kac 929 shuts off

My sister in law has a Kenwood KAC-929 2 channel amp. It's "1000w max"... She also has a 12" sub that I can not identify. It has a giant spider and a giant stack of magnets and a logo I can't even describe on the face. There is no writing whatsoever on the speaker. Anyway, her amp will not stay on to save it's life. The ground and power is adequate. The amp is bridged and the 2 coils on the speaker are wired in series. I can't be sure of the impedance of the coils as they are unmarked and I don't have an ohm meter but with the coils in series the lowest it would be on any speaker I've ever seen is 4ohm... The amp shuts down constantly. I can't tell if it's going into "protect" per se because it doesn't have a light labeled protect. Even with the stereo off when I jump the power and remote terminals on the amp it turns on and shortly turns back off. Does anyone have any suggestions or experience with this line of amps? Or is the amp toast?'94 Ford Explorer / Kenwood KVT-815DVD / RF Power T1682C 6x8 (all doors) / RF Power T10001 / 12" Kicker L5 (x4) / Optima Yellow Top Battery

I would bet it is the impedance...I've seen speakers with .7 ohm coils

Does the amp play for a half of a second, then quiet for a couple of seconds, another half second burst, then quiet again?

try it with the amp not bridged.. or try it with all the gains turned down and see if it stays on then