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Honeywell fan limit

Dick J
Dick J Member Posts: 2
The older low voltage fan limit I am replacing (with honeywell 4064B) has two more wires than the new one, they are coming of either end of primary control. I know I have to break the strip out of the new one for low voltage, but do not know what to do with the other two. Any help would be greatly appreciated


  • Gene_3
    Gene_3 Member Posts: 289
    if you had

    the wiring diagram from the unit it would help, the control is a fan/limit a fan control and high limit

    it is possible that 2 wires are for the fan and 2 are for the limit, your problem is which 2, the Honeywell control is clearly marked what side is what and when working with hi and low volts the jumper must be broken, you got that far, if you had nade note of where they were before disassembly that might help or trace them out follow them.

    If your not sure it may pay to have a pro come out because if your wrong and turn it on you will see smoke and then $$$$
  • Dick J
    Dick J Member Posts: 2

    Old unit has 6 wires, new unit only has 4 terminals
  • Tom M.
    Tom M. Member Posts: 237
    Sounds like a 4064 W

    Are the two extra wires plugged into the middle of the control?

    The 4064W has a heat operated switch that will start the fan a number of seconds after the burner starts. This will protect the furnace from overheating before the probe gets hot enough to start the fan. It is useful for horizontal units where there is little gravity flow from the heat exchanger to the fan/limit. The two wires in the middle are the 24V supply to the heater. If these are wired to the T and F terminals on the burner control, be sure to use an amp meter to set the heat anticipator on the tstat because the current for the heater must be added to the .2A for the burner control.

    I noticed you said the wires are coming from either end of the primary control. Are you replacing it because the fan runs all the time? I think it should be wired from the bottom F terminal and the bottom T terminal so that 24V is only applied when the tstat is calling.

    Hope this helps.

    Tom M.
  • Gene_3
    Gene_3 Member Posts: 289
    there comes a time

    when you have to hire a pro, I am assuming you are a DYI, I don't mind giving advice to techs or advice to homeowners wondering if they are getting the straight skinny, but it sounds like you are over you head, this is why we get the big bucks, I too do as much as I can myself at home but I have a cut off point.

    The first thing you always do is make a wiring diagram before unwiring anything and trace them out so you know what went where and why, this makes it easier to transfer from one manufacturers control to another, it sounds like you are trying to replace a control that won't do what the original did.

    You may be able to use a Camstat but this control has confused more than one tech as to which wire goes where, when you ask them why they are not clearly marked their reply is "if you can't figure which is which with a meter you should not be working on this"

This discussion has been closed.