Technical OEM Delphi radio occasional no sound except for the subwoofer.

[gais]

Hi All,


I've been trying to solve this problem for a couple of years now. My wife's Punto Evo occasionally only plays sound through the subwoofer in the trunk.


The problem does not occur always, it's also not getting worse or better over time. It's best described as follows:

1. option 1:
2. switch on the ignition
3. sound only comes from the trunk
4. turn the ignition of and on until after a few tries the amp clicks on (the relay is somewhere in the amp itself, you can hear it click) and we have sound coming from all speakers

1. option 2:
2. leave the ignition off
3. turn the radio on with the power button
4. if no sound, keep pressing the power button until the unit switches off
5. repeat until it works, keep radio on and start the car

Things I've tried so far were to no avail:

1. Replaced the Delphi head unit, copied the EEPROM and it's working as it should. Problem did not go away.
2. Replaced the stock amplifier in the passenger foot well, also no luck.
3. Checked wiring loom on the back of the radio and amplifier.
4. Scanned the car for error codes with MultiEcuscan, both ELM as with the A3 - Yellow adapter cable. No codes popped up, everything seems fine.

Does anyone have more information on the workings of the Delphi F199 head unit or the Punto Evo audio system. Does it check the connections for errors before it decides to turn on? I really don't feel like opening all the door panels looking for a broken wire, but that is about the only thing I can think of now.

 

[Asteris]

It's either the +12V power cable to the amplifier, or the signal from the radio. Clearly amplifier fails to turn on. Just check +12V of the amp when the problem exists and if there is power, then it is definitely the signal wire.

 

[gais]

Ok an update from my side. After much trial-and-error I think I finally found the culprit. It started when the Punto sometimes would start up with only the subwoofer playing. No sound from the speakers. This gradually became worse up until the point that the speakers were not working at all.

I found a replacement Delphi HU. Had to clone the EEPROM for the car to accept it and the code to work, but to no avail. Next step was to replace the AMP and that seemed to solve the problem. At least for about a year. Then the problem came back and when switching back to the old amplifier, it did not seem to affect the chance of the amp not turning on.

As mentioned above by Asteris I started to suspect the wiring loom. Unfortunately it was not as simple as a switching wire. Checked the wires with a multimeter and they were all fine. I started to suspect a shorted wire in one of the speaker connections that would force the amplifier to turn itself off. I wanted to rule out the amplifier by taking it out of the loop, but the Punto with Interscope radio has a different connector and no direct way of plugging the speakers in the Delphi HU. Took me a few hours to decipher the electrics in eLearn and I found that all input- and output wires run through the connector at the back of the amplifier. I took the plug out of the amp and created a bypass for the speakers.

Finally the sound was back, and stayed back for the last two weeks. So the problem had to be within the amplifier. I took the thing apart and with the help of some spec-sheets was able to figure out the inner workings. Soldered some wire to to do a bench test and started poking around with a multi-meter and bingo, the amp was switching on (click from the relais) but no power was reaching any of the capacitors or components. After whacking the relais with the back of my screw driver power was back on. BINGO! A sticky relay turned out the be the problem in BOTH amplifiers. Just ordered 5 new relays on Amazon and will replace them as soon as they get in. I think this should solve the problem and I can enjoy some music in the Punto again.

 

[gais]

Out with the old, in with the new. Two Interscope amplifiers fixed for €5,- Bench-tested the amp and it works, this week back in the car.

 

[AndyRKett]

Out with the old, in with the new. Two Interscope amplifiers fixed for €5,- Bench-tested the amp and it works, this week back in the car.

The second rule of electronic club (the first rule being not to talk about electronics club) is to make sure you’ve got power to all your lives where you’d expect power to be, and then that you’ve got ground on the other side.
Fiat have a thing for dodgy relays see punto electric power steering problems, fortunately they are about the most simple and cheap parts to replace

 

[gais]

Fixed both amps for €2,- Back in the car and working like a charm...