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Jay T
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As some of you already know, the two speed fan switch is dependent on a resister attached to the driver side of the blower housing.  The high speed fan setting is accomplished by allowing a full 12 volts to reach ground via the fan switch and the low speed is a result of a reduced voltage due to the resistor.

My low speed doesn't work.  I checked the wires and determined the problem is the resistor.  After removing it, I found one of the connections to be a little loose.  I was able to make a solid connection with a tap from a hammer on a screwdriver on the rivet holding the connector.  Next I checked the resistence and came up with around 3.3 on a scale of 200 ohms on my digital volt-ohm meter. This included the low speed wire from the resistor to the switch, green/yellow.

Question: does anyone know what the resistance should be?

Note: in my car ('74 JH5), the high speed (or full speed) wire color is green/slate and the low speed wire color is green/yellow.  This is the reverse of what is specified in the very nice wiring diagram I downloaded from this site.  The diagram has been of great help to me.

Mark Rosenbaum
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I have a brand new heater resistor ordered from Delta some years ago and installed on my spare heater box.  I was quite surprised to discover that it now has the same problem with loose connector rivets that you mention, as it did not have that problem when purchased.  (Sort of annoying for what was IIRC a US$30 part.)

I've measured its resistance with two different multimeters.  One, a Fluke 76, reads 1.9 ohms.  The other, a Fluke 77, reads 3.3 ohms.  Due to the loose rivets, these measurements were made on the foil side of the resistor, not on the connectors.



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