06 Disco 3 Radio dead

guineafowl21 · Jan 22, 2019

Screen blank, no power at all. Fuses and relay OK.

I took the unit out and had a play, re-plugging ribbon connectors etc., and it came back to life when reinstalled. Now it’s died again and fiddling with ribbons didn’t work, so it wasn’t that.

Some googling revealed that removing fuse 53 and replacing 10 mins later can reset the radio and get things working, so I guess my playing at the bench had the same effect.

Anyone know the root cause? Battery and alternator are fairly new.

lynall · Jan 22, 2019

Have you checked the battery voltage with the engine running?

guineafowl21 · Jan 23, 2019

lynall said:
Have you checked the battery voltage with the engine running?

Battery voltage after an overnight rest is 12.47 V. Cold morning (-4 degC).

Drops to 9.47 V on cranking, but the car starts well.

Engine running voltage is 15.47 V. AC ripple under 30mV.

I would say that’s overcharging, but I’m not familiar with the disco electrical system.

jamesmartin · Jan 23, 2019

guineafowl21 said:
Battery voltage after an overnight rest is 12.47 V. Cold morning (-4 degC).

Drops to 9.47 V on cranking, but the car starts well.

Engine running voltage is 15.47 V. AC ripple under 30mV.

I would say that’s overcharging, but I’m not familiar with the disco electrical system.

try to see if voltage rises asyou rev it id say its over charging if its over 15

guineafowl21 · Jan 23, 2019

jamesmartin said:
try to see if voltage rises asyou rev it id say its over charging if its over 15

I popped the meter into logging mode and revved as you suggest - max voltage was 15.60 V.

It’s a mate’s car, but before I suggest he take it back to the garage that did the work, I wanted to confirm it really is overcharging, and not going into some some of boost mode for the cold weather.

My smart battery charger will take the voltage up to 15.8 V, but only to deliberately ‘boil’/gas the electrolyte to remix it - recondition mode.

lynall · Jan 23, 2019

guineafowl21 said:
Battery voltage after an overnight rest is 12.47 V. Cold morning (-4 degC).

Drops to 9.47 V on cranking, but the car starts well.

Engine running voltage is 15.47 V. AC ripple under 30mV.

I would say that’s overcharging, but I’m not familiar with the disco electrical system.

12.47 isnt really enough thats roughly 80 percent, fine on an older car but no good for modern electric hungry cars.

D3 charging at over 15 volts is quite normal, but 15.47 is higher than I have ever seen on mine.
I tend to do short 5 mile runs so my volt gauge shows 15.1 volts pretty much all the time and as yours is higher I would say the alternator is working overtime to charge the weak battery.
If I do any sort of run over 10/15 miles the volts will drop to 14.7/8 volts then after say a 100 miles non stop it will get to low 14 volts area.

Also what make was the alternator? anyhting less than a Denso unit has been known to casue all sorts of electical grief.

guineafowl21 · Jan 23, 2019

lynall said:
12.47 isnt really enough thats roughly 80 percent, fine on an older car but no good for modern electric hungry cars.

D3 charging at over 15 volts is quite normal, but 15.47 is higher than I have ever seen on mine.
I tend to do short 5 mile runs so my volt gauge shows 15.1 volts pretty much all the time and as yours is higher I would say the alternator is working overtime to charge the weak battery.
If I do any sort of run over 10/15 miles the volts will drop to 14.7/8 volts then after say a 100 miles non stop it will get to low 14 volts area.

Also what make was the alternator? anyhting less than a Denso unit has been known to casue all sorts of electical grief.

Not sure what make the alt was, and my mate wouldn’t know.

I agree it could be the alt working extra hard to maintain the crappy battery. Perhaps a hungry accessory switches off and the sudden release causes a voltage spike that bugs the radio? It’s quite clever to shut down the radio to protect it, but it would be cleverer to log the fault or at least have the unit restart after a pause, or have a reset button...

lynall · Jan 24, 2019

If you use a the camera on your phone you can see the alt make.

Have you tried a hard reset? basically disconnect battery, join the battery leads together for a few seconds and reconnect it all up, I think the idea is to discharge any capacitors on the car so every device has to start up from fresh.

06 Disco 3 Radio dead

guineafowl21

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lynall

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jamesmartin

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lynall

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lynall

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