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Discussion Starter · #1 ·
Hey, so I’ve just installed a new head unit in my 2008 Honda Civic si sedan because I had no sound with the stock head unit. I replaced it thinking the amp went out and I didn’t want to replace the head unit because I was just going to use the new head unit to supply power to 4 speakers. I disconnected the subwoofer in the rear deck. But still no sound from speakers. Please help! I’m so confused!
 

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Does the Si have Premium Sound ? (I have EX Coupe, if its the same)
Factory HU feeds an external Amp.. then that amp (in Coupe located in Center Console just forward of the Shifter), feed's all the speakers including the Sub-Woofer.
Whats the Honda Part Number/Model Numbers on the HeadUnit ?

Your description is a little confusing, at least to me..
 

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Discussion Starter · #3 ·
yes my Honda has premium sound. But I replaced the old head unit with a Sony head unit, I was wanting to only use the 4 speakers and no subwoofer because I want to eventually upgrade to a 12inch, also my amp I believe is shot, but after some digging and asking other people, I think I may have a loose or cut wire some where
 

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You should have used an Amp ByPass harness from the New Head unit, remove the factory Amp or at least jumper around it...
Did/does the SI have front door & dash tweeters, plus 2 rear speakers plus a factory sub?

I have a problem in my car where I have front, but no audio in the rear.., so I've been all over the wiring..
 

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Discussion Starter · #5 ·
I unplugged the factory amp, but yes it has those speakers and sub you listed. But I think after some digging around it might be a wiring issue going to the speakers. I’m going to have to get a multimeter and test the wires.
 

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The factory amp is located under the seat in the sedan... the wiring harness is a bit different than the Coupe.
Where did you jumper/connect you speaker outputs from the new HeadUnit to the speakers ?

If you connected then at the output of the old HeadUnit connector, there is no direct connection to the speakers it all runs thru the factory amp... that amp has its own crossovers and output for the tweeters.

Out of curiosity what make is the factor HU, Honda part number and manufacturer part number ?
 

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Discussion Starter · #7 ·
So I’d have to run new wiring from my new head unit to the speakers?
and I don’t have the Part number on hand at the moment. I can get it for you when I leave to get breakfast, if that’s okay
 

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Running new wires from the new Head Unit to the speakers might be the easiest way.
2) Splice your HU out speaker wires to the wire/harness on the output side of the amplifier for each speaker
3) Find the various connectors between the Amplifier and each speaker and connect at that point.

The factory amplifier drives the Tweeters and contains the crossover for them.. if you want to keep the tweeters you will have to build/buy a crossover for the front.. easier and cheaper solution would be replace the door speakers with 2-way (Coax) speakers. You could replace the fronts with components, use the crossover that comes wit, but would have to run new wires to the tweeters.
 

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Hey, so I’ve just installed a new head unit in my 2008 Honda Civic si sedan because I had no sound with the stock head unit. I replaced it thinking the amp went out and I didn’t want to replace the head unit because I was just going to use the new head unit to supply power to 4 speakers. I disconnected the subwoofer in the rear deck. But still no sound from speakers. Please help! I’m so confused!
had the same problem when i put in a used head unit in my 07 si. after hours of trying to figure it out it was a blown fuse called “back up” it’s in the under hood fuse box. the fuse blew because i didn’t have a wiring harness so i cut the harness off to splice each wire together and not realizing the wires obviously would touch and that blew the fuse because i didn’t disconnect my battery so there was power through the wires
 

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had the same problem when i put in a used head unit in my 07 si. after hours of trying to figure it out it was a blown fuse called “back up” it’s in the under hood fuse box. the fuse blew because i didn’t have a wiring harness so i cut the harness off to splice each wire together and not realizing the wires obviously would touch and that blew the fuse because i didn’t disconnect my battery so there was power through the wires (reposted this because your question was mashed together with my reply)
 

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had the same problem when i put in a used head unit in my 07 si. after hours of trying to figure it out it was a blown fuse called “back up” it’s in the under hood fuse box. the fuse blew because i didn’t have a wiring harness so i cut the harness off to splice each wire together and not realizing the wires obviously would touch and that blew the fuse because i didn’t disconnect my battery so there was power through the wires (reposted this because your question was mashed together with my reply)
If you simply replaced a defective HU with a used one you should have been able to just unplug the connectors from the old unit and plug them back into the replacement.. why cut & splice.
 

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Actually 1st question should have been, does the new HU turn on ?
Lights, Action, No Audio ?

I guess the next question for you "Brgamer", is do/did you have navigation system... If so ignore all my comments about factory amplifier...
The question I asked about the Honda part & manufacturer model number would have answered that one...

Problem I have is no rear or sub audio/sound... I have narrowed it down to either the HU or Amp... I'm thinking/hoping it's the HU as the CD player has a mechanical problem and won't swallow CD's. Its a 50/50 gamble Honda service notes say swap with known good unit but for an individual that's an expensive trial and error proposition.
 

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If you simply replaced a defective HU with a used one you should have been able to just unplug the connectors from the old unit and plug them back into the replacement.. why cut & splice.
i tried wiring up an aftermarket deck before so that’s why i had to cut them
 

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So I had a similar issue(08 exl coupe). I thought the factory amp was done. The rear speakers didn't work at all. I had a extra pair of alpines. Tested in the rear and they had juice. The oem rear speakers & subwoofer burnt out. I found out the amp powers the sub & rear speakers, while the navi deck powers the front speakers. I ended up installing what is called a "converter". It taps into the rear speaker wires, and converts it for the RCA's so you can connect to a amplifier without replacing the factory head unit. I would just test the speakers 1st. Good luck
 

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Brgamer... after much research following wiring diagrams the SI and EX are very similar as far as HU and AMP but the actual wiring uses different routing, colors, and pin-connections in connectors is different,
My conclusion is that in your case splicing from the new HU you installed into the wiring you removed from the old HU might have been the correct/simple way to do the job. Disconnecting the amp was correct also, but you should have installed an Amp by-pass cable.. By disconnecting the the Amp you disconnected the speakers from the circuit.
I found an Amp By-Pass cable made by Metra 70-1728 (discontinued) that should work, but I'd contact Metra to verify, one post/ad-says 2006, another says select 2006 and up, another shows Metra 70-1727.
 
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