GTV - no sound....do I have an amp

[danny13]

weird problem trying to replace my stereo....I have a 2001 GTV Lusso, it had a silver alfa romeo head unit that didn't work.....has 6 speakers and sub.....and a multichanger in the boot.

I plugged in a new SONY headunit (CDX-GT50UI)....worked a treat (apart from a few speakers which I guessed must have loose connections)....unfortunately this headunit had to go into my van so I then tried to put an older SONY head unit in it (about 7 years old - CDX-M700R).....plugged it in.....power fine...but no sound....took it to a local ICE fitter, they tried their test head unit ....power but no sound. They said they would probably need £140 labor to take dash apart and figure out wiring....figured it shouldn't be that hard so decided to try and figure it out myself.

Went home and tried the new headunit again......and it worked!......so it seems my wiring will work with some headunits and not others......wondering if this something weird as both headunits have identical wiring connections (as did the test unit in the ICE store).....the one that works does have a slightly higher output rating 4 x 52W (the other has 4 x 50W)

My only conclusion is that maybe there is an amp somewhere that for some reason was blocking the signal from the old and test headunits!? Does anyone know where this might be?

[shiny_car]

amp or not, that shouldn't be the problem. though if there is a sub, i expect there is an amp.

what exactly did the ICE fitter test? did he test YOUR sony headunit (M700R) 'on the bench' or with another system? or do you already know it works perfectly?

the wiring MUST be different somehow. if there is an amplifier, then the amplifier needs to be triggered on/off via the remote output wire (on the headunit). is this connected up? it will be a blue/white wire on a sony.

the wiring basically boils down to:
1. powerwiring to run the headunit: 'constant'/battery wire + 'ACCessories'/ignition wire + ground
2. remote output wire: to trigger amp on/off
3. audio output: presumably via the speakerwire outputs; alternatively via the RCA preouts and RCA cables (but you make non mention of this)

any chance these 'speakers with loose connections' are causing the headunit to go into protection mode - and shut down the audio output? what is wrong with these speakers? blown or shorted wiring or what? that would be something to check (and presumably part the cost to troubleshoot).

[danny13]

thanks for that shiny car, you have made some very useful points.

The ICE fitter tested the M700R on the bench and also plugged in their own test headunit into the car.

I think I may have made a big assumption on the system in that i removed the front speaker cover and it seems aftermarket speakers have been fitted in the front, I've also noticed until the door sill leading to the rear what appears to be high quality shielded speaker cable (not the factory fitted cheap cable I would have expected).

I'm actually not sure if there is a sub I was simply counting the speaker covers (3 on the rear shelf), you've made a good point about the speakers so my plan of diagnoise is to put the function headunit back in and attempt to get all the speakers connected and working.

I have found one random wire with a male connector alongside the ISO fittings, which for the life of me I can't figure what is for, I'll take a picture and maybe someone can comment as to whether it is a standard connection (maybe its a phone mute - but I'm fairly certain I don't have the phone handfree setup).

Will post an update later as to how I get on, many thanks for the advice again.

[danny13]

4 hours later.....sorted!!!!

....there was indeed a loose speaker connection, I can only assume that 2 of the head units had some kind of protection system.......weird how the newest and most expensive didn't!

Many thanks for you advice!

[shiny_car]

no probs. glad it's sorted.