Protection light on suddenly

[da_guitarist]

I have a 99 Mercedes CLK430. It has a factory Bose system. I installed an Alpine R 12 and a Power Acoustik A2100D mono amp. As for wiring, here's what I did:

New Amp:

-Power/fuse from + battery term (4 gage, 80 amp fuse)

-Ground to bolt that battery is grounded to (4 gage)

-Remote from blue/white bose amp remote (18 gage, tap spliced)

-Speaker signal from grey/brown cables to rear deck sub, post bose amplifier (tap spliced 18 gage into rca plug input)

-12 gage speaker wire from amp output to sub enclosure

I was running the amp (2100w max) at only 30% or less with the amp gain knob, and it was kicking fairly hard, but nothing ridiculous or seemingly dangerous. Worked great for a while (only hooked up 1 day)...then suddenly it stopped working after a 20 min ride. the Protection light is coming on and I get no sound out to the sub. The sub isn't scratchy and shows 4.2 ohms w/ a voltmeter. So i think the sub's good

At first I thought maybe it's a ground problem with the input being amplified first and at a higher level than the chassis ground of the amp. Not so sure now. This is where it gets tricky:

I tried to fade the signal to the rear speakers using the head unit, and there is NO sound from the rear speakers now?! I wonder if the bose amp doesn't like this...or if i could have blown the rear speakers(bose factory "subs" on rear seat deck)?

When I get a chance, I'll rewire it to the INPUT wires to the bose amp (from head unit) and see what happens. Please don't tell me about my equipment *******. I put only about $170 total in parts and install items.

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[starkfu 10+ year member]

I am guessing that the entire marriage didn't like the high level inputs AFTER the factory amplifier. You really should use a LOC and then dump RCA's into the amp (assuming that you just plugged high level into high level inputs on the amp).

The next step would be to disconnect and return to stock to see if they factory stuff is still good. If it is, then get yourself a LOC and use RCA inputs to the amp.

 

[lostdaytomorrow 10+ year member]

I would use an LOC (Line Out Converter) and splice in before the Bose amps into a full-frequency signal.

 

[da_guitarist]

Where can I get a good LOC? Radioshack has a $17 one, and wal mart has a $15 or so one. Are the $5-10 ones on eBay any good? I don't want to spend over $20. Does this present a problem? Thanks!

 

[spoonraker 10+ year member]

So you drive a Mercedes, but you don't want to spend a lot of money...

 

[da_guitarist]

Haha...funny guy. it's old man! c'mon i'm on a budget. grad student here...

 

[starkfu 10+ year member]

use this

http://peripheralelectronics.com/prodDetail.asp?strProductID=573&strSearch=

peripheral pieces come highly recommended.

 

[spoonraker 10+ year member]

lol I was just kidding, I know it's a 99. Still...a Mercedes is still probably going to be more expensive than most cars for a lot of service/repair type of things. Anyway, I was just kidding anyway so it doens't matter.

You need a LOC as you know. I have absolutely know idea about the difference in quality between brands of LOCs.

 

[da_guitarist]

I bought one...it can be used several ways. I need to do line out, high to low, correct?

 

[da_guitarist]

I installed it and tried a few things. The rear speakers in my car work now. But the amp still shows the protection mode. I checked the voltage on the RCA plugs coming out of the hi-low LOC converter and it shows no voltage on any output (i tried all 4 outputs in case they were labeled wrong). Any other ideas? Are there any quick fixes to help amp problems like this?

 

[da_guitarist]

So I spoke with an electrical engineer who worked with Bose. They have differential signals, unlike most speaker wire signals. He suggests by inputing the differential load (with a floating ground), there was probably a point in which the reference voltage (+) compared to the ground was way high and overheated/melted the input chip/board on the amp. I wonder if that's repairable...