Help-0, thermistor isn't shorted. XMT 304

[ArcTan]

I'm getting an occasional help-0 error (and no "thunk") when I switch this thing on. The service book says it's the thermistor RT2. I've checked the thermistor for proper resistance, and swapped it for a different one and still occasionally have the same issue. Usually I can turn if off and back on once or twice and then it'll turn on and work normally until the next time I try to use it. Any ideas or further troubleshooting I should do for the thermistor?

[ArcTan]

Looking again today I noticed some of the lugs are partially pulled out of the board.

L1-1 and L1-2. Gonna fix these and see if it makes a difference

[ArcTan]

Fixed those lugs, still gave help 0 message at first power on, but then was fine the next couple times. Haven't had another chance to try it since

[Sberry]

Once it fires up,,, leave it on,, ha

[ArcTan]

That's an idea, could leave the leads connected to discourage unwanted visitors to my shop too

[duaneb55]

What's the discoloration at the lead terminal circled in red?

[ArcTan]

Dust and grime

[duaneb55]

OK. I thought it looked like a bad crimp that has been arcing.

[ArcTan]

New clue: I noticed that whenever it decides to give the Help-0 code, it doesn't make the normal "thunk" noise. So I took the cover off and wiggled the connectors that go to the contactors. Tried again and one contactor "thunked" but the other didn't, and still had Help-0. So I took off all the connectors on the top circuit board and made sure they had a tight electrical connection. Tried it a few times since then and 100% working so far. Now for some serious testing!

[FrankcoProducts]

Hi, I repair boards for a living and most of them miller. This is a common code and it is usually, but not always, caused by a fault with the UI board (User interface). This board is the front panel board. I'm also in VT, small world.

[ArcTan]

That's cool! I've always been intrigued by electronics repair. I was going to go to college for electrical engineering but it would've cost so much.

[FrankcoProducts]

That's cool! I've always been intrigued by electronics repair. I was going to go to college for electrical engineering but it would've cost so much.

I'm self taught, studied college text books since I was in HS and I would breadboard most of the example circuits in the books.