HVAC Blower Quit
10-05-2007, 10:11 PM
#17
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Malcolm - on the '94 & '95 cars the '0' speed is actually truly a blower off - you are right - on earlier cars the blower always runs in '0' mode - just very slowly.
However on some older models there was an 'off 'position in the flap slider that was a 'whole system off mode'. Later systems - even the 94+ in zero speed mode - will always run & in fresh air mode the airflow at speed can be enough to AC cool or heat the cabin w/ no fan.
Alan
However on some older models there was an 'off 'position in the flap slider that was a 'whole system off mode'. Later systems - even the 94+ in zero speed mode - will always run & in fresh air mode the airflow at speed can be enough to AC cool or heat the cabin w/ no fan.
Alan
10-05-2007, 11:01 PM
#18
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Thx for the clarification Alan.
I have read and reread the the WSM re. which flap open/closed fan on /off and still find some aspects confusing.
As mentioned before a more modern simplistic version with electronic action could be designed. I want to think the servos from my RC helicopter can suffice............big winter project.
I have read and reread the the WSM re. which flap open/closed fan on /off and still find some aspects confusing.
As mentioned before a more modern simplistic version with electronic action could be designed. I want to think the servos from my RC helicopter can suffice............big winter project.
10-06-2007, 06:36 PM
#19
Race Director
Very interesting......so the HVAC blower will run through the defroster relay when set to max defrost.....BUT does it still run through the resistor pack?? If I remember correctly (always a challenge) there only is only 1 wire (+-) going to the fan from the resistor....I'll have to look at my pics....
10-06-2007, 07:02 PM
#20
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Brian,
It bypasses the resistor pack & so does the switch in speed 4.
Its actually a defogger relay - many are confused (Porsche even) it is not the best way to defrost a windsheild since it also turns on the AC. The defroster vent position and max heating is the best way to defrost.
Alan
It bypasses the resistor pack & so does the switch in speed 4.
Its actually a defogger relay - many are confused (Porsche even) it is not the best way to defrost a windsheild since it also turns on the AC. The defroster vent position and max heating is the best way to defrost.
Alan
10-06-2007, 11:26 PM
#21
Race Director
Alan
That makes sense about speed 4 (full current no steps down to reduce speed).....but I thought the idea on max defrost was to de-humidify the air at the same time you were heating it...which makes the defroster work better.......how much better...I dunno...but it seems like a good idea....maybe the heating aspects of the heater more than offset the humidity reducing aspects of the A/C.....
That makes sense about speed 4 (full current no steps down to reduce speed).....but I thought the idea on max defrost was to de-humidify the air at the same time you were heating it...which makes the defroster work better.......how much better...I dunno...but it seems like a good idea....maybe the heating aspects of the heater more than offset the humidity reducing aspects of the A/C.....
10-09-2007, 09:51 PM
#22
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Brian
For defogging (water vapor on the inside of the screen) Yes - thats why the AC is on...
For defrosting (de-icing the outside of the screen) its usually not much required. When its very cold if you heat the air it can hold more water and the windshield should not cool the air below where it was at ambient anyway - so it should not precipitate on the glass... (however your hot wet breath may to some degree..)
However the reduction in heat from having the AC on full (and the risk it may ice up the evaporator reducing airflow) make this much slower at defrosting....
Even if there is any associated fogging - its better to fully defrost first (The ^ mode & max heating) - then switch to defog at the end since it only takes a few seconds to effectively defog.
Again its really a DEFOG mode - Porsche and many others seem to use the terms defrost & defog interchangeably - they really are ideally different modes - even if many cars only identify one.
Alan
For defogging (water vapor on the inside of the screen) Yes - thats why the AC is on...
For defrosting (de-icing the outside of the screen) its usually not much required. When its very cold if you heat the air it can hold more water and the windshield should not cool the air below where it was at ambient anyway - so it should not precipitate on the glass... (however your hot wet breath may to some degree..)
However the reduction in heat from having the AC on full (and the risk it may ice up the evaporator reducing airflow) make this much slower at defrosting....
Even if there is any associated fogging - its better to fully defrost first (The ^ mode & max heating) - then switch to defog at the end since it only takes a few seconds to effectively defog.
Again its really a DEFOG mode - Porsche and many others seem to use the terms defrost & defog interchangeably - they really are ideally different modes - even if many cars only identify one.
Alan
10-09-2007, 10:17 PM
#23
Race Director
Alan
Okay no I understand......kinda like to two function rear "defroster"..... I don't remember which one is which..but one mode is a twist the other is a push...
Okay no I understand......kinda like to two function rear "defroster"..... I don't remember which one is which..but one mode is a twist the other is a push...
10-10-2007, 01:21 AM
#24
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As usual, Alan is correct.
Swapped the horn relay with the fresh air blower relay. Blower and AC work normally again.
Need to buy a replacement horn relay now. Love that kinda repair, baby!
Swapped the horn relay with the fresh air blower relay. Blower and AC work normally again.
Need to buy a replacement horn relay now. Love that kinda repair, baby!
10-10-2007, 05:49 PM
#29
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Brian
For defogging (water vapor on the inside of the screen) Yes - thats why the AC is on...
For defrosting (de-icing the outside of the screen) its usually not much required. When its very cold if you heat the air it can hold more water and the windshield should not cool the air below where it was at ambient anyway - so it should not precipitate on the glass... (however your hot wet breath may to some degree..)
However the reduction in heat from having the AC on full (and the risk it may ice up the evaporator reducing airflow) make this much slower at defrosting....
Even if there is any associated fogging - its better to fully defrost first (The ^ mode & max heating) - then switch to defog at the end since it only takes a few seconds to effectively defog.
Again its really a DEFOG mode - Porsche and many others seem to use the terms defrost & defog interchangeably - they really are ideally different modes - even if many cars only identify one.
Alan
For defogging (water vapor on the inside of the screen) Yes - thats why the AC is on...
For defrosting (de-icing the outside of the screen) its usually not much required. When its very cold if you heat the air it can hold more water and the windshield should not cool the air below where it was at ambient anyway - so it should not precipitate on the glass... (however your hot wet breath may to some degree..)
However the reduction in heat from having the AC on full (and the risk it may ice up the evaporator reducing airflow) make this much slower at defrosting....
Even if there is any associated fogging - its better to fully defrost first (The ^ mode & max heating) - then switch to defog at the end since it only takes a few seconds to effectively defog.
Again its really a DEFOG mode - Porsche and many others seem to use the terms defrost & defog interchangeably - they really are ideally different modes - even if many cars only identify one.
Alan
10-10-2007, 05:57 PM
#30
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In Phoenix, the only time there might be windscreen fog is during a rainstorm when the fog forms on the -outside- of the cold glass. And the AC is -always- on there it seems.
IMHO, Phoenix has a wonderful climate between October and early May. Those other few months, you leave the car running in the paring lot, locked and with the AC on full. So you don't burn your hands on the steering wheel when you get back in. Karen wants to buy a place there as a retirement stop. OK I said if I can have a place in the Sierras (again...) for the non-winter months. Still negotiating on that one.
IMHO, Phoenix has a wonderful climate between October and early May. Those other few months, you leave the car running in the paring lot, locked and with the AC on full. So you don't burn your hands on the steering wheel when you get back in. Karen wants to buy a place there as a retirement stop. OK I said if I can have a place in the Sierras (again...) for the non-winter months. Still negotiating on that one.