Heatbed not working

Hi everyone,
I have been having various issues with my Prusa i3 for as long as I have had it, and hopefully this will be the last one...
My heated bed one day just decided to turn off and not turn on again. After reading online, I found that it probably was a problem with the MOSFET connector on the RAMPS 1.4 that I'm using, so I replaced it with a spare one I luckily already had. It worked fine for a couple of days, then the bed stopped working again. I ordered a new, better MOSFET online and installed it. It worked fine, again, for maybe a day or two and then it stopped working.
Checking the voltage across the bed leads I find 0V, so there's a problem either with the MOSFET or with the fuses, at least that's my guess.
I don't think it's the MOSFET, since it's rated at well over 150A and I don't have that powerful of a power supply.
How can I check the fuses? I found an old thread on the forum saying that I could try and read the resistance between the + from the power supply and the + of the heated bed. I did that and got 4.6 Ohms. Is that good? Am I overlooking something?
Thanks for your help in advance!

The mosfet controls the negative line.
The 11amp polyfuse is on the +ve side.

You can bypass the fuse for testing if you want. Just wire the bed +ve directly to the power supply instead of the +ve d8 pin
The negative still goes via the mosfet so if it is still working it will still be software controlled.
(NB don't leave it without a fuse, that's a bad idea!)

NB mosfets are static sensitive, eg if you encourage your cat to rub itself all over the mosfet, the mosfet is going to die.

Hi again, sorry for bringing this up again...
First of all thanks for answering me in the first place.
I have been testing as you said, although I have done it only now since the printer had been magically working for a while... It sure looks like a fuse problem... Looking online I couldn't find any valid alternative to the MFS 1100 the board mounts: any suggestions? I guess I would need more than 11A*12V=132W of power dissipation, but other than that I don't know what to look for when choosing a replacement... Thanks again!

I think your best bet would be to grab another cheap Ramps 1.4 board ordering the right fuse from digikey will end up costing you more with shipping than grabbing a new board on Amazon. Can just keep your old board for parts and your good to go.

Those are thermal fuses reset themselves when they cool down never had one go bad though but its possible. I would make sure you have a fan keeping your board cool.

Fan is keeping heat under control, and it never gets warm to the touch. I'll probably do as you suggested, and just buy a new one. Hopefully it will work! I just thought those fuses would be easier to come by...

Most just put a thick wire link on the board in place of the polyfuse and put a real fuse in a inline fuse holder on the cable to the bed.