Interior fan only works with AC on(79 SC)
07-21-2008, 02:07 PM
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Interior fan only works with AC on(79 SC)
The only time I can get my fan to come on is when I turn the AC on!
Does the dash mounted switch fail , I don't even see one for sale on Pelican.
Is there a simplified circuit diagram available that shows how this is switch works!
Also how does the switch come out of the dash ?
The fan obviously works fine withthe AC
In fact can some one explain the whole system including the engine blower in simple electrical terms i.e. what controls what .I realise that the switches between the seats turn on the engine blower but are they intelocked? I just can't get any cool air into the car without A/C
Any help appreciated.
TIA
Does the dash mounted switch fail , I don't even see one for sale on Pelican.
Is there a simplified circuit diagram available that shows how this is switch works!
Also how does the switch come out of the dash ?
The fan obviously works fine withthe AC
In fact can some one explain the whole system including the engine blower in simple electrical terms i.e. what controls what .I realise that the switches between the seats turn on the engine blower but are they intelocked? I just can't get any cool air into the car without A/C
Any help appreciated.
TIA
07-21-2008, 03:31 PM
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One of the most confusing elements of the SC is the interior comfort system(s). I'll try to help.
1) Center heater pulls next to hand-brake operate the heater blower motor("engine blower" as you call it) and air duct valves. Pulling the cable levers opens the butterfly valves that pass the hot air from heat-exchangers into the car's interior and turns on the heater-blower motor. Each cable opens 1 valve, and you have one valve on each side of the car/engine. Thus, it's possible to open one heater line and keep the other closed (ie: passenger only; driver only).
2) Climate control/defroster levers on the center of the dash open fresh air from the little slot-vent in the hood and direct the air to either your feet, or the dash/windshield, and operates the fresh air fan that pushes said air. There are three *****. Far left closes vent and turns off the fresh air fan. Top **** opens vents and at mid-throw initiates fan to one of three speeds. Middle **** directs fresh air direction inside car. Far left sends air to the feet; midway sends air to widnshield and feet; far right sends all fresh air to windshield. Bottom lever works with the heater lines from center heater levers (next to hand brake) for hot defrost. To get hot defrost: pull heater levers up and push bottom dash switch (Red color I think) all the way to the right. The hot air is diverted into fresh-air ducting and on to windshield.
3) Air conditioner/dash-vent blower motor is operated by the air conditioner switches located on the center console, in front of the gear shift lever. The A/C switch operates the three-speed fan that blows air from the small dash vents, AND actuates the A/C compressor/front condensor fan. The only way to get air from the dash vents is with the A/C fan and associated switch ... which actuates the A/C compresor. Now, if you're compressor is blown, or your freon/R134 is low/out, there is a way to get fresh "unconditioned" air to blow from the center-dash vents: go to the A/C compressor in the engine and disconnect the lead wire(s) from the compressor clutch. When you turn on the A/C switch, the blower motor for air over the evaporator will still blow air ... ambient tempurature ... and initiate the front condensor motor (not harmful) and the compressor will remain off. You'll have fresh air blowing on you from the dash vents. (Like anywhere else, if you disconnect any leads, cover them [electrician's tape, shrink-tubing, etc] and secure them safely in the engine bay to avoid accidental grounding.)
tip: if your Climate Control fresh-air blower (dash switches than slide left to right) isn't working, after checking all fuses and relays, us a 12-volt battery and temporary leads to check the blower motor in the system (it's that big black lump of tubes and cables under the windshield and behind that cardboard piece). If the blower motor is out, carefully remove it and get a replacement at the salvage yard.
My fresh air blower motor burned out and I replaced mine for $50.00 and my own labor.
Good luck!!
