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HVAC controller issue

I find it hard to believe your control was defective out of the box. I would be inclined to believe that something in the ignition sequence is causing an amperage spike on the contol voltage side downstream of the control. If the amperage on the secondary side(24 volt) side of the transformer sees amperages exceeding 1.67 amps the integrity of the contol and coils are compromised. Be sure to install a 3 amp or smaller fast blow fuse in the secondary wiring if there isn't one already there. Good luck.

Comments

  • Tymme
    Tymme Member Posts: 4
    HVAC controller issue

    Hi,

    Having trouble diagnosing a GFA furnace issue. I have an Amana Aircommand 90 (90K btu) vintage 1987.

    The unit won't fire up. Ignitor doesn't energize. The controller (White-Rodgers 50E47-170) gives an internal failure mode (solid red l.e.d.) I replaced the controller with the superceding model 50E47-843 and have the identical failure mode with this new controler also (solid red light).

    My question is, could this new unit also be defective or could there be some other problem that would cause the controller to deliver an internal failure response?

    Things I have checked:
    Voltage to controller (L1 terminal)=122.3v
    Voltage across TH and TR terminals = 26.7v (a bit high but a problem?)
    Resistance across ignitor is within factory spec (68 ohms) and is new.
    Flame probe is clean and properly grounded
    Transformer should be working based on the voltage across the TH-TR terminals, correct?
    Combustion relay appears to function properly and looks perfect (clear case)
    Combustion blower comes on and vents properly
    Combustion blower diaphram switch seems to work properly -can activate controller by sucking on tube thus closing switch.

    So, everything seems to point to the controller but I am *really* hesitant to buy another new one ($$$!!!) just to have it go bad if there is something I'm overlooking?

    Help?
    THANK YOU!!!
    =Tymme
  • Tymme
    Tymme Member Posts: 4
    HVAC controller issue

    Hi,

    Having trouble diagnosing a GFA furnace issue. I have an Amana Aircommand 90 (90K btu) vintage 1987.

    The unit won't fire up. Ignitor doesn't energize. The controller (White-Rodgers 50E47-170) gives an internal failure mode (solid red l.e.d.) I replaced the controller with the superceding model 50E47-843 and have the identical failure mode with this new controler also (solid red light).

    My question is, could this new unit also be defective or could there be some other problem that would cause the controller to deliver an internal failure response?

    Things I have checked:
    Voltage to controller (L1 terminal)=122.3v
    Voltage across TH and TR terminals = 26.7v (a bit high but a problem?).
    Resistance across ignitor is within factory spec (68 ohms) and is new.
    Flame probe is clean and properly grounded.
    Transformer should be working based on the voltage across the TH-TR terminals, correct?
    Combustion relay appears to function properly and looks perfect (clear case).
    Combustion blower comes on and vents properly.
    Combustion blower diaphram switch seems to work properly -can activate controller by sucking on tube thus closing switch.

    So, everything seems to point to the controller but I am *really* hesitant to buy another new one ($$$!!!) just to have it go bad if there is something I'm overlooking?

    Help?
    THANK YOU!!!
    =Tymme
  • David_25
    David_25 Member Posts: 3
    Is an AQ 675 for injection pump or mixing valve?

    I have an AQ 675 reset control with a 4 way mixing valve. I have been told I should use a AQ 775 control for this setup. For the life of me everything I read says the AQ 775 is for injection pump. Confused in Massachusetts's.

    A second issue is my AQ 475 control not resetting the boiler temp. I am starting to think my collection of controls was a poor choice. Is there a better way to more accurately control a boiler and maximize efficiency? I am running constant circulation now also.

    Thanks

    David
  • Does the new 50E47-843

    have the "D" program key inserted (violet)?

    Did you remove the jumper from "FP" and throw it away?

    After prepurge do you have 120 volts at HS1? The igniter should be wired thru an adapter? If it is then the red wire from adapter to L1 should have 120 volts, then you should have 120 volts out of HS1 Blue wire back to the adapter then to the igniter. If you have 120 volts and the igniter does not glow the igniter is faulty.

    The only other thing that will give you a "RED" solid on is a flame sensor shorted to ground. Put meter on the Ohms scale with power removed go from the sensor rod to ground if you have continuity it is shorted to grund somehow. Replace the sensor.

    With the "D" program key you should have 2 retries with 30 second prepurge and 45 second igniter warm up time.

    The 50E47-843 is a White Rodgers universal replacement control for the one you replaced so it should work.

    Do you have a programmable "power stealing" thermostat on this system? If so the power stealing feature can cause "electronic interference" with some controls.
  • Tymme
    Tymme Member Posts: 4


    The "D" chip is inserted

    The jumper is disconnected

    The ignitor is wired thru an adaptor and I get 120v (122.3v measured) from the L1 termimal (red wire)

    I do not get 120v from the HSI terminal because the controler goes into failure mode before prepurge is done.
    Failure mode is achieved in about 3 seconds. The light sequence during startup is: about 2sec with solid yellow light, then a *very* brief flash of green light followed immediately by solid red light

    Again, time to failure is about 3 sec.

    Checked FP. No continuity between rod and ground

    I do not have the thermostat you mention (I don't think) I have an old Sears Kenmore Thrift stat -the old mercury type switch. Looks pretty bombproof.


    Thanks!
    Cordially,
    =Tymme
  • I would take the

    new module back and tell them it is defective.

    Try using a Honeywell S-8910U Universal replacement. It comes with an adapter for connection to White Rodgers system.

    Otherwise have a heating technician check it out.
  • Tymme
    Tymme Member Posts: 4


    Thanks so much for your help and suggestions!

    I have ordered a Honeywell board as you suggested and will give this a try.

    Just didn't want to throw good money after bad and make sure I wasn't overlooking something due to my lack of knowledge and understanding.

    Thanks again!!
    Cordially,
    Tymme L.
  • carol_3
    carol_3 Member Posts: 397


    The AQ675 is for mixing valves. The AQ775 is for injection pumps.
This discussion has been closed.