Hello guys,
I'm bought a relay for Arduino, but my load use more current than my relay supports.
I know that I could use a second relay to solve my problem, BUT I'm thinking in a way of solve the problem without using another relay.
?
And how much current will your relay suffer when switching "on" ?
Certainly more than what your 200W Load will draw (16A),
as your 12V source has proven to supply that much.
And what's role of that miracle "Something to prevent short" ?
If that's a switch, your idea reminds me of the trick to test and eventually open a fuse by shortening a power line by your screwdriver.
Very bad practice 
Hello,
this circuit won't work as you expect. You need a switch in series to your load. This switch must be able to conduct and switch your load current. If you don't find a relay thats is big enough you can also take an electronic switch (MOSFET). But some experience with electronics is necessary.
What kind of load is it?
Elektrix
When relay go short, the source will be in short.
That's all the problem, that's why I put the "magic box" there.
The load is a MOTOTRBO™ Repeater, and the source is disgned for a repeater.
jgarcia:
When relay go short, the source will be in short.
That's all the problem...
And that's a real problem.
Why don't you take a relay that is able to switch 18A or 20A instead of the 10A relay in your diagram? Does your load have a logical input to switch it on and off?
Elektrix
Your "magic box" will have to limit the current to 10A for the small relay, it will then also limit it for the motor.
You could possibly design some form of crowbar circuit or switch the magic box or whatever, but the bottom line is that if your load draws 200W then you should just switch at least 200W, more really.
Get a bigger relay, job done.
Rob