Rear amplifier outputs not working

[bigjd73 10+ year member]

I just received a used JBL GTO75.4 II i bought off of ebay yesterday and am having a problem with it. The first time I hooked it up i wired channels one and two to my front components and bridged channels 3 & 4 to an Elemental Designs 9kv.2. After reconnecting the neg batt terminal and firing it up I got sound from my front speakers but none from the sub. I then bridged channels 1 & 2 and 3 & 4 to run in 2 channel mode to my components and only got sound out of the speakers that were wired to the front outputs. Which i verified by switching which speaker was connected to which channel. I also switched the RCAs to make sure they werent the problem.

Any ideas on what else I should try/look for? Also, if the subwoofer had a short could it have shorted out the rear speaker outputs? I don't have a DMM on hand so I wasnt able to test it but was wondering if this was even possible. And I didnt think to check the fuses yet on it but I assume if one of them tripped the amp wouldnt even turn on.

Also, the diagram for bridging the amp says to connect the positive to the RR and the neg to the RL. Would it ruin an amp to run it to the neg of the RR and to the pos of the RL? I never did this, just curious as to why it makes a difference.

And finally, will it ruin the amp to run the comps of just the front channels, thereby using only the 2 front channels to run the front speakers and running nothing off the rear terminals? Contemplating doing this so I at least have some sound until I figure out something else.

Thanks

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[SRim23 5,000+ posts]

what HU do you have? some HU's you have to manually turn on the subwoofer preout. mostly alpines.

and if you ran RR and RL opposite you wouldnt hurt anything, you would be running the speakers out of phase.

 

[bigjd73 10+ year member]

Pioneer AVH-P3100DVD, and that is one of the things I did check.

 

[bigjd73 10+ year member]

what HU do you have? some HU's you have to manually turn on the subwoofer preout. mostly alpines.
and if you ran RR and RL opposite you wouldnt hurt anything, you would be running the speakers out of phase.

I don't mean switching the pos and neg, I just mean instead of connecting the pos wire to the pos of channel 3 and the neg to the neg of channel 4 like most 4channel amps call for, connect the pos to the pos of channel 4 and the neg to the neg of channel 3. Would this still result in it being out of phase?

Any other ideas?