My printer stopped printing during a few prints, and i found that the extruder had stopped heating, and the motors had stopped running. I checked the code, and nothing was wrong. My 5A fuse though, was extremely hot. I wanted to verify whether it was my fuse that had turned bad or there was some kind of short in my circuitry. With the power switched on, none of my appliances drew any current. However, the RAMPS board drew about 0.16 amps. Is that normal? If that is normal, does it mean that my fuse needs replacement? Because none of my loads seemed to draw unnecessary current. Thanks in advance.
As @Mikhail Z commented, it does sound like the fuse may be bad.
The first thing to do is put an ohmmeter across the fuse (with power off!) -- if you get high resistance the fuse is definitely bad. However, if you get low resistance that does not prove the fuse is good -- see @Tom's comments below re. polyfuses in particular, and how to disconnect from the rest of the circuit.
If you don't get lucky testing a fuse in-line, remove it and put the ohmmeter on it in isolation. Whether good or bad, it's good to put in a fuse-holder or socket, so you never have to de-solder the fuse again.
Some boards use auto-resetting fuses or circuit breakers, which might have more complicated ways of failing (you can always replace the part to be sure). I personally avoid auto-resetting for anything that supplies heaters; if there's a problem I want to intervene rather than letting it try again endlessly.
Since the heaters and the motors are both down, it's a good bet it's the fuse or something very early (that is, "near" the power supply). If it were a single motor or single heater, then the output control (typically a solid-state relay, or perhaps the logic controlling it) would be a better bet. Though unlikely, it's possible for two or more such controls to fail at once, so don't rule that out completely.
Let us know what you discover.
Its very likely the polyfuse is bad. In an ideal printer, given the heater cores and great deal of power, polyfuses are some of the worst things you can use. Polyfuses have a tendency to fail in "interesting" ways, especially around their trigger amperage. Fire is one of those failure modes.
Not only that, but if this is a noname chinese RAMPS 1.4, then you're also looking at 1/2 oz pour (it should be 1 oz or more for power traces) for the circuit board and cheaping on everything possible. I've a few boards like this that are a firetrap, along with a badly poured PCB heated bed. In that case, I would consider getting a better controller. If that's outside of your budget there is another way to do this.
Unsolder the polyfuses and put wire between them. Normally, this is unprotecting yourself. But we're going to fix that. Head to the local automotive shop and get yourself inline fuses (think of 2 wires with a fuse in a pill shaped device). You want a 5A and a 11A fuse. Or if you did the math and know better, get the fuses you calculated for. Now, make sure they're inline with the + side of the power.
You now have external fuses that you know are rated for the appropriate amperage, unlike polyfuses.