That's for the reply.👍 I'll take it out and have a check. No nothing piggy-backed, I've had the car for over a year and I'd say 1st 11 months no issues. 

It is like a gremlin with how it happens, completely random in frequency too. 

Hi Guys,

exactly same behavior here. After alternator change my Mk2 sony radio turns off on random bases. Immediatelly after alternator replacement I noticed that when car is in deep sleep, for example after night, it does not show anything on display (usually time) and it is also in deep sleep. When I turn engine on, it is still off. When I turn radio on, then sometimes everything is fine, it is on for hours, but sometimes it starts turning off. I also noticed that when this happens it shows "ONE HOUR" during startup, like if it does not have information that ignition and engine are on. But exactly after alternator failure and replacement. I am going to check wiring behind radio unit, but I do not think it is cause by loose connection.

Sometimes it is also really difficult to change time on radio unit, it keeps reseting. I believe it is synced with instrument cluster and there is something wrong.

Any ideas? Unfortunatelly it does not have any SD card support at all. Could it be AUX? 

Did you charge the battery for 12 hours after you fitted the new alternator ?

What is the battery voltage measured with a multimeter 1 hour after it has been parked.

How old is the battery.

On 8/23/2023 at 11:25 PM, unofix said:

Did you charge the battery for 12 hours after you fitted the new alternator ?

What is the battery voltage measured with a multimeter 1 hour after it has been parked.

How old is the battery.

No, I didn't.

I finally get to car and I measured 13.55 after 2 days standing still - not even unlocked, just opened bonnet and did measurement. After startup it shows classic 14.35. I also went throught whole fuse box  and nothing - all fuses look good.

 

 

19 minutes ago, Peetee said:

I finally get to car and I measured 13.55 after 2 days standing still

That's FANTASTIC 👍👍👍

So after standing for two days the battery state of charge was approximately 125% 🤣

Ok, so 13.5 V is not good, got it. I will try to get new battery. Any idea what cloud happen to battery that it shows so high voltage?

14 minutes ago, Peetee said:

I will try to get new battery.

Why ? The battery has a ridiculously high state of charge so it's not the problem.

You should get the charging voltage from the alternator checked, by an Auto Electrician.

I did one more measurement today. I do not know what happend last time that stand by voltage was so high. Today it was on standard 12.5 V before engine start and 14.3 when engine was running. After turning engine off it decreased back to 12.5 after some time.

 

What will Auto Electirican find except voltage? I am not asking because I do not want go, find and pay auto electrician. It is just my curiosity.

you need to reset the BMS, Battery Monitoring System. plenty of youtube videos on the process.

12 minutes ago, BigDaveL said:

you need to reset the BMS, Battery Monitoring System.

It's a 2005 Focus. BMS hadn't been invented 🤣