Odd blower issue with Hayward H400FDN blower or???

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ecarlseen

Member
Dec 10, 2020
9
Las Vegas, NV
I have a Hayward H400FDN and the initial problem was the 3A fuse blowing after a few seconds every time the heater started. Did the troubleshooting and replaced the control board (don't you just love that they used garbage plastic for the standoffs, wire harnesses, and MOLEX connectors?). Fuse no longer blows, but....

When I ask for heat I hear a few relay clicks and get the AO message. Blower motor windings have 4.5 ohms resistance, board is putting out ~120VAC of power. Troubleshooting process says to replace the vacuum switch and I did so because it was cheap and easy. Same problem. The vacuum switch is open / not conducting current (as it should be) in rest state. The seemingly obvious thing to do would be to replace the blower, but...

If I force a lockout / purge condition by turning off the filter pump and asking for heat, the blower motor turns on and runs beautifully. I checked the power from the board and it's still ~120VAC. I don't even have the beginning of a clue as to why the blower motor would come on for a purge state, but not for a pre-ignition state. The only thing I haven't done is dug my ammeter out of storage to see if there's a different amount of current coming in for pre-ignition vs. purge (again, the voltage is the same).

Can someone with more experience think of a reason why the motor would turn on for a purge but not for pre-ignition, given that it's the same input voltage supplied for both states? I can reproduce both conditions flawlessly all day long, and I feel like I'm taking crazy pills.
 
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I have had blower motors that are dying, still put out air, and run "beautifully". They just dont move enough air to either prove the air switch, or achieve the right air/ fuel mix to ignite the burner. See if you can see the windings of the blower motor through the motor vents. You are looking for a group that is a darker shade of copper that the other two. You might also be able to smell the burnt winding.
 
From a look at the parts list for your heater it appears that the combustion air motor is an induction start/ induction run motor. This type of motor has a very low starting torque. Not knowing the schematic for the control board, it is possible that the power to the combustion air motor for the normal call for heat and for the purge functions are supplied through different relays. If the motor is older and the bearings are marginal due to age/wear a difference in resistance in the contacts of 2 different relays may be enough to cause the motor to not start. Observe the voltage to the motor as it is attempting to start in both situations and look for a voltage drop which might be an indication of this situation.
 
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swamprat69 said:
I am reading that the motor will not start on a normal call for heat. Is that correct?
Click to expand...

Thank you for your response. Yes, that's correct. I dug my ammeter out (haven't used that thing in ages!) and it's showing [~3-4 amps EDIT: this was initially measured incorrectly] 2.0 - 2.5 amps of current when running in purge mode and the motor is running. It's showing ~0.0 - 0.1 amps when calling for heat with the motor not running. The voltage is the same either way.
 
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swamprat69 said:
From a look at the parts list for your heater it appears that the combustion air motor is an induction start/ induction run motor. This type of motor has a very low starting torque. Not knowing the schematic for the control board, it is possible that the power to the combustion air motor for the normal call for heat and for the purge functions are supplied through different relays. If the motor is older and the bearings are marginal due to age/wear a difference in resistance in the contacts of 2 different relays may be enough to cause the motor to not start. Observe the voltage to the motor as it is attempting to start in both situations and look for a voltage drop which might be an indication of this situation.
Click to expand...

Thanks for your reply. There are two set of windings on the motor, but it appears they're merged down to one set of power leads by an adapter before they plug into the control board. Voltage is the same (129VAC) either way. It's a little high because it's 247VAC in, which the transformer steps down. This is still within spec (barely) so it should not be problematic, especially for something like an AC motor.
 
Pool Clown said:
I have had blower motors that are dying, still put out air, and run "beautifully". They just dont move enough air to either prove the air switch, or achieve the right air/ fuel mix to ignite the burner. See if you can see the windings of the blower motor through the motor vents. You are looking for a group that is a darker shade of copper that the other two. You might also be able to smell the burnt winding.
Click to expand...

Thanks for your reply. The motor does indeed have two sets of windings, but they're "merged" by an adapter before plugging into the control board. The motor starts and runs happily in purge mode, but does nothing when asked for heat.
 
ecarlseen said:
Thanks for your reply. The motor does indeed have two sets of windings, but they're "merged" by an adapter before plugging into the control board. The motor starts and runs happily in purge mode, but does nothing when asked for heat.
Click to expand...
I was referring to the actual windings of the motor and not the wires that come from the motor.

Are you saying that the motor shuts off altogether after the pre-purge?
 

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The reason that I am asking these questions is that it makes no logical sense that a 2 wire / 120 - volt induction start / induction run motor will start/run in one instance and not start/ run in another instance if the supply power is identical in both instances. Also questioning if the motor is running over listed Full Load Amps when it is running, which may be an indication of both failing motor combined with a problem with poor power feed.
 
Pool Clown said:
I was referring to the actual windings of the motor and not the wires that come from the motor.

Are you saying that the motor shuts off altogether after the pre-purge?
Click to expand...

It does not start at all when heat is requested when the water is flowing (normal start). It does start and appears to run fine when a purge cycle is forced by requesting heat without the water flowing.
 
swamprat69 said:
The reason that I am asking these questions is that it makes no logical sense that a 2 wire / 120 - volt induction start / induction run motor will start/run in one instance and not start/ run in another instance if the supply power is identical in both instances.
Click to expand...

Exactly. This is why it feels like I am taking crazy pills. My internal dialog on the subject involves complex-compound profanity.

swamprat69 said:
Also questioning if the motor is running over listed Full Load Amps when it is running, which may be an indication of both failing motor combined with a problem with poor power feed.
Click to expand...

Motor label indicates amperage @ 115VAC is 2.1A. Note that my initial reading of 3-4A was incorrect because I was measuring off of the wrong wire (sorry). Measuring on the wire where it plugs into the control board indicates a startup current of 2.5A settling down to 2.0A while running.

Motor label:
IMG_9665.jpg

Ammeter reading while running:
IMG_9671.JPG
 
For the curious, here is a wider shot of the motor itself and the adapter plug its wiring goes through before it plugs into the control board:

IMG_9666.JPG

The four leads from the motor get merged into two leads here, before they plug into the control board. Yes, I'm the kind of guy who labels all of the cables.

IMG_9668.JPG
 
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