OEM Sound System - No sound from radio, CD Player volume low

[jeffreygebhart]

Sound system is oem (okay, there is a Parrot bluetooth installed by a prior owner. Don't know how to use it, don't know passcode. That's a problem for another day :frown:.) When turned up full volume, no sound from radio and cd player plays but the volume is low. Sent out head unit for repair. Just reinstalled head unit and same problem exists. Does anyone have any thoughts on this (before I go out and buy some new Bose speakers)?

Thank you!

 

[Old Guy]

The OEM Bose system has three separate amplifiers (2 - door & 1 sub woofer). If the head unit is OK, it would be exceedingly low probability for all three amplifiers to quit at exactly the same time. I don't have my service manual handy; but, my recollection is that the amplifiers are powered up from an external relay which gets an on signal from the head unit. If the relay fails or the supply fuse blows, then all three amps are dead. The only thing that I am uncertain about is that the amps are all class D amps, so in the absence of power there should be absolutely no sound. However, the amps do have feedback circuits from the speaker terminals back into the input so perhaps there is minimal signal leakage through the feedback circuit that could result is slight sound.

I suggest that you check right at the amps for power. If you have some headphones you could also check for the presence of the line level audio signal to make sure the head unit is operating. Getting at the door speakers requires pulling the interior door card off which is a hassle. I think it should be easier to get to the connector on the sub woofer. If there is no power to the sub then chances are there is no power to the door amps.

Check the wiring diagram in the shop manual to find the pin arrangement for the plug on the sub.

 

[jeffreygebhart]

The OEM Bose system has three separate amplifiers (2 - door & 1 sub woofer). If the head unit is OK, it would be exceedingly low probability for all three amplifiers to quit at exactly the same time. I don't have my service manual handy; but, my recollection is that the amplifiers are powered up from an external relay which gets an on signal from the head unit. If the relay fails or the supply fuse blows, then all three amps are dead. The only thing that I am uncertain about is that the amps are all class D amps, so in the absence of power there should be absolutely no sound. However, the amps do have feedback circuits from the speaker terminals back into the input so perhaps there is minimal signal leakage through the feedback circuit that could result is slight sound.

I suggest that you check right at the amps for power. If you have some headphones you could also check for the presence of the line level audio signal to make sure the head unit is operating. Getting at the door speakers requires pulling the interior door card off which is a hassle. I think it should be easier to get to the connector on the sub woofer. If there is no power to the sub then chances are there is no power to the door amps.

Check the wiring diagram in the shop manual to find the pin arrangement for the plug on the sub.

Can you tell me where the amp relay is located? If it is with other relays, which one is it? Etc...

Thanks!

 

[metsuki]

the amp relay is also powering the radio antenna if i am right. if your antenna go up when you power the headunit then it is not the relay

 

[jeffreygebhart]

The antenna does extend when I turn the head unit on, so I guess the relay's okay. The head unit was recently repaired, so I guess that leaves the speakers, but they still operate, albeit with very low volume, when operating the cd player only (the radio doesn't work, period).

Thanks for the response, metsuki! I appreciate it!

 

[Old Guy]

the amp relay is also powering the radio antenna if i am right. if your antenna go up when you power the headunit then it is not the relay

You are only partially correct. The signal form the head unit which controls the power antenna up relay is the same signal which controls the power amplifier relay. However, the antenna does not get its power from the power amplifier relay. It has a separate 'up relay' in its housing and it gets its power from a separate fuse. As a result, the power amplifier relay can be dead or the fuse supplying it can be blown and the antenna will continue to go up and down when you switch the head unit on and off.

The fact that the antenna goes up and down is a good thing because it indicates that the power up signal from the head unit is working.

 

[cjn944]

I am having the exact same issue. No sound from the radio but if you switch to the CD player and turn the volume all the way up you get sound. Brand new speakers and amps from Bose, and I got a spare head unit that will replicate the same problem? Any suggestions, my instinct tells me to start checking the power to the amps, but I am open to suggestions.

 

[Old Guy]

Any suggestions, my instinct tells me to start checking the power to the amps, but I am open to suggestions.

Yes, easiest 'first thing' to do is check the power amp relay and the fuse that is supplying the power amp relay. The fuse supplying the power amp relay is #51 in the main relay box. The power amp relay is in relay box B on 1991 cars; but, be warned that Honda moved the relays around during the production run. Your power amp relay might be someplace else so check the service manual to confirm your relay location.

Also, does your power antenna go up and down? The power amp relay gets its 'on' signal from the same wire out of the head unit that signals the power antenna. If the power antenna is not doing its thing it may be the absence of a power on signal from the head unit.

 

[cjn944]

Yes, easiest 'first thing' to do is check the power amp relay and the fuse that is supplying the power amp relay. The fuse supplying the power amp relay is #51 in the main relay box. The power amp relay is in relay box B on 1991 cars; but, be warned that Honda moved the relays around during the production run. Your power amp relay might be someplace else so check the service manual to confirm your relay location.

Also, does your power antenna go up and down? The power amp relay gets its 'on' signal from the same wire out of the head unit that signals the power antenna. If the power antenna is not doing its thing it may be the absence of a power on signal from the head unit.

Update on this. Checked fuses and relays and everything is normal. Power antenna moves up and down as it should. When I plug in the second head unit that is on loan to me I get full volume and CD player and AM/FM radio. I mistated this in the above post. Problem with the loaner head unit is that I get a very load "pop" sound when turning the head unit on or off and also when I switch sources from CD to AM and FM. Full disclosure, I have only the drivers side and subwooder that are brand new from Bose. The passenger side if still on back order from Bose and I am being told late August to Sept before I will have it. I don't think this would cause the problem, but I am open to suggestions at this point. I bought the car from cmc140 here on prime and the next step is going to ship the radio back to him to test in his car and rebuild if he can duplicate the same problem I was having.

 

[NSX2398]

You might want to check with Prime member BrianK who is a knowledgable NSX owner who was offering a rebuild service on amps and head units. If swapping out the head units fixes the problem, then I'd think the other head unit is still bad even though you said it has been repaired. The head unit only sends line-level signals to the amps so if you're getting proper volume with the loaner head unit, then the amps must be getting power and doing their job. The popping may be coming from the Parrot unit installation although I have no experience with that device. I switched over from BOSE dist'd amp design to a centralized amp (plus an SOS iPod adapter) and I get the occasional pop when turning on so I just leave it on CD (to access the iPod) and leave it powered on.