Amp Turn on/Protection Mode Issue

Hi, been on this site for years getting fantastic information that is ever so time consuming to try and locate anywhere else..
I have run into my first issue that i cant seem to find the answer to so i figure i would ask the experts.I will start with the gear in the car and then explain the issue.

Head unit Pioneer ahv 2550bt(parking break bypassed straight to ground),4 new door speakers(focal k2 front,hertz hcx-165 rear) tagged at the factory amp and wires ran to the trunk,stinger 4 gauge and interconnect,and finally a polk audio pda5000.5 5 channel amp that is running the factory sub till the weekend when i planned on building my box,And its all being installed in a 99 lexus gs300.

The amp started to go into protection as i was setting the gains,i thought maybe the amp was detecting clipping that i could not hear so i decided to turn the gains down a bit. worked good for 2 days and then the amp was in constant protection mode. that night i got out my volt meter and checked everything i could think of,power,ground,remote,impedance to all the speakers,checked to see if any of the speaker wires were grounded and all checked out, so i figured it was a bad amp from the factory....
Then today i decided to put a known good 2 channel amp i had in just to give me some music till i could send my am in for a replacement, got it all hooked up and nothing. I put my volt meter on the amp and with the head unit on i was only measuring 6.53 volts power to ground and 5.73 ground to remote, shut the head unit off and measure power and it goes up to 12.5 and the remote measured 11.73....
I am completely lost,i have never seen anything like that in all my years of installing, any help would be greatly appreacieated,thanks in advance,Jake.

sounds like a loose or bad ground(ground point not in a good spot or not sanded to bare metal) or a partially blown main fuse. i know the fuse part sounds strange but it is possible for AGU(glass cylinder fuses) to blow at each end and still look perfect in the middle. you will see normal voltage on the wire until you try to draw any power through it. to be sure, check the voltage on each side of the fuse while the system is on, if you see a difference in voltage then the fuse is blown. my suggestion would be to replace it with an ANL type fuse instead because this is a common problem with AGU fuses.

if this turns out to not be the case then unhook all speakers from the amp and turn it on, does it still turn on in protect? if so then your amp is likely bad, if it turns on normally start putting the speaker wires back on the amp one by one and see if it goes into protect. this will narrow down which speaker or wire is causing the trouble. it is possible that a speaker could only be grounding out while it is playing music and look fine at rest if the terminals of the speaker are too close to the door skin and possibly a screw is loose so that when the speaker vibrates it touches the door skin.

hope that will help you out, let me know what you find out.

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I vote for a bad ground too.

thanks for the detailed response, the ground was indeed bad the bolt had a locating shoulder on it and when tight there was about .005 clearance. I fixed that problem and hooked up my known good amp and still the amp is in protect with nothing connected but power and ground and then jumping the remote from the positive. I then checked voltage on bot sides of the fuse even tho i have an ANL fuse to start with.

Is it possible that i have ruined both these amps just from a bad ground?? seems kinda odd to me. on amp number 2 today after i had fixed the ground i drained the caps in the amp with my test light to do my best to get it to a reset point and it still went straight into protect.

If one of my speakers is grounded shouldn't i be able to detect it with the continunity function on my dmm? i have checked all 4 speakers 1 wire and both wires to ground on all 4 speakers and they all check out ok.

ok so what readings did you get when you checked for voltage? if you only have a test light then thats not a good enough troubleshooting tool. you need a digital meter that will give you an accurate reading of the voltage. also using a factory bolt as a ground for an amp isnt usually good enough. the ground needs to be connected to a flat area of metal with any paint sanded off down to bare metal screwed down tightly.

if you want to test for a bad ground then get a digital multi meter and put the ground lead to your ground spot and the positive lead to the positive terminal on your amp. if it is a good ground then you will not see a significant voltage drop. if your ground spot isnt a good spot then you will notice a big drop in voltage.

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I do have a digital multi meter i shortend it to dmm in mp post. i get 12.43 volts on both sides of my fuse and at the amp. My ground is sanded down to bare metal this is something i have done for 15 years of installing. The ground is flat right on the bare metal and the cargo strap point is on to bolted to the car with a 10mm bolt. voltage is 12.42 at the amp using either the end of the ground wire or the bolt head.

ok so if the voltage is fine at the amp and the ground is fixed and the amp still turns on in protect with nothing else hooked to the amp, that would seem to point to a bad amp.

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So now i have 2 bad amps just from a bad ground?? seems rather improbable... if both of my amps are bad could one of my sets of speakers caused this and if so how do i figure out which one if they all test good? i really have no desire to have another amp go bad. ive probably installed a 100 amps since i started doing this and probably 30 of them were mine and have never had anything like this happen and its a tad past frustrating to say the least.Thanks again for all of your input and advice.

id does seem unlikely that a bad ground would fry two amps like that, usually a bad ground will take a while to damage the amp or it will just go into protection mode. have you tried moving the ground to a different spot? not every place that is metal in a car is connected back to the battery, some panels are glued together and others are bolted together and may have a coating on them that keeps electricity from flowing. even though it tests fine with a meter it might be just good enough to allow some current to flow but when the amp starts to draw more current it feels the strain of that bad ground. if you have long enough leads for your meter you can test the resistance of your ground spot by hooking one lead to the battery ground post and using the other to test for a good spot with close to 0 ohms.

also are you testing this with the RCA's unplugged? sometimes if there is a problem with the RCA's it can cause the amp to go into protect.

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Once again thank you for all your input. I decided to try installing the Polk amp again after draining the caps and letting it sit overnight with nothing connected to it and it turned on, so i decided to hook up the rears first and it was still on so i then hooked up the sub and finally the fronts one at a time to see if it would go into protect and all is working. I have to admit this confuses me as to why the amp would not turn on normally once i fixed the ground issue. i understand why it would not work with the bad ground but common sense says when you fix the ground it should fix the problem... oh well guess i will build my box and amp rack and put this problem away. thanks again for your help its been greatly apperaciated.