Electricals Again (Radio)

[Grant Lenahan]

These radios have two powered inputs - one that is always on, and one that is switched.

Some power is always present to maintain memory, etc.

When you turn the knob, or push the button, or whatever you do to turn it on, one of two things happens_

1. a switch on the knob shaft connects the full power to the amp/etc.
2. a relay closes and does the same (remember, there is supervisory power to run a relay)

I would guess the on/off/vol switch, or the relay, is kaput.  Buy a new one or have it repaired (probably cheaper to get a new/rebuilt one). Search the web, including ECS tuning, force 5 ( a lister i believe)

If you want to check your wiring further, measure from a solid ground to the input to the fuse. Measuring "across the fuse" brings into question what potential the unpowered side is at. Is there a capacitor there with residual charge? Maybe.  Who knows. Dont measure there. Measure to a known ground potential.

Grant



On Oct 15, 2010, at 11:37 AM, mkb wrote:

> Hi All,
> 
> Well, I finally got the Bentley for the C5 and I was going to tackle the 
> open/short issue to the transmission control module.  However, the car is 
> running fine for now, so I figure I'll take a crack it after I get my radio 
> issue fixed.
> 
> Anyway, back to the problem at hand.  Symptoms are that the radio will not power 
> on.  If I pull the fuse (20A, position 37 in left fuse panel) and pop it back 
> in, the radio powers on.  BTW, I sometimes hear some crackling and have been 
> able to see a blue spark when putting the fuse back in.  After about 30-40 
> minutes of inactivity, when I try to power on the radio again, it will not power 
> on.  I have to pull the fuse and pop it in again to get it to power on.
> 
> So I pulled the fuse panel out and checked the back of the panel.  According to 
> the wiring diagram, I should have a red wire (+30) from the power supply coming 
> in directly to the fuse and a red/blue going out and this is what I see.  I 
> checked the connections into the fuse panel and they seem good and tight.  I 
> really wanted to pull them out and see if anything was loose but have not been 
> able to do so yet.
> 
> Also, I took a DMM and measured across the terminals for that specific fuse.  I 
> get between 10.5 volts and 11.75 volts.  Should I not see at least 12v?
> 
> Oh, also I can't seem to pull the radio out.  Seems to be stuck so it might be 
> hammer time if I need to check the wiring harness at the radio.
> 
> So I'm not sure where/what to begin checking.  Any suggestions?
> 
> --
> mohammed
> 99 a6 2.8q avant
> 97 1.8tqa
> 
> 
> 
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Grant Lenahan
glenahan at vfemail.net