Hardware The left rail on my NS is not working.

[SorataVP]

Hello, the left rail of my Nintendo Switch V2 does not work, I have replaced the rail 3 times now and it still does not work when attached to the console, it only charges the controller but does not recognize that it has a controller connected, it only shows me that it is connected wirelessly but ''charging'' I have tried the following:

1.- Replace the console rail 3 times
2.- clean the motherboard connector with isopropyl alcohol
3.- test other joycons on my rail and test my joycons on other consoles

I know this problem is rare, but I would like to know if there is a way to know what the problem is without having to remove the next suspect: the motherboard connector.

 

[Doctorbeefy]

What happened or what was done to the console just prior to this issue starting? This would help us try to diagnose the issue.

 

[SorataVP]

What happened or what was done to the console just prior to this issue starting? This would help us try to diagnose the issue.

Before the problem got worse, the joycon would disconnect from the console at the slightest movement, this is why I decided to replace both the joycon rail and the console rail, with the second replacement this serious problem began.

 

[Hayato213]

If you tried more than one rail then there is probably something wrong with the board, and the isopropyl alcohol, what percent is the alcohol content?

 

[SorataVP]

If you tried more than one rail then there is probably something wrong with the board, and the isopropyl alcohol, what percent is the alcohol content?

Yes, what I don't know is where to start on the motherboard, what to measure? it's OK? it's wrong?
99% is the percentage of alcohol according to the label

 

[Hayato213]

Is the switch modchipped?

 

[SorataVP]

Is the switch modchipped?

Yes sir, it behaves the same in both sysnand and emunand

 

[Hayato213]

Might be the Joycon handshake chip on the board

 

[thesjaakspoiler]

Might be the Joycon handshake chip on the board

There is no such chip in the Switch. The handshake is done in software.
Joycon's are connected (almost) directly to the Tegra cpu or they connect over bluetooth.
The charging state comes from the power management chip so that tells you at least the GND and +5v are fine.

If you replaced the entire rail already, then it might be the connector or some other damage like a crack or just some component missing.
It's a bit tricky but you could try to apply some downward pressure to the connector and see if the joycon gets recognized.
If it does, then it probably is a trace under to the connector gone bad.
I don't know if this is a V2 motherboard but maybe it helps :
https://www.tronicsfixforum.com/t/left-joycon-rail-not-recognized/2518
One user here had similar problems with his right rail and measures all all traces from the rail connector to the components via the connector.
(This connector on the rail : https://gbatemp.net/attachments/5_welding_points-jpg.140973/)

If you had a picofly or hwfly added to your Switch, there might be a chance that there is some damage around the cpu shielding that is causing this behavior.
A cut PCB trace or a component next to the shield might have been damaged when the shield was removed.
But that is a very rare case imho.