What happen if the car charger dont supply 1A, only 400 mA, if the device needs 1A?

I am trying to splice a cable (barrel port to a cigarette port). This is for a radio with 5V, 1A. In the package, there was a normal AC plug to barrel port. My plan is to just cut the cord and connect it to an old cellphone charger adapter. It is a really old charger, without any information on how many many amps it supplies. Since it is such an old charger it might only deliver a 400 mA. Can I safely test this out and if the radio work, can I assume that it worked flawlessly? Or do I have to check to overheating and stuff? (I do not have a multimeter)

• Get a multimeter. And a car have 12volt not 5 volt. And 400mA vs 1A probably not, and perhaps if the volume is low. Oct 1, 2017 at 17:02
• @MatsK hes probably talking about a 12v-5v old cellphone charger adapter. Oct 1, 2017 at 17:07
• @tobiasht You need to look over your question, and edit it. Oct 1, 2017 at 17:10
• Pretty much all phone chargers for the car are 5V, even really old ones. I can therefore be quite certain that this one is as well. The only thing that seems to change, is the amount of Ampere the chargers deliver. Im only wondering if it will be a problem if the radio pulls more power, then the charger is designed for (if it turns out that it`s only designed to deliver 400 mA. Oct 1, 2017 at 17:14
• You can expect failures to occur with shutdown under some conditions. Oct 1, 2017 at 17:20

1 Answer

You can't assume everything is ok even if the "radio" works.

• The old adapter may overheat and fail (dangerously or not).
• The "radio" could work on some conditions and perform wrong in others.