820-3437 fan going nuts

[gadgetfix]

hey all i got a macbook air and although works fine fan spins up - just after boot.
Fan connector looks good - no damage.
I have tried another fan.
I have tried another io board.
R6060 R6061 R6065 R6010 all measuring good
Q6060 been replaced twice.
what am i missing?
thanks

[JohnB8812]

Does it slowly increase and stay on or does it just spin crazy automatically?

[gadgetfix]

slowly increase then stays high.

[JohnB8812]

So you have a sensor issue. Runs ASD 156 on this and see which sensor is failing.

[gadgetfix]

no errors in asd? crazy?

[2informaticos]

Did you try other trackpad and cable?
Also run some software for temperature indications.

[JohnB8812]

Hmm weird. Try without the webcam plugged in. If no change, try new trackpad and cable like 2informaticos said as well as a new battery. If still same issue, then has to be corrosion near SMC would be my guess

[2informaticos]

I forgot the webcam cable; ALS sensor is on the same...

[gadgetfix]

ok another issue i noticed, when battery is disconnected and reconnected. when i plug in charger fan will spin then turn off it will repeat this and on the 3rd time it will turn on and chime? is this normal?

[gadgetfix]

and also what is the best way to reflow smc? 350c? 7/10 airflow? should i remove silicon?

[JohnB8812]

Yes 3437 goes on off on off on. Best thing to do is remove the edge bonding then use around 250 celsius doesn't have to be super airflow to remove any junk from under it. If the same, then reflow at 430 celsius full air flow.

[2informaticos]

3437 MLB starts in that way, so is correct; valid for 3435 too.
Nobody can know the correct settings for your hot air station.
When talk about reflow, we give board temp as refference.
Reflow to burn crap under chip is doing at 180 degrees, no more.
You must know how to set your station, as its indication will be 400 degress maybe (or more), depending of distance and air flow too.
If you want to melt th balls, you will need to reach 230 degrees onboard; a small bottom heater can help a lot (I use MLINK 853A).

[gadgetfix]

thanks for all your valuable input. i can easily get things off the board at 350c, i use hakko fr-810b. I am just suprised there could be crap under smc as this has no previous history of water? but who knows?

i checked out the mlink 853a, that is very cheap! I have been looking at using preheater I really want something thinner but price goes $$$$$

[gadgetfix]

reflowed smc still spinning hard

[JohnB8812]

Hmmm this is a weird one. Try with just a known good trackpad and I/O board and cable plugged in. Let it boot all the way up with an SSD. If it’s still doing it, there surely must be a sensor that is reading wrong. Try booting into the OS and running HWMonitor on it to see if any sensors are reporting high