SOLVED UM2 Starting problem? Silence.

[vtlli 2]

When I press power button on printer makes short noise (barely hearable), after that main LED screen starts lighting as it should be. But there is no other sounds. It seems it ready to print (I didn’t try).

On previous prints machine started without issues but after finishing print during cooling there was no noise (internal fan?) at all.

What can be wrong with it and what can I check?

[gr5 2,167]

It's normal for it to be silent when you turn it on. Try heating up the nozzle and see if the rear fan (third fan on the back of the print head) comes on when the temp gets above 50C.

[vtlli 2]

Thank you for your input.

Let me describe the problem more.

After posting question here, I decided to go ahead and loaded big print for ten or so hours. All that time I was watching rear fan.

Normally, after switching printer on, third fan works constantly and starts to work making some noise and stops when printer switched off. Not like newer machines which needs 40C. I never updated firmware and done no electric/electronic modifications to printer. So there is no reason for different behaviour.

Yesterday I went for the big print anyway (needed it urgently). Back fan did not work. First hour – no visible spin. Second, third and so on. At the end of printing I gave up to watch it and was very surprised to hear noise when print was finished. Fan was working!

Today I loaded small print for few hours and back fan was working normally from first to last second.

Mystery!

What is happening to it? May be you came across with same problem before?

PS. When it was not working I traced all wire connections from mainboard to the fan and did find no fault. Voltmeter reading was 4.88V. I took 3xAA batteries to make 4.5V and connected to the fan – no spin.

[DidierKlein 729]

MAybe check the connection above the head inside the cable protection, and to the electronic card, this really looks like a bad connection somewhere.

Or maybe the cable is pinched?

[geert_2 557]

When it finally started running, did the fan run smoothly? Or does it make a lot of noise and a sort of grinding sound? If the latter, its bearings might be worn out, preventing it from starting? After a while, it does start, but only at low speed, and wobbly. I have seen this quite often in computer fans, in the old days of Windows 9x and Pentium I, II, etc...

If it are the bearings, replace the fan. You could lubricate the bearings to get a few more days/weeks/months out of it. I have done so by making a small hole in the silver cover plate with a needle, and then injecting a little bit of oil into that hole.

You could also pinch the cable and break it while reassembling the nozzle on an UM2, if it gets stuck between the metal parts.

[gr5 2,167]

I have also had my 3rd fan fail due to badly crimped connectors. The connectors are in the plastic sheath just above the hot end.

[gr5 2,167]

Oh and the "fan turns on at 40C thing" is hardware - not software. You and I both have the older UM2 with the older circuit board that has the fan always on.

[neotko 1,417]

Oh and the "fan turns on at 40C thing" is hardware - not software. You and I both have the older UM2 with the older circuit board that has the fan always on.

 

Technically is software/firmware and the 40C (editing marlin) can be adjusted to any number.

[gr5 2,167]

Okay, thanks for the correction @neotko  I guess the 40C is software controlled.  

But on my older UM2 circuit board there is no software control (the newer UM2 circuit boards have a new connector for the fan near the center of the board - the older boards the fan connects on the edge).

Edited November 7, 2017 by Guest

[neotko 1,417]

Okay, thanks for the correction @neotko  I guess the 40C is software controlled.  

But on my older UM2 circuit board there is no software control (the newer UM2 circuit boards have a new connector for the fan near the center of the board - the older boards the fan connects on the edge).

Older than 2.1.4 the hotend fan is just always on.

[vtlli 2]

Thank you for your suggestions.

It seems there was wobbly connection in wires between fan and mainboard. Since I posted question here I’ve printed 5-6 jobs for 12 hours each and was no problem.

Fan itself sounds nice, without strange noise which make faulty bearings.

When it was happen I haven’t any clue what was happen and was worrying printer going to die. But now when I found problem with you help I’m happy man.

Thank you.