I think Tragicmagic is right.... I think you have a fried sub.

 

i have a alpine mrv1000 amp and the sub is a 12" s-type (4ohm)
its bridged, i dont know alot about this stuff so i hope i gave enuff info.

 

Like I said.. Based on the info you have supplied that amp is to much power for the sub and I would be willing to bet you have blown the sub.

 

ok so i took out the sub and hooked it up to my house amp and it cut out like in my car.
this could be a resistance issue with the sub ?

 

Your sub is blown. You will need a new one. If you plan on running it on that amp make sure the new sub can handle 650watts RMS or you will end up where you are now.

 

so bridging it wasnt the best idea. i looked up some info and it says
its 250w RMS per ch into 4ohms, so getting 2 12s would work pretty well?

 

That would probably be the best way to go.... Is that amp 2 ohm stable and if so do you know what the wattage is at 2 ohms?

 

no its not 2 ohm stable and at 2 ohms its 1000w peak. the sub is a DVC 4ohm so i thought it was smart to run just 1 coil, i dunno

 

Then I guess 2 4 ohms in stereo is the way to go.

 

Dude are you serious you only hooked up one voice coil on a dual 4ohm sub? You definetly have fried your sub. You must always hookup both voicecoils on a DVC sub or you will fry the sub. It is also highly recomended for maximum sub life that each coil gets the exact same power (a mono signal)
Is this your amp?
http://ampguts.realmofexcursion.com/Alpine_MRV-1000/
Think of each voice coil as its own circuit if the sub has 2 coils and is rated at 300rms that means each vc can handle 150rms so if you were running that amp bridged you were running 400rms (at 12volts) into one voicecoil that could handle 150rms.
Dual voicecoil subs are better paired with mono amps that can handle & work best at 2ohm loads. If you buy a new sub get a single 4ohm sub and run the amp bridged, overpowering is ok its called "headroom". If you are going to have your system fully cranked alot then look at getting a sub better matched for that amp but for everyday listening and driving you should be fine.