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Rockford amp help troubleshooting


Knight_snook

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So I have a rockford fosgate r400-4d amp driving four speakers in my tacoma. It's been installed for about 3 years with zero issues and is not abused (still running stock speakers). The other day while driving listening to a podcast at normal volume the amp stopped outputting anything to the speakers. The amp never entered protect mode and still appears to be powered on (solid blue led). 

 

Here is a summary of the setup. 

 

Stock head unit 
Line output converter (2channel)
RCA input into the r400-4d (using 2 channel input mode)
I use the RCA passthrough off this amp as the input for my subwoofer amp (which is still getting signal and playing fine?!?)

 

What I've done so far...

 

-Checked all connections. 

 

-Power ground and remote are all good. yes inline fuse is good and the amp has no internal fuses. 

 

-Wires to speakers are good (not like all 4 speaker wires would go out at once anyways) 

 

-Speakers are good. When I installed the system I built a custom harness that taps into the factory head unit and output wire harness. I can easily revert back to stock by unplugging the custom harness and using the factory plugs behind the head unit. When I changed the connection back to stock the speakers work fine. 

 

-RCA input is good - like I said the passthrough to the sub amp is working fine. I also had the idea that the LOC could only be passing low freq signals so I plugged my ipad directly into the RCA amp input using headphone jack and still nothing. 

 

-I know that amp is putting zero power out to the speakers because there used to be a very slight hiss (barely noticeable) when nothing was playing. But now the speakers are dead silent. 

-I pulled the amp out of the truck and took it apart. Everything looks good to me nothing looks burned at least. I took pictures of the dirtiest connections but they seem solid to the board still. The amp never got hot to the touch even when played loud. 

 

-The only thing I can think is from the owners manual about using 2ch vs 4ch RCA inputs. See screenshot. The 2/4ch switch does seem sticky to me but I don't know if this could be the issue. Worst case the switch is bad and the amp thinks I'm using 4ch inputs but only have the front input connected. Would this really stop any signal from getting into the amp?  

 

-I think I have a way to troubleshoot the 2/4ch switch by simply plugging in 4ch RCA inputs. I'll get the front two from my 2ch loc. and I'll fake the two rear inputs fom the ipad headphone RCA converter. 

 

-I plan to try this tonight but after that I'm at a loss any help is appreciated.

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10 minutes ago, Knight_snook said:

I spoke to rockford on the phone today. They were no help and said the amp must be bad. Then they tried to sell me the newer model to replace it. Seems like a waste because it's probably one tiny component that has gone bad. 

You're probably right, but how can you find that one tiny component? 

I'm interested in how you fix this! 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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