4 speakers from only front headunit outputs?

[From_the_Valley]

I'm helping my roommate figure out his setup in his new car, thing is he want to keep the stock HU. It's a nice HU (Nav, camera, bluetooth etc) but for some reason it only has the wires for front speakers and no back speakers, I guess because it's a van. We tried to run the back AND front speakers using the front signal and spliced that into high level inputs, but the 4 channel isn't liking it and goes into protect (seeing too low of an ohm load?). As soon as I take out the speaker wires for the back it's fine. We thought about using a 4 channel LOC and use the rcas but I don't know if that will solve the problem since theres still only the front outputs from the head unit, and I'd have to use just those going into the LOC. Any ideas besides another HU? If it helps he's running NVX components in front with NVX coaxials in the back off of a RF R300X4

[MrSkippyJ]

when you unhook the rear speakers from the amp it stops going into protect?

[From_the_Valley]

when you unhook the rear speakers from the amp it stops going into protect?

Exactly. I'm not sure why because it's still seeing the high level inputs the same as before.

[MrSkippyJ]

my guess is a short after the amp...have you tried the front speakers in the rear output?

[From_the_Valley]

I haven't but that's a good idea. It shouldn't be too hard to pull the wires and check for shorts since its a stripped down cargo van. My main concern though was if something was going wrong from hooking up the back speakers to the same wires as the fronts coming off of the head unit and feeding that into the amp.