How to know if a cable is causing charging problems with my MacBook Air power adapter?

The short answer:

Most likely the root cause isn’t the adapter being too “strong” per se—it’s that smarter adapters require smarter cables. When a cable can't properly talk Power Distribution (PD) or confuses the adapter with poor wiring or passive multiplexing, it leads to the exact charging loop you’re describing.

A bit longer answer:

Your question touches on how power negotiation and cable quality come into play with USB-C charging, especially when dealing with third-party multi-use cables like your 3-in-1. What you’re seeing is a classic case of the cable not properly handling the USB PD handshake that the Mac power adapter initiates. The Apple 30W+ adapters speak USB PD and negotiate voltage and current with the device or cable. If the cable can't handle that handshake or misreports its capabilities, the adapter may back off, retry, or fail to supply power—hence the on-off cycling.

With a lower-powered adapters, there's no PD negotiation—just simple 5V output. These adapters don’t attempt to communicate with the cable or connected device about voltage and current levels, so even lower-quality or non-compliant cables can usually still pass power. But with the Mac adapter, if the cable doesn't support USB PD signaling correctly (or at all), the adapter may attempt negotiation, fail, and shut off power repeatedly to avoid risk—exactly what you’re seeing.

Here’s how you can test or confirm the issue:

• Use an MFi-certified USB-C to Lightning cable (like Apple’s own or a certified Anker one). If it charges fine from the same adapter, your Amasuki cable is definitely to blame.
• If you have a USB-C inline power meter, you can watch the voltage and current negotiate. With a failing cable, you’ll likely see it jump or drop frequently.
• Check if the cable is listed as USB-PD compliant or MFi-certified. Most 3-in-1 cables aren't and are mainly meant for convenience—not for compatibility with intelligent charging systems like Apple’s USB-C power bricks.

You would be best advised to discard the three-in-one cable - and instead use either (a) a certified USB-C to Lightning cable for charging devices with a Lightning connector, or (b) a certified USB-C to USB-C cable for devices that use a USB-C port for charging.

While your three-in-one cable might appear attractive from a convenience perspective, it will always be a compromise. Certified Lightning and USB-C cables incorporate electronic components within the physical connector - these providing active signalling to control the charging process. The three-in-one cable may not properly implement signalling or wiring standards - and is certainly not compliant with USB-C standards.

Your three-in-one cable will at best be a compromise and are a false economy. If it works at all, it may be unreliable - or may even cause damage to your expensive Apple devices. Why risk damage to expensive devices with a cheap cable that does not meet certification standards?