How good is AHT (Apple Hardware Test)?

[booyahbooyah]

Macbook Air mid-2011, with El Capitan.

I'm dealing with a battery not available (x on battery icon) situation. Short story is that I poured water on the keyboard, old battery died, Macbook Air still worked without battery, got a new battery, and the new battery is giving the "battery not available (x on battery icon)" situation.

I thought there might be something wrong with the logic board or something. So I ran the extended AHT. There was nothing wrong.

My question is: are there types of hardware problems that the AHT cannot catch?

 

[cruisin]

Certainly. I suffered through many tests and reinstalls trying to fix an occasional crash while sleeping issue. Nothing was found until the problem got much worse, so I assume it started crashing while they were looking at it.

The test will check components like memory or GPU by sending specific instructions and checking for the correct result. If something is only partially broken then the quick test might not catch anything. The connection to the battery is likely corroded from water, so it appears like the battery is missing. The test would check if the battery can charge and if the capacity is still good but it cannot check if the logic board is ok.

 

[flyinmac]

My experience with the Apple Hardware Test is that it never found problems my macs had.

Hard drives that were failing, bad graphics cards, power supply problems, bad memory, etc.

I had more success with swapping parts than I did with the Apple tests.

The tests can only determine so much. If the faulty part returns what the test is expecting, then it won't catch it. That doesn't mean there isn't a problem.

I've used a lot of diagnostic software over the years. Typically observing the problem, ruling out potential causes, and manual troubleshooting is more productive.

I've tested a lot of known bad hardware components with diagnostic software. Rarely does the software locate the problem.

 

[maxsix]

I'd like to say it's a useful test. But repeatedly failing to detect a bad logic board and other actual faults makes me wonder.

In the end Apple replaced my entire laptop anyway.