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GE PFE29PSDASS Low Ice production, icebox fan moving air backwards!

Ice maker in the left french door at top. I noticed a week of very low ice production. I have full service manual and ability to do all diagnostic tests. The ice box fan is blowing but it is coming out of the RETURN port on the upper inside of the left fridge (lower slot) rather than the SUPPLY port (upper) I can blow air through either port and it comes strongly through the other so no obstruction. All other fridge fans working, keeping temperature well.

I swapped the icebox fan with a new one (doubt it would change and it didn't) My repair manual says the door control board controls the door icebox so I swapped the control panel with another identical fridge. Before swapping I confirmed that in the other fridge the air was coming out supply and slight suction present on the return holding a piece of paper up over it.

swapping the control board changed NOTHING on my fridge. Somewhere a control board must be sending a negative 12v signal instead of a positive 12v signal to make the fan run in reverse?

Do I swap out the main board next?

The only trouble code I have is Fault 10, FZ icemaker Mold Body Thermistor (MB) Invalid. I don't have a Freezer icebox so that code is confusing. But there is a thermistor in my icebox which is replaceable only by cutting and splicing wires according to the manual.

This sounds crazy but if the computer doesn't get a reading from the thermistor int he icebox could it think it is frozen or out of range and could the computer reverse the flow to try to let it 'thaw out' or is that a whacko idea?

I'm stumped!!

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I ran the diagnostic test to produce the resistance reading of the ice mold thermistor and the icebox thermistor. They are showing similar resistance values. I took the ice box one out of its holder by the wiring harness and warmed it in my fingers and I can see the resistance go up accordingly. Not sure where to get to the mold body thermistor and if that is even for my model since it says FZ in front of it.

The chart shows if the freezer is set at zero (mine is) the icebox in the door should have a temp of around 15 degrees.

The resistance value I'm getting with both thermistors in that area according to the chart in the service manual correlates with a temp of about 35-39 degrees which tells me the cold 'supply' is not pouring in the top of the icebox compartment. The manual says the ice box compartment has to be below 32deg for 50 min before it will allow it to make ice.

So I think I'm back to how to get the air to come out the top Supply port again!! Thanks!

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Hi @jaacjlaem

Just for elimination purposes, have you measured the actual temp in the ice box and not just relied on the thermistor reading?

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no, but certainly can do. I think I have a small thermometer I can leave in there. The system ran this morning and afternoon and made like 12 pieces of ice. They stayed frozen in there. However the thermistor that is right behind the plastic cover that covers the wiring is suggesting a higher temp than the one under the ice mold system which makes sense because when the ice collection container is in the door it is blocking both the air inlet hole on top and the exit hole on the bottom with just a 3/8" or so gap all around. If the air is now pumping into the bottom hole and against the side of the collection box I don't see how it will get up and in the top of the area where the cubes are and if that thermistor doesn't read below 32 it isn't going to agree to make ice (at least that is what I gathered by reading the service literature.) Thanks for the help!

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@jaacjlaem

If the area is enclosed the temp should eventually equalize (or nearly so) between the top and bottom areas.

If not there's a leak somewhere.

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The seal around that area looks good but I can check. My instinct is that this won't be resolved till I can get the icebox fan down in the freezer section to be commanded to spin the opposite way and send the air through the supply tube and drop back down through the return tube. It baffles me what could be causing the fan blades to spin at the proper RPM but in the opposite direction (and 2 fans I tried are both doing this)

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@jaacjlaem

Looks like the IM mold body thermistor might be in the ice maker.

Maybe it's a wiring problem between the ice maker and the mainboard.

On p.123 of the manual you linked (thanks for that), you'll see that there's an IM thermistor signal wire on mainboard J10 connector pin 8.

You may have to check if there's continuity on the wires between the J10 cable harness plug and where they connect in the icemaker, especially the IM thermistor signal wire, the +5V supply to the icemaker wire and the sensor enable lead as shown.

Note: Your refrigerator model number isn't shown listed among the models in the manual you linked so hopefully it is relevant to your model as well

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Hi @jaacjlaem

If the wiring is as per the diagram on p.123 of the manual, disconnect the power to the refrigerator and then unplug the mainboard J10 harness cable from the board and then use an Ohmmeter to measure each wire on pins 7-12 for continuity from the cable plug (not the board) to the refrigerator's ice maker harness cable plug connection

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OK, I can follow your instructions. However under the icemaker and behind the cover there are 2 different connectors, one with two rows of 3 pins and the other is a flat single row connector. I guess I can test all of them to try to figure out the continuity. You mentino a signal wire, a +5v wire and a 'sensor enable' wire, are they labelled or color coded some how?

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@jaacjlaem

The manual shows a 5 wire connection and a 3 wire connection on each side of the ice maker but whether they are in different plugs in this configuration or not I don't know

The manual also shows the wire colours but I don't know if they are the same in your model. You can only check the colours on the pins at the mainboard and see if they're the same at the ice maker end and then test if they are the same wires.

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I had one other brainstorm. During diagnostic mode the fan spins in the correct direction. Out of diagnostic mode it reverses. The wall supplies 100V alternating current. Somewhere in the circuitry is either a A/C to DC inverter or at least a transformer to get the 110v down to +5v to send down the wire to the ice maker. Could it be that transformer is to blame and somewhere in the transfer I'm getting a negative 5v and the fan is reversing flow? Would the circuit page schematic tell us how power is transformed and would we have an option to swap out a power regulator/transformer?

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@jaacjlaem

There's no diagram of the main board itself and that's where the AC would be stepped down and rectified to DC.

If you're keen you could trace where the AC input on J1/6 on the Mainboard goes to on the board and then see what components it connects to first (besides a possible fuse and mov suppressor if they're there that is)

If you reverse the +13.2V DC output (ice box fan uses 13.2V DC) of the rectifier circuits (there's also a +5V DC supply as well so you need to find the right one) then a lot of other functions that rely on the +13.2V supply wouldn't work and may possibly be damaged as well.

The manual you linked shows that the ice box fan for all models is connected to Mainboard J8/2, /4, /6 & /8 (power +ve and -ve an rpm lead and a temp lead - see p.123 and is not connected to the door board control board - see Profile door on p.125

Not sure if you've swapped the main control board or only the door control board

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