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I needed to replace fan and limit control (White-Rodgers, model 5D51-35), because the fan switch was broken (fan would constantly run) and heat would not stay on.

I took a picture of the control, the way it was wired and labeled the wires. The control had:

  • two wires running to the limit side
  • one wire running to the lower fan side.
  • a jumper copper wire running from the upper limit side to the upper fan side.

When I took the part into the supply store the sales person told me the jumper wire was not supposed to be connected. I installed the new control without the jumper and the heat will come on, but the fan will not come on. The instructions indicate if you have a low volt or millivolt do not use jumper. How do you know if it is a low volt or millivolt system. (I'm using a 120v system.)

Do I install the jumper line because the fan will not come on. (jumper line was connected on old control)

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Is your system line-voltage (120v?) If so it is not low/millivolt. –  Steven Feb 20 '13 at 20:45
Wheres the picture, it would help to see it. –  Chimchuimann 16 hours ago
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