Kenmore 402-89032012 - FE error code

According to the tech sheet Dan found for me the FE error code is related to "invalid power source frequency". I decided to test voltage at the terminal block from L1 to L2 and found when I started a cycle the voltage dropped from 240v to around 220v. I know my generator can run 240v dryers fine normally so I believe this test points towards resistance in the motor or blower wheel from lack of cleaning. 

After I confirmed the problem wasn't the control board my goal was to figure out how to diagnose the problem before tearing the machine apart trying to stimulate a real service call. I'll clean it out and report back on if that fixes the problem. 

Yeah, it definitely seems like a tough one you've got there. Only other thing that I could think of at the moment would be checking for any obscure wiring issues such as loose connections and what have you. And there are times where a load can test good for resistance, but can fail under load.

The process you used for voltage checks is spot on for what I was going to initially recommend -- checking to see if there is any voltage being dropped to the unit.

Generally speaking, 220 VAC will still work, we'll just have slightly reduced heat output. But the thing to zero in on is which leg of voltage is dropping down. L1 and Neutral are generally used for the motor circuit and the board, and L2 is typically just for the heating circuit. So, if you're dropping the 120 to the board and, say, it goes down to 100 VAC, then that might be a problem.

The other thing I would recommend is that you trace out the voltage. I have seen good voltage at the terminal block, then some crazy readings at the board itself, pointing toward a loose connection or a wiring issue.

I've been a bit busy this week as my work schedule has changed for training purposes, so I am lacking the hour or two I generally have in the mornings. When I get a chance, I will review the schematic for this unit and will see if there is anything else I can think of.

Otherwise, you're on the right path -- making checks to see what is testing good, and where there might be some issues. That's the key to appliance repair, rather than just replacing parts until the issue is resolved. 

The other thing to keep in mind is that when you're dealing with control board logic, manufacturers are often not providing us with the information we need to fully understand what factors come into play when you're seeing an error code. They consider it "proprietary," or just don't take the time to detail it in the technical documentation.

Yeah, that's the type of information I was looking for. A way to prove it's the motor for sure before tearing it apart. Testing from the board on this specific dryer is kind of precarious when it's running due to where the board is mounted but I'm sure I could have done it. I attached a picture of the schematic, I'm not totally sure but I think I would test from connector 5 pin 1 BRN wire to connector 6 pin 5 RED wire to isolate the motor circuit and check for voltage drop upon startup? 

The motor wasn't overly dirty but I did find that the motor in the bad unit has excess axial play and what looks like an exposed bearing seal, so I'm almost positive it's the motor. I have one motor out and one with a stuck fan that I'm trying to figure out how to get off and then I can swap, reassmble and see if that fixes it.

Looks like I was wrong. Got the new motor in and it does the same thing. I think that points to the problem being caused by the heating circuit. I verified the element isn't broken and isn't grounded to the case.

I know the unit did the same thing plugged into the 240v outlet in my inlaws house that now runs a dryer just fine, I was lucky enough to have the same board on hand and swapping them didn't fix it. That leads me to believe what the board is seeing is correct. However, the service manual says FE means "invalid power source frequency" and to check for: "not using valid power source frequency" and "invalid power frequency sense circuit". 

I think that first sentence means using a power source that is not 60hz. I don't believe I have reason to suspect that is now, or ever was the problem.

Which leaves me with the possiblity of an invalid power frequency sense circuit. The little information I was able to find on what that is makes it sound like that circuit is fully integrated into the circuit board and it's proper operation isn't verifiable, or accessible for testing. 

After all that I'm mostly lost but the one question I have is, is there anything that can physically go wrong with a component, or the wiring that would make the frequency sense circuit detect a problem? 

Should I just do my best to trace voltage on the L2 circuit from the terminal block to the appropriate board connection and see if I find anything strange? 

As to the motor circuit, I have added a screenshot of the test points that I would use to check it from the board. I will see about making a video on finding test points when I get a chance.

The other the other thought that I would have is this: Disconnect loads from the board, run the unit and see if there is a particular load that might be causing the issue. 

Every now and again when it comes to repairing appliances, you are going to come across a situation that absolutely baffles you, and this one seems to be one of them. You have effectively ruled in and out a lot of things based on what you've done so far.