 above), when attached. The fan blades fit in the housing with very close tolerance. I had a motor when it was uninstalled, the blades swung freely, with no binding, and when hooked up electrically, blew great. In the process of screwing the hot air socket as they call it, to the motor housing, it actually deformed the housing and caused it to bind the fan blades. I suppose the harder plastic of the socket may have deformed a little from new due to heating in the rear compartment, and the attachment point was no longer perfectly flat. A little shaving to the socket (and just a little to the fan housing, solved the problem. If you've had a problem with noise, failing fans, or fuses, this may be a source of the problem. Of course over time the rubbing will cause failure of the bearings or motor. The second one, with mods, has been in quite a while now, with no problems.
Monty Willis
92 C2 Cab
Just another quick fyi on this topic. I've replaced 2 of these motors and have found an interesting quirk with the "system" back there. Both of my replacements have been with used motors that checked "bad" with the hammer while installed in cars. It took my second replacement before I discovered (I believe) at least part of the gremlin.
The harder plastic housing, called the hot air socket, part #1 in the PET above, MAY, actually deform the housing on the fan motor housing (#11 above), when attached. The fan blades fit in the housing with very close tolerance. I had a motor when it was uninstalled, the blades swung freely, with no binding, and when hooked up electrically, blew great. In the process of screwing the hot air socket as they call it, to the motor housing, it actually deformed the housing and caused it to bind the fan blades. I suppose the harder plastic of the socket may have deformed a little from new due to heating in the rear compartment, and the attachment point was no longer perfectly flat. A little shaving to the socket (and just a little to the fan housing, solved the problem. If you've had a problem with noise, failing fans, or fuses, this may be a source of the problem. Of course over time the rubbing will cause failure of the bearings or motor. The second one, with mods, has been in quite a while now, with no problems.
Monty Willis
92 C2 Cab