How to test an AC/AC doorbell transformer? Ask questions and find answers to many subjects relating to electrics and electrical work

[brian_mk]

You have two choices: Either open up the cases and try to diagnose and fix the problem yourself or return both supplies for a refund or replacement.

It could be something simple like a connector or soldered joint.
Opening up the cases may be difficult or impossible if they are glued.
It would also probably invalidate any guarantee.

I think I would return both supplies. Both Amazon and CPC are pretty good when it comes to returning items.

[Mr White]

I have always been extremely careful about selecting the correct function on the multimeter

I'm connecting the output cables of the transformers directly to a multimeter, and setting the multimeter to AC/15V

But it is a 24v transformer?

In the past if I have set my multimeter to a lower range than the transformer is delivering the reading simply goes off the scale in the multimeter - it hasn't done any damage to the transformer. I have done this many times

Just because you always do something (wrong) does not mean it is correct.

There is nothing you can do other than replace them.