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CAC/BDP Three Wire Pilot Troubleshhoting

rucomfyrucomfy Posts: 43Member
I am looking for learning resources to learn
and understand how a 3-wire thermal pilot works.

How does one go about troubleshooting i.e. pick coil, hold coil, main coil etc.

Thanks for your help.

Comments

  • Empire_2Empire_2 Posts: 2,343Member
    3 wire pilot burnrer:

    This pilot safety switch is very common in Bryant/Carrier earlier model equipment. It's primary function (Safety control) is to switch over to main valve once a satisfactory pilot is established. As the attached diagram depicts, the NC set of contacts (on a cold start) allow voltage thru to the pic on the 5 wire GV to initiate pilot solenoid and the hold point is to keep the solenoid energised upon switching on the pilot control to main valve thru the (NO) contacts which close upon heating of the warp switch. Upon energising Main valve the spark igniter is also De-energised stopping the spark generator. At any time, either thru poor pilot flame or weak pilot switch you can experience a back and fourth switching action that will give you burner on, burner off situation.

    Another scenario: If you get pilot flame and then as switching to main valve the burners quickly light, then out and back and fourth like that (sounds like clicking back and fourth and back again), you actually have a bad hold coil on the GV. Many times this is usually blamed on the pilot switch, but in fact is a valve problem. I like to replace the Pilot burner roughly about every 5 years or so depending on it's response time to switch. I like to see it switch over in about a minute or so.

    To experiment, hook your meter up to the "Yellow and White" wire and you can actually watch the control switch and get a feel of how long it takes the switch to occur.... Kinds of neat for the novice willing to learn.

    I Hope this helped you......

    Mike T.
  • rucomfyrucomfy Posts: 43Member
    Mike T.

    Thank you for taking your time to help me. I am going to start looking in my archives for Carrier/Bryant literature and hvacpartners resources. Like Joe McCarry or was it "my" Uncle Wayne said.. "It's still out there.." Best regards and thanks again.
  • carol_3carol_3 Posts: 397Member


    Wow, Mike, I had no idea . . .
  • Allan I will look thru

    my Carrier/Bryant info and I believe I have a book that explains that entire system. Mike T did an excellent job however explaining it.
  • kozkoz Posts: 1Member
    3 wire Bryant issue

    I changed the 3 wire pilot but still having the same issue. The pilot lights up then when its warmed up it clicks rapidly and just keeps lighting the pilot....nothing else happens just pilot on and off repeatedly. Its a 395baw
  • > @koz said:
    > 3 wire Bryant issue
    >
    > I changed the 3 wire pilot but still having the same issue. The pilot lights up then when its warmed up it clicks rapidly and just keeps lighting the pilot....nothing else happens just pilot on and off repeatedly. Its a 395baw


    Hey, did you find put what the problem was?? I'm having the same issue in a Bryant 376A and I'm about to replace the 3 wire pilot, but after seeing your comment I'm kind of unsure now.
  • Fritzy1342Fritzy1342 Posts: 1Member
    I have BDP376 that I’m having trouble with. When turned on the igniter sparks and the pilot will light for a short time (3-5 seconds) before going out. I’ve replaced the warp switch/pilot but it’s still the same. I hear a rapid clicking from the gas valve ... wondering if I have a solenoid issue in the gas valve? Any input greatly appreciated thanks!
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