I can't find a solution, so I ask for a council

Hi there,
my name's Giovanni, I'm from Italy.
I have a problem with one of my printers: a Hephestos 2 by BQ.
This printer always worked well, but now I have a problem that keep me out of working since two months ago (sorry for my bad english).
I will try to be as clear as I can in describing my issue.

1) nozzle did not warm up: problem was the thermistor but I've replaced the entire hot end, so a new nozzle with a new thermistor. Now, nozzle works well and reaches every temperature I set.
2) Nozzle AGAIN did not warm up: I've discovered that thermistor was not the only cause: the other problem was an interrupted wire (one of the two wires that take current from motherboard to the hotend), so I've replaced the wire but I did not find "the same" wire, I mean: original wire is large 2mm, I replaced it with a wire large 2,5mm. It's not a problem because nozzle warms up very well. But: to replace the wire, I had to displace it from the connector, ruining it, so I've made a connection by myself (I didn't find THE SAME connector to replace broked connector) between the two wires (red 2mm original and black 2.5mm replaced) and the two hotend cartridge's pins: well done, in fact nozzle keep warming up at the temperatures I set.

Now, the problem.

When printer used to work well:
1) if I want to change filament I set temperature and nozzle reaches it, so it search the Z "endstop" (the nozzle touch 2 times the bed until the sensor find the metal under the bed and a red led lights up) then it moves in front of the printer and it lets me to change filament. Then, it goes back to the start point, ready to start prints.

2) if I want to do the homing of all axis: nozzle reaches a pre-set temperature, then it search for the X and y endstops, then it search and find one point in the middle and the points on the bed's edges (2 in the front and 1 in the back), then it reach the start point, and it keeps the pre set temperature, ready to start prints.

3) if I want to print: I choose a file, then the bed reaches the temperature, then the nozzle reach for temperature, then the nozzle does the homing of all axis, then it goes back to the start point ready to start the print.

Whan the printer works bad, that's to say NOW:
1) if I want to change filament, just like the previous "1)", it goes on well.

2) if I want to do the homing of all axis it does every step of the previous "2)", but when it goes back to the start point, in the LCD panel I see this error:
ERROR WITH READING TEMPERATURE

3) if I want to print: I choose a file, but the bed does not warm up, then the nozzle does the homing but when it goes back to the start point, I read the same error in the LCD panel.

Now, I ask to you this:
seller of the printer does not answer to me and the BQ assistance does not exist for me.
The only 2 thing I can do are this:

1) smash the printer on the ground, again and again, till it becomes dust. Seriously.
2) try to replace one by one this 4 components:
--kit of cables from motherboard to the hotend (80€)
--inductive sensor for the leveling(33€)
--motherboard (134€)
--uninstall hot bed (printer comes without hot bed, it is a new component, it takes a firmware updating. Many people had problems with it, but the new firmaware's versions solved the bugs), but the site allows me only to update to the last version, it gives not possibility to uninstall the bed, so I do not know how to uninstall it.

I ask to you: what piece you would to replace first?

thanks to every one will answer to me..

P.S.: if there is some one from Italy, maybe we can interchange facebook contact and talk in chat live.

This is a great problem for me, my work is stopped and I'm going mad, seriously..

Giovanni

Edited 4 time(s). Last edit at 09/14/2018 08:37PM by johnleft.

You changed the whole hotend and you might have a different heater now.
I think, you only have to run a PID tuning for the hotend and the temp-error will be gone.

Because of the new nozzle, you might also have to adjust z-height ( sensor height ) again.

Quote

1) smash the printer on the ground, again and again, till it becomes dust. Seriously.

If you still want to do this, don't forget to take a video and post it
You might earn enough money with it to buy a new printer

1) smash the printer on the ground, again and again, till it becomes dust. Seriously.

what a child. Give the printer to someone deserving

Quote
o_lampe
You changed the whole hotend and you might have a different heater now.
I think, you only have to run a PID tuning for the hotend and the temp-error will be gone.

Because of the new nozzle, you might also have to adjust z-height ( sensor height ) again.

Quote

1) smash the printer on the ground, again and again, till it becomes dust. Seriously.

If you still want to do this, don't forget to take a video and post it
You might earn enough money with it to buy a new printer

First of all, thank you for your patience.
Listen, when I replaced the hotend (with an original one, the same for the Hephestos 2) I did immediately adjust the z-height. Only after that, I 've got this problem.
Can you tell me how to proceed to run a PID tuning? I've taken a look at the link but I'm really not sure where put hands..
thanks a lot

It depends on your hardware/firmware. But generally you connect your printer to a host program ( pronterface, repetier host etc. ) and send the PID command while the hotend is cold.
E.g. Marlin will process the PID tuning and return the new values. Then you have to store these new values in Eeprom. The gcode-wiki I linked you, has a few more commands regarding PID ( see M130 ff).

Quote
o_lampe
It depends on your hardware/firmware. But generally you connect your printer to a host program ( pronterface, repetier host etc. ) and send the PID command while the hotend is cold.
E.g. Marlin will process the PID tuning and return the new values. Then you have to store these new values in Eeprom. The gcode-wiki I linked you, has a few more commands regarding PID ( see M130 ff).

ok, I'll try. Thank you very much!