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Need relays for my Trol-A-Temp Mastertrol Mark V

tamer Member Posts: 15
Hi All,
The compressor is not coming on. I had someone looked at it and he think it's the relays.. where can I find the relays for my Trol-A-Temp Mastertrol Mark V board? Please help .. thanks


  • Ironman
    Ironman Member Posts: 6,367
    That's a very vague diagnosis. It can be easily checked with a DMM by someone competent. Did he do that, or is he just guessing?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • ratio
    ratio Member Posts: 2,765
    Post a pic of the board. Are the relays socketed? If so, post a pic showing the base, someone might recognize the brand.

    If they're soldered on to the board, consider replacement of the control. IIRC upgrading to a Honeywell TrueZONE panel isn't too hard, the existing actuators can be reused. (Search this site for "trol-a-temp".) I'd imagine that most zone panels could be used, for that matter.

  • tamer
    tamer Member Posts: 15
    @ratio both thermostats (it's 2 zones) have only 3 wires ( red, white, yellow) will that be enough for the Honeywell TrueZONE panel?
  • tamer
    tamer Member Posts: 15
    How do you check this relay ?

  • Jamie Hall
    Jamie Hall Member Posts: 15,849
    At least on my computer the pictures are too out of focus to see anything...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pecmsg
    pecmsg Member Posts: 1,986
    > @tamer said:
    > How do you check this relay ?

    With a Volt Ohm Meter
  • John Mills_5
    John Mills_5 Member Posts: 935
    About time to call the Smithsonian or get a MODERN panel with a discharge air sensor to protect against freeze ups and overheating the furnace. Also if you have a 2 stage furnace, a GOOD panel will stage the furnace (and 2 stage A/C) based on number or % of zones calling.
  • ratio
    ratio Member Posts: 2,765
    If I were going to upgrade the system, I'd go with RedLINK wireless thermostats, powered by two of the wires in the wall so you don't have to worry about batteries. Honeywell has a receiver that'll wire into the TrueZONE panel & allow the connection of up to 4 wireless thermostats. Like I mentioned earlier, search here for how to rewire the zone actuators to operate with the new panel.

    Regarding the relays, testing them isn't too hard. First, check the coil for continuity. If that's good, then check the contact resistance with the coil both energized & de-energized. If you do need to replace one (or more, I would probably do them all…), I'd start with the local Radio Shack, Frys, or whatever you have in your area. Take one in & ask them if they can match it or recognize the mfgr. If that fails, it's time to take some measurements & start googling. You'll need to know the size & spacing of the terminals. Probably any old 24 VAC relay that plugs in will work, thermostat duty is pretty light work.

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