820-3462-A Thermal error fans running high

[cwalex]

The macbook boots up and runs. ASD EFI passes but ASD OS has 2 thermal errors "unknown result code -- test failed" and the fans are constantly running full speed.

This macbook had liquid damage, I replaced a couple of resistors near the SMC R5092 and R2502 and ran a jumper from pin2 of R5092 to PP3V42_G3H as that pad was gone. The only other corrosion I could find was a little inside the thunderbolt connectors.

I tried another heatsink and thermal paste and checked that U5570 has 3.3V on pin1. Could this be a problem with the SMC?

 

[2informaticos]

Run HWMonitor and see if any temp goes crazy.
Try known good trackpad board and flex.
Also test it disconnecting camera.

 

[cwalex]

I put the board in a spare chassis I have but the right io board is dodgy so it's left unconnected. Also left the camera disconnected.

Booted with a test macos and ran istat menus. It's hell slow and CPU is at 99%, temps are stable but the CPU die is not showing a temperature.

 

[2informaticos]

P-Bus reported as 12.19V is no good.
Check real voltage on the board (F7040).

 

[cwalex]

It's a hair under 12V according to the multimeter.

 

[2informaticos]

Check that voltage without battery connected.

 

[cwalex]

It goes up to 12.56V with the battery disconnected though.

 

[cwalex]

I had a look in the area near the SMC where I already ran a jumper wire and replaced a couple of resistors and found that the trace from pin 1 of Q5030 to R5033 was broken so I ran a jumper wire and now with the battery and charger connected I'm getting 12.3V on PPBUS_G3H. The fans are behaving normally now and the failing thermal test in ASD now passes. The 12.3V on PPBUS still seems low. Do you think it's something worth still investigating?

Thanks a lot for all your help as usual

 

[cwalex]

Actually, when I booted into macos, istat menus reports the ppbus @ 12.56V but it was reading a little high before.

 

[2informaticos]

Your multimeter can show erroneous value.
If SMC detects 12.56V should charge and recognize the battery; check that.

 

[cwalex]

Yeah it charges and recognises the battery just fine. All the ASD tests pass just fine now. Thanks again for your help. Can mark this one as solved.