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Refrigerator Evaporator Fan Motor Hack

Permalink 01/01/25 12:26, by OGRE / (Jeff), Categories: Welcome, Background, In real life, On the web, History

I woke up one morning, and began cooking breakfast so we could all go out for the day and get food for our Thanksgiving dinner. When I opened the freezer, I noticed that all of the ice was stuck together. The refrigerator compressor was running, but the evaporator fan wasn't running. It's an older GE fridge that was in the house when we moved in in 2011.

I have replaced the evaporator fan motor once before on this refrigerator. I found the motor in my Amazon order history, and got another one on the way. In the meantime, I need my fridge to keep working. So I decided to rig it with another fan motor for the time being.

The original fan has some weird voltage listed 9.75 Volts DC 3.25 Watts. They're variable speed motors, kind of like the 4-wire fan motors that they use for a CPU cooling fans.

I don't have anything like that laying around, but I do have a Nidec fan that came from the top of a computer server rack! It's 12V DC 1.4 Amps, it will move some serious air, also it's around the same diameter as the stock fan.

I pulled the evaporator fan housing out of the fridge, lined up the Nidec fan in the center of the air outlet, marked the housing and drilled 4 small holes to mount the Nidec fan. I used some rubber grommets between the fan housing and the fan, in the hopes that it would keep it from being too loud.

Here it is installed.

Now all that was left was some way to power the fan, and get it to run when the compressor was running. I figured that the original control circuit was still functional, so I wired the fan power to a 12V DC relay, then ran power from my power supply through that. I used some of those little magnets with hooks on them to route the wire and hang the relay.

But it didn't work. Apparently these variable speed fans have a tach signal that comes back to the fan's speed controller, again like with a CPU fan. If the controller doesn't get a tach signal back, it kills power to the fan. So my new fan started and ran for about 30 seconds, and would then shut right back off again.

However, I'm not one to give up so easily. I went to the next step and decided, I'll just use a 120V AC relay, and parallel the relay coil to the power for the compressor. Problem solved. In this picture you can also see the power supply I'm using. It's way overrated for the load, but that's OK because with switching power supplies they only use what you draw (with the exception of control circuitry) which is negligible.

To connect to the power wires for the compressor, I used those T-Tap connectors. They make some that have a female spade terminal built in. These are great, because you can use them without having to hack up the appliance's original wiring harness, and when you're finished you can just unplug the spade terminals and you're done.

I just used 22 gauge 6 conductor wire to power the fan, because it is small enough to allow for the door to still seal well. I just opened the jacket where it exited the fridge, so it was flat.

With everything in place, it was time to test it. Did it work? Oh yeah, it worked and the fan moved about the same amount of air as the factory fan!

The only downside was the noise. That Nidec fan is LOUD. Whenever I was on the phone with and I was in the kitchen, people would say, "Where are you? It sounds like you're in a server room." I had to let them know, it's just my refrigerator since I've rigged it.

Of course, I didn't want to leave it that way (insanely loud) so when the new fan arrived, I went ahead and put that one in.

Everything was looking good. But when I went to test it the fan would never start. Long story short, the main control board for the fridge was messed up. I looked online and found some information on the board. I don't have a schematic for the fridge, so I was looking for a video that might show a picture of one -- and I finally found one!

It might be hard to see, but there are four wires that go to the evaporator fan motor.

13V DC (Red)
Common/Negative (White)
Speed Control (Yellow)
Tach Signal (Blue)

The yellow wire is Yellow with a Black sripe at the control board, so I could test for voltage there (it changes from yellow/black to yellow at the fan connector). There was 13.2 volts there at the control board, but for some reason as soon as you put a load on it, it would drop to near zero. The power supply built into the control board was bad.

Now worries, I found that I could hotwire the OE fan. Worst case I would have to put the Nidec fan back in and rock that until I saved up for a new fridge.

To test the OE motor, I used a drill battery that is 12V DC. If I powered it with the red and white wires, then also put 12V DC on the yellow wire, the fan would take off at full speed. So that's what I did. I just ran two wires to the fan, negative and positive, and jumped the red and the yellow together. So now the OE fan motor will work, powered externally, with a relay to turn the fan on and off.

To make it look nice, I hung everything behind the fridge using those little magnet hooks. For now that's how I'm going to leave it, because everything else on the fridge works correctly. The temps read right, the automated airflow damper for the refrigerator side works, and the ice maker and water dispenser are all working fine.

Good times.

Buy me a Ko-Fi 😉👉

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