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Want contol of heater fan speed on '78 Seville

Started by David Randall, January 04, 2010, 05:28:27 PM

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David Randall

Hello gain All,

How can I gain control of the heater fan speed on my '78 Seville? I live on Vancouver Island BC, and it's rainy so much of the time that the defrost has to be on, but it's always full blast which is annoying. My car does not have cruise-control (which annoys me), so I have room for a switch beside the light switch.

Anyone? Bueller? Anyone?

Thanks,


David

TJ Hopland

Let me see if I understand the question.

You want to be able to control the speed of the fan when its on defrost?   

Do you still want it to run 'normal' on all the other settings?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

bcroe

I suppose you want to use the climate control; you just want to slow down the blower on DEFROST which is normally full speed?  You could wire a resistor in series with the motor, then use a dash switch to short out the resistor for full speed.  The type of resistor used in heater motor circuits could do it, pick the tap giving the speed you like.  But these must be mounted in the air stream to dissipate the heat.  Bruce Roe CLC # 14630

Tim Groves

Does the fan blow on the Bi-Level setting?  That setting allows some heat to go to the windshield, and some to the floor.  And that fan speed is determined by the in car temperature.  The automatic control is determining the fan speed, but the Bi-Level setting splits the air flow to both the windshield and the floor.  Tim

"Cadillac Kid" Greg Surfas 15364

David,
Just "rainy" doesn't require the use of "defrost" in the AC system.  With a properly operating system, the air is de-humidified and then reheated to the provide cabin comfort conditions.
Typically, the Defrost operation is used where there is frost on the outside of the window and you need to heat the window to "defrost" it.
The system has been designed to provide full fan operation when in the defrost mode since it takes the extra effort of the fan running at full speed to get the heated air through the restrictive "ducts" to the outlets below the lower edge of your windshield (or windscreen fou you guys down under and in the UK).
Your need for fan control during defrost brings a question to mind.  Is the rest of the AC System operating correctly, providing heating and cooling in response to the temperature control settings?
Greg
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-