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I just installed a new heater motor, cables, heater core, etc. basically the whole system. I wanted to check to see if the heater fan works, so i tried it out. I only got two different speeds for the fan, even though there appears to be settings for a third speed on the switch on the dash (66 coupe). Does anyone know if its only supposed to be a 2 speed for, or is something wrong with my setup
 
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I'm not sure on yours, but some sytems start the fan on low when you move the Heat/Def lever from the off position. The fan switch then accelerates the fan to med and high speed.
 
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O.K.- where is the "off" position on your panel? If it's in the middle, you could possibly have an early 66 w/2 speed fan.
Also could be like the previous post said-on my 66 I can barely hear and feel low speed. Are you sure you got a 3 speed motor? Possibly the place you got yours, you got a 2 speed instead.
Just my .02

Was Bob Emmerich on old forum
 

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The '65 had a two speed fan motor. This is used with a two speed fan switch and the early wiring harness. This type does not have a resistor mounted in the front of the heater box and the switch connects to a harness connector.

The late '65 and '66 style uses a single speed motor and uses a resistor to control the three speed settings. A resistor is mounted in the front of the heater box. This later model switch has an umbilical that attaches to the resistor. The resistor consists of two segments of coiled nichrome wire. The nichrome wire is placed in the airflow of the heater near the heater radiator for cooling of the resistor and limited automatic fan control. The switch controls how the resistor segments are connected in series with the single speed fan motor. Each setting of the switch reduces the voltage availble to the fan motor and hence causes it to run slower for each lower setting. Placing the resistor in the airflow also results in some temperature compensation for the fan, that is, when the air is cool, the fan runs slightly faster than it does once the air warms up regardless of setting. It is possible to convert the early '65 type to the later '66 style but you have to understand how both types work and correct the differences in the harnesses. Note well that the voltage source is reversed between the two types and the harness is different. Trying to intermix parts will likely result in blown fuses. Be sure to use the right type motor and switch with whichever type you have.
 
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