Heat resistor

[DisneysPatB]

I would like to revisit this topic. Reading some of the old posts on heat resistors, I saw that older vehicle within the range (1970 F250) would work, so I picked up a Scott Drake 65 - 69 3 speed resistor with 4 tabs on it. Will this work, if so how do I wire it?

[basketcase0302]

DisneysPatB
I would like to revisit this topic. Reading some of the old posts on heat resistors, I saw that older vehicle within the range (1970 F250) would work, so I picked up a Scott Drake 65 - 69 3 speed resistor with 4 tabs on it. Will this work, if so how do I wire it?

Pat I think the only way we could tell how to wire it would be to have a good used resister from the bump era on a bench and you new four wire one beside it.

We'd measure the ohm resistance from the common wire through each winding on the bump era resistor / then measure the ohm resistance on the new 4 wire resistor / then use the 3 winding terminals that ohm measurements match the bump era the closest.

You might be able to cheat and do a bench test on it also.
Try to visually look at how many windings and how thick each winding is then compare the two that way.

[zgerbic]

The mustang resistor is essentially the same as the truck resistor, just layed out differently to fit the different housings. Both have two resistors in series. High speed bypasses the resistors. Medium speed powers the connection between the two resistors. Low speed provides power through both resistors.

The mustang resistor has four terminals, three to the three speed selections in the switch, same as in the truck. Fourth is a connection to the fan motor, which is a jumper on the resistor to the high speed connection.

The truck resistor has three terminals, three to the three speed selections in the switch. One of the connections on the plug has two wires. One wire is the high speed from the heater switch and the other is to the fan motor.

While the truck resistor/plug shares one connection with two wires, the mustang resistor separates these two wires onto two connections on the resistor housing. You can see this on the back of the mustang connector. Note that two connections share a metal jumper.

The connection on the mustang resistor that shares a connection with the fan connection is the high speed wire. The connection oriented differently (through a coiled resistor) is the medium speed connection. The connector parallel to the high speed/fan connectors (through the other coiled resistor) is the low speed connection.

If you look at a truck and a car wiring diagram for 1968, you will see the wiring numbers and can probably find the colors as well.

Hopefully this helps.