jl 450/4, 1000/1 issues

problem:
450/4 stops working after bass hit (almost like it is going into thermal protection). deeper the bass the longer the 450/4 takes to recover.
All is installed in a 2004 Avalanche, 220a stinger alternator, oem style battery big 3 done with 4g, 4g coming off of alt direrctly to battery (+ & -)

current setup:
JL C5 components & coaxials powered by a 450/4
2 12w3's powered by a 1000/1

Amps are wired with a trunk line of 2g with 250A fuse splitting down to 4g to feed each amp.

I spoke to JL and they think its a power issue, I have grounded at 2 points, one being a oem used ground point and another at where the seatbelt secures to the frame. All paint was removed from ground points.

The 1000/1 was just installed, It replaced a 500/1 which never gave the system any iussues.

Thanks for any help..ANY

I'd check to make sure the gains are set correctly.  I just fixed a 300/4 install done by one of the crappier local stereo shops just last week that had the same issue.  The gains and bass boost were up all the way, and it had an improper ground.  I fixed the ground and set the amplifier up correctly and it solved the problem.

the gains are set mid way, with the hi/lo switch set on low.

shoud all the amps have the same gain? How to properly set them other than by ear?

btw
the headunit is a Pioneer Z2

Thanks Again!!

You need to check voltage at the power and ground wire of the amp that is giving you problems.  You need to check this when the amp is at the point of cutting off.  You can touch the meter leads to the screws on top of the amp.  The power and ground screw.  Let us know the lowest reading you get. 

timvan wrote:

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the gains are set mid way, with the hi/lo switch set on low.

shoud all the amps have the same gain? How to properly set them other than by ear?

btw
the headunit is a Pioneer Z2

Thanks Again!!

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That head unit is rated to have a 2.2 volt preamp output.  With the amp switch set to low, the gains should be almost all the way down.  Check the manual that came with the amplifier for a description on how to set the gain on that amp.

I setup the gains just as JL list to do so, the gains are very low, less than 1/2 way up and I am still having the same problem..it actually seems worse now.
I have measured the voltage at the amp during the issue and the voltage did not drop on a analog voltmeter, I picked up a digital one and will try again today.

I even switched the 400/4 to a 2 speaker setup to see if that would help...NOPE

Thanks for all your help!

I measured the 450/4 at both normal and when its shutting down.
Normal voltage is 14.23 volt
Shutdown is at 13.92 volt, definately not low enough to be a power issue...

IDEAS?? Please Help im at a loss!!