Tick toc fun with my clock

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serow
Joined: Thu 26 Jul, 2012 23:50
Posts: 22

  Z3 roadster 2.8

Tick toc fun with my clock

Post by serow » Wed 26 Jun, 2019 23:14

Help please
The clock/computer in my 1998 2.8 z3 works fine unless the car is not used for a few days.
I then have to reset it and it will work fine.
The face in fault looks like this - - | ..
Thanks Serow .

LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 26

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by LaRy » Thu 27 Jun, 2019 13:45

My guess is that you have a poor battery, but still strong enough to start the engine. But too low voltage to keep OBC (clock computer) data. I suggest that you check the battery voltage when the car has not been used for a while. The battery voltage should definitely never be below 12.4 volt. A poor battery is dropping the voltage rapidly if not used for a while. My guess is that the long time discharging is erasing the values in the OBC. For that reason it is good to follow up the voltage day by day, or make a professional test using heavy electric load.
I have a guess that you loose the values during the start of the engine. For that reason, I suggest that you turn on the ignition and check if the OBS is showing time correctly, and if it still does, after the big starting the engine. The engine start will reduce the voltage, maybe too much for the OBC. I've seen that in my Z3 when starting first time in the spring time, when the car has not been in use for 5 months and having a poor battery.
The OBC is using its own fuse, normally F31, maybe you have some corrosion! Check and clean the fuse.
The OBC has no battery or anything like that that explains why it keeps the value for some days, it has always continuous power from the battery through fuse 31.

serow
Joined: Thu 26 Jul, 2012 23:50
Posts: 22

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by serow » Thu 27 Jun, 2019 20:27

Thank you laRay
That is a very comprehensive list of checks
The battery could be getting low as it is at least 5 years old and like your car ZEDNA hibernates for the winter
Last winter the battery went flat for the first time and I put an optimiser on for the remaining months
I will run tests tomorrow night as it is a beautiful evening here my wife is out in the car
If you are interested I will report back tomorrow
Many thanks
Serow

LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 26

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by LaRy » Thu 27 Jun, 2019 20:37

Feedback is always welcome.

Fender2004
Joined: Fri 14 Aug, 2009 11:24
Posts: 900

  Z3 roadster 2.8
Location: Houghton-Le-Spring

Re: Tick toc fun with my clock

Post by Fender2004 » Sat 29 Jun, 2019 13:15

Try putting a charger onto the battery when you’re not using the car and see if it makes any difference.
Image

serow
Joined: Thu 26 Jul, 2012 23:50
Posts: 22

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by serow » Sun 30 Jun, 2019 19:52

Hi LaRy
It looks like your diagnosis is correct
Battery showing 12v but dropping to around 11.5 under load when starter engaged
Have not had battery checker on it yet but the readings from my meter tell a story
In case you’re interested my winter car is a SAAB 9-5 wagon Dame Edna my 10 th SAAB
I will keep you posted regards battery check
Many thanks
Serow

serow
Joined: Thu 26 Jul, 2012 23:50
Posts: 22

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by serow » Sun 30 Jun, 2019 19:57

Hi fender
Zedna won’t be used again until Wednesday
I have put a trickle charger on
Let’s see what happens then
Thanks for your reply
Serow

LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 26

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by LaRy » Mon 01 Jul, 2019 10:47

If you charge Zedna, and has less than 12.4 volt the next day, buy a new battery. No more investigation is needed. If you are down at 12.0 volt, you have 10% capacity, lost 90% over the night. 12.4 volt is equal to 60 %. 12.7 volt is equal to 100 %. A fully charged battery should not be down to 12.4 volt for may months. Why am I mentioning 12.4 volt so much? If you get below that voltage for a long time, the battery vill be harmed.

Nice to hear that you are a SAAB owner. Bad that the factory could not survive. I have always preferred the more boring reliable Volvo through the years. The Z3 is the opposite to drive, making my life fun.

serow
Joined: Thu 26 Jul, 2012 23:50
Posts: 22

  Z3 roadster 2.8

Re: Tick toc fun with my clock

Post by serow » Mon 01 Jul, 2019 23:00

Hi LaRy
The new battery is on its way will fit it at the weekend
My uncle owned the same Volvo 244 from 1978 until 2008
He no longer drives but still misses his blue Volvo
Thanks for your help
Serow

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