I've been unable to complete installation and test the speakers that I've got because of the protect light. At first I thought it was something to do with the subs so I've temporarily removed them, but the protect light remains on. I've tried about 3 or 4 different ground spots, and am using zero gauge wire for both the ground as well as power from the battery. I've also tried a few different spots for the "other positive cable" (it runs from the amp between the positive and negative large cables... unsure of name, earthwire?, ...usually goes into back of deck to determine whether to turn on amp). I've tried placing it in different fuses in my car like power windows and power seatbelts because they have a higher amperage and I was worried that that could be the problem. I seem to be fairly lost as to what to do next. The only suggestions I have left require me buying a new fuse for the power cable as it could be blown, and/or getting the installation done professionally. Neither are really viable options for me because I'm poor.
Unfortunately, it sounds very likely that you have a defective amplifier. Usually you see a protect light on an amplifier because of an internal short, supply voltage too high, voltage too low, or speaker connections of too low impedance or grounded. If your speaker wires are completely disconnected, that eliminates the most common external cause of a protect light. Also, a protect light from the voltage being too high is very unlikely without the engine running (and an alternator problem). The "other positive cable" you're referring to is the remote input, and it won't cause a protect light no matter how it's connected. You'd need a voltmeter to do much more troubleshooting; a protect light can be caused by a very poor ground connection, or it's possible that a poor connection at the battery or fuseholder, or a defective fuse, is causing a severe voltage drop. However, based on what you've described, it seems most likely to me that your amp is defective.
Posted on Jun 07, 2007
You'd want to use the multimeter to test the DC volts at the amplifier's power terminals. Put the black probe on the ground terminal and the red probe on the power terminal, and look for the voltage while the system is on. If you get a reading of around or over 12 volts, and the protect light stays on, then it almost certainly means a defective amp. If the reading is well under 12 volts, then go back up to the battery and test various points of the power cable until you find the point where the voltage is dropping.
Ah, good; I'm glad you got it figured out. Enjoy your system!
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What would you recommend I test with the multimeter?
I know off hand that the fuse between the battery and my amp shows an extremely low resistance, but I'm even unsure as to what that signals!
I can only hope to assume that my connection at the battery is poor. It seems to be a really old battery and I may end up testing with a new one lying in my garage.
If it's any sort of help to know, my cousin had this exact same setup installed in his truck about 2 weeks ago and it worked fine. The only difference I can possibly forsee is that his ground and battery connections may have been better, and that the battery he was using was for an RV, rather than my tiny one for my sedan.
I checked a few things with the multimeter and noticed an errant reading (not 12v) coming from my battery wire. Turns out it was shorting out right inside the engine not 2 or 3cm away from the battery lead. All is well!
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