1) Center heater pulls next to hand-brake operate the heater blower motor("engine blower" as you call it) and air duct valves. Pulling the cable levers opens the butterfly valves that pass the hot air from heat-exchangers into the car's interior and turns on the heater-blower motor. Each cable opens 1 valve, and you have one valve on each side of the car/engine. Thus, it's possible to open one heater line and keep the other closed (ie: passenger only; driver only).
2) Climate control/defroster levers on the center of the dash open fresh air from the little slot-vent in the hood and direct the air to either your feet, or the dash/windshield, and operates the fresh air fan that pushes said air. There are three *****. Far left closes vent and turns off the fresh air fan. Top **** opens vents and at mid-throw initiates fan to one of three speeds. Middle **** directs fresh air direction inside car. Far left sends air to the feet; midway sends air to widnshield and feet; far right sends all fresh air to windshield. Bottom lever works with the heater lines from center heater levers (next to hand brake) for hot defrost. To get hot defrost: pull heater levers up and push bottom dash switch (Red color I think) all the way to the right. The hot air is diverted into fresh-air ducting and on to windshield.
3) Air conditioner/dash-vent blower motor is operated by the air conditioner switches located on the center console, in front of the gear shift lever. The A/C switch operates the three-speed fan that blows air from the small dash vents, AND actuates the A/C compressor/front condensor fan. The only way to get air from the dash vents is with the A/C fan and associated switch ... which actuates the A/C compresor. Now, if you're compressor is blown, or your freon/R134 is low/out, there is a way to get fresh "unconditioned" air to blow from the center-dash vents: go to the A/C compressor in the engine and disconnect the lead wire(s) from the compressor clutch. When you turn on the A/C switch, the blower motor for air over the evaporator will still blow air ... ambient tempurature ... and initiate the front condensor motor (not harmful) and the compressor will remain off. You'll have fresh air blowing on you from the dash vents. (Like anywhere else, if you disconnect any leads, cover them [electrician's tape, shrink-tubing, etc] and secure them safely in the engine bay to avoid accidental grounding.)
tip: if your Climate Control fresh-air blower (dash switches than slide left to right) isn't working, after checking all fuses and relays, us a 12-volt battery and temporary leads to check the blower motor in the system (it's that big black lump of tubes and cables under the windshield and behind that cardboard piece). If the blower motor is out, carefully remove it and get a replacement at the salvage yard.
My fresh air blower motor burned out and I replaced mine for $50.00 and my own labor.
Good luck!!
08-02-2008, 11:35 AM
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Interrior fan issues
Thanks for the great post.
I still don't understand what controls the interior fan on an SC.Also are these the one and same fan or are there 2 fans one for the AC to blow when the AC works by the rotary switch and the another fan for the just the fresh air?
My fan behind the card panel inside the hood works fine when powered by jumpers but is this the fan that works when the AC is on?
Also if the fresh air fan is working as it appears, what atually happens behind the sliders ? are there a series of micro switches or is this a variable resistor.
No one seems to sell this part so it can't fail very often (all fuse etc intact)
I still don't understand what controls the interior fan on an SC.Also are these the one and same fan or are there 2 fans one for the AC to blow when the AC works by the rotary switch and the another fan for the just the fresh air?
My fan behind the card panel inside the hood works fine when powered by jumpers but is this the fan that works when the AC is on?
Also if the fresh air fan is working as it appears, what atually happens behind the sliders ? are there a series of micro switches or is this a variable resistor.
No one seems to sell this part so it can't fail very often (all fuse etc intact)
08-03-2008, 10:45 AM
#4
The fresh air system and the AC system are totally separate. The fresh air blower, which does not blow out the AC ducts, is at the back of the front trunk and is controlled by the heater/defroster controls. The AC blower is in the "smuggler's box" in the trunk area on the passenger side. It is controlled by the switches on the console.
The AC system only recirculates air. Getting much fresh air out of the heater/defroster system is tough.
David Nolen
'70 911T
The AC system only recirculates air. Getting much fresh air out of the heater/defroster system is tough.
David Nolen
'70 911T
