amp overheating

[Bronk93]

I purchased this amp http://www.crutchfield.com/p_777M407....html?tp=35782, and this sub http://www.crutchfield.com/p_777B12/...h=b12&skipvs=T from Crutchfield and the amp is overheating and going into thermal protect mode.

I did some tests using a volt meter and at the battery I get 14.23 volts, with the volume turned up and the system jamming I get about 13.60 volts at the amp. I thought maybe that it was a bad ground but since there isn't a significant voltage drop I dont think thats it. I have the rear channel bridged to the sub and a pair of alpine 6x9's running off of the front channel. The amp only gets hot on the side where the sub is connected. I have 8 gauge power and ground wires and 14 gauge speaker wire going from the amp to the sub. I have not upgraded any of the stock electrical system ground wires or alternator wires.

Where in the trunk is a good place for a ground? I just peeled up the carpet in the back, sanded a small space and used a self tapping screw. I'm not 100% confident in the ground so I'm going to relocate it anyway.

[hyunelan2]

If the amp is overheating, I don't think you are having problems with supplying it power. Where is the amp mounted? Can it breathe?

First thought that comes to mind is the 4ohm sub is too high of resistance for it to operate in 2ohm bridged mode.

Crutchfield's description of the amplifier has me a little suspicious:
75 watts RMS x 4 at 4 ohms (140 watts RMS x 4 at 2 ohms)
240 watts RMS x 2 bridged at 4 ohms (4-ohm stable bridged)

I would think that should be 240 RMS x2 bridged at 2 ohms.

[Bronk93]

Its in the trunk with nothing on or around it so it can breathe fine. I spoke to a few techs and one of them said that since it takes about 15 min for the amp to heat up enough to overheat that maybe the stock charging system is having a hard time providing enough power, not sure. All 3 techs confirmed that the rear channel is still 4ohm when bridged. The only thing I can think of is that the amp is faulty?

[hyundave]

Its in the trunk with nothing on or around it so it can breathe fine. I spoke to a few techs and one of them said that since it takes about 15 min for the amp to heat up enough to overheat that maybe the stock charging system is having a hard time providing enough power, not sure. All 3 techs confirmed that the rear channel is still 4ohm when bridged. The only thing I can think of is that the amp is faulty?

I had two rockford fosgate amps that did this exact same thing to me. I rewired my entire car trying to figure out what was wrong with them. I finally returned each one and was told they were faulty. Ended up upgrading and switching brands. Not sure when you bought this amp, but I would recommend returning it and getting your money back...

[smileymattj]

I agree with Hyunelan. The specs of the amp is not right. It's probably really 140w x 2 bridged at 4 ohms.

Most four channel amps can be stable at 4 or 2 ohms in four channels. But when bridged in 2 channels they are only stable in 4 ohms.

I don't think the amp can power 250w. Crutchfield is just listing what Sound Ordnance gives them.

Your power is fine, your ground is fine. With only 250w you're getting enough power to it. You kinda have to wire it extremely badly on purpose for ~200w not to work.

Try turning the gain & bass boost down on your sub channel a little. Or find a mono block for the sub, and you can use the four channel for your front/rears. Sub would work better powered by a beefier amp.

[Bronk93]

Yeah the 4 channel amp is class a/b and they aren't *** efficient as a class d for subs. I improved the ground and used a thicker wire from the amp to the sub and it seemed to not get as hot. Anyway, they are sending me a new one and if this one gets hot ill just return it for a monoblock.