Audio Systems: My car amp is acting up, sony xplod 1200w, rca inputs

Question
I have a Sony xplod 1200w amp in the trunk and a set of  12" pioneer IMPP subs.  I have the speakers wired in series and the amp signal is wired into the factory speakers using the high level input(not a low level converter to RCA).  The amp will come on and drive the speakers fine for a while and then the speakers wont kick(the amp is still on).  It will go into "offset mode" sometimes.  It has not gone into thermal mode yet.  Please assist!!!

Answer
You will run into a lot of issues by not using the RCA inputs.
I would not suggest a converter, either. The weakest link is always the downfall so do not too be alarmed when it 'goes south after the audio signal is sent to the amp in the worst possible way'.
It is kind of like buying a Ferrari and putting regular pump gas in it. It will probably start but it will give you trouble sooner than you would like it to.
Amplifiers are hard enough to setup properly when hooked through RCA's.
If an amp is not 'setup' properly of course many bad things can start happening (rca inputs or not).
If you think you wired it all correctly, try turning down the amp level potentiometer. Turn off any 'bass boost' and see how it does. You may need to re-adjust the crossover as well. Remember that the lower the crossover is set, the more you can turn up the amp level (within reason). Crossovers and levels can be confusing so take your time.
The box design for the subs will have much more to do with how loud the subs get [than whether or not the amp is set up to provide max RMS power].
If you reduced the amplifier power to 1/2 of what it is now.. you will only lose about 3 Db. That could easily make the difference in how long it will run [if it is now set 3 Db too high].
On the other, hand if the systems 'gain' is setup 12 Db too high, you will need to really reduce the amp level alot to get it to work correctly and for long durations.

Of course, be certain you have a good ground.
Be certain the load on the amp (combined speaker impedance as wired to the amp) is with in the Sony's tolerances.