Penguin A/C Fan Motor Replacement

We had a significant rattle from the fan motor in our rear air conditioning unit.  While the motor was turning freely the shaft was able to slide from end to end horizontally through the motor more than it should and that would generate a wobble when spinning.  The vibration was so bad we could feel it in our body, the bathroom mirrors and the sliding glass closet doors were rattling worse than driving the rig.  It was clearly something that would need to be addressed before more damage ultimately would occur.

This project took me about 1 hour and only two trips up and down from the roof.  This is not intended to be an all-encompassing how-to guide.  This is a potentially dangerous project given the electricity that may be retained in parts of the unit, even when there is no source of power connected.  I am providing this as documentation of how I did this and am noting to my future self what to remember.  I take no responsibility for your project and the results of it.

Specifications

Both of our air conditioners are Dometic Penguin low-profile heat pump air conditioners, model #630515.331D, part #991761221.

The specific motor used in the unit is an A.O. Smith, model #F42E85A61, (a/k/a #3308039.019) which amazingly is still readily available now more than a decade after the original manufacturing.  This motor appears to be available on Amazon for over $200 now.  I acquired it from an eBay seller which was very quick and was less than $100 ($69 + $18 shipping) for the part. The eBay version did not come with a new foam ring on the shaft for filling in the airbox.

The only other minor part needed was a way to terminate the yellow wire (medium speed) to prevent any grounding of the wire.

The motor being replaced is an A.O. Smith F42E85A61 1650 RPM 3-speed motor. Even though only 2 speeds are used the motor is capable of 3 speeds. The new motor is an identical part number and specifications. Unfortunately the same amperage as 12 years ago, no modernization of this thing!

Tools

The tools needed for this project are pretty straightforward.  The wiring is mostly just plug and play (with pre-determined ends) with the exception of the yellow wire that needs to be insulated.  The motor is mounted with three different bolts and nuts.  The electrical box and fan shroud have some mounting screws.  The one thing I did not anticipate was having the need for a proper hammer.

Tools used for the project: 8mm, 9mm, and 10mm ratchet wrenches, T3 and T4 T-handle hex, 15mm open-end wrench, multi-driver, a “hammer” and a wire tool for needle nosing stripping and crimping. Finally a “butt” connector for capping the yellow cable.

 

Wiring

An air conditioning unit consists mostly of two major components, the compressor for magically cooling (or heating when in heat pump mode) and the fan motor for moving air through the coils.  There are two “squirrel cages” mounted to the fan motor on a shaft that goes through the motor.  The compressor, associated components, and the fan are all wired into the electrical box. In the electrical box is a circuit board and supporting electronic components for managing the voltages.  One of those is a huge capacitor that can retain electricity for days, so be careful!

Overview shot of the electrical compartment inside the overall shroud. You will need to remove 2 bolts from the cover. Danger lurks in here, electricity can remain in the capacitors and other electronics so beware even though you have the source power removed!

Procedure

The basic steps include removing the power by turning off associated circuit breakers to both A/C units.  Removed the outer shroud, each of the fan box components (the exterior fan box has two screws holding it in place), and the cover from the electrical box.  I cut the wires from the old motor, leaving the wires in place to remember where to put the new wires.  Removed the motor (3 bolts and nuts) from the chassis.  Marked the distance from the end of the shaft for each squirrel cage and removed the cages.  Then put the cages back on the new motor and reversed the process to re-assemble.  The wiring required the removal of the grommet so that the new wiring could be put into place.

The motor is fixed to the overall cabinet in three places. There are two rubber isolated bolts on the brackets of the motor. Then on the long shaft side of the motor, there is a stand-off the supports the motor with a smaller post built into the motor.

 

Before you remove the cages make sure to measure or mark the offset you will need when putting them on the new motor! Both of the squirrel cages can be removed with a T-handle hex driver. You will need 4 mm for the larger and 3 mm for the smaller cage. One of the cages required some convincing to remove, so I used an open-end box wrench to seat over the shaft and then hammer it loose. The cages went back on the new motor with no resistance at all.

 

The wires are all fed through a grommet from the mechanical area to the inside of the electrical compartment. You will not be able to feed the spade plugs through because of how many wires are already in the grommet. You can squeeze the grommet and push it back out, open it up, lay in your cables, and pop the grommet back into place.

 

New motor in, foam insulator on the inside (right) compartment, wireless on top of the shaft, and ready to lace on the outside compartment (left) up to the compressor (top) compartment.

 

 

The yellow wire is for the “medium” speed on the motor. In this configuration you will only have a high and low speed, the control system does not have a medium speed. The original wire is capped, I used an end to end splice connector to cap the wire in the electrical compartment.

 

Oops

There is always an oops or two, and some blood, associated with every project.  Besides slitting my wrist on the sharp aluminum fins of the exterior coil you have to work over, I wired the unit wrong and forgot to lace up the compressor motor wires.

THERE ARE TWO BLACK WIRES IN THIS PROJECT, MAKE SURE TO KEEP TRACK OF WHICH GOES TO WHERE! 

The next morning I had to go back up on the roof to double-check that I had laced up the compressor wires and I had not done that.  Fortunately no damage from either mistake.

New motor in, foam insulator on the inside (right) compartment, wireless on top of the shaft, and ready to lace on the outside compartment (left) up to the compressor (top) compartment.

 

There are two black wires in this project!! The black/white bundle is the 110 VAC that drives the motor. The black/red/yellow wire is the speed control. The black/red combination goes to the circuit board. The yellow is capped. The black/white combination goes to the capacitor top. I had forgotten about this difference and wired it wrong at first. When applying power the motor just hummed. Fortunately, no damage appears to have happened after I re-connected the black wires to their proper terminals. This could have been a very costly mistake.
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