V50: Grounding to body is sparking - Faulty CEM

[Skaftie]

Hey there!
I was driving a long distance trip yesterday, when i had drove about 7 hours the charging light lid up, I was about 15 minutes from my destination so i decided to drive on. Then suddenly all sorts of ligths in the dasboard started lighting up and then the hydraulic stearingwheel pump stopped working and then the car went completely dead (10 min from my destination) The car was now completely and utterly with out electrical power, it was like the battery had been disabled. I had to get my brother to tug the car the rest of the way. When I investigate the engine we se that the altinator was fried, and after checking online it seems that it was causing this. I changed out the altinator and charged the battery.
Now when i take the grounding wire from the battery to the car body it sparks like hell, checked with Ohm meter and there is quite at conduct between the positive and the bodyground. We removed the CEM from the car and then the sparking does not occur. Is there someone how knows this problem or has an idea what could be wrong with the CEM or its coublings, or perhaps something else.

[SwissXC90]

Remove CEM and disassenble
Observe for signs of damage
If a lot of damage is seen - burning, corrosion. etc: then you need a new CEM

The CEM contains tha car config and memory, and is coded to your car.
You must either buy a new CEM and have it coded by Volvo, OR get your CEM cloned by a company specialising in such cloning.

[Skaftie]

I have removed the CEM, but no corrosion or signs of burning, looks just fine.

[Clan]

Originally Posted by Skaftie

Hey there!
I was driving a long distance trip yesterday, when i had drove about 7 hours the charging light lid up, I was about 15 minutes from my destination so i decided to drive on. Then suddenly all sorts of ligths in the dasboard started lighting up and then the hydraulic stearingwheel pump stopped working and then the car went completely dead (10 min from my destination) The car was now completely and utterly with out electrical power, it was like the battery had been disabled. I had to get my brother to tug the car the rest of the way. When I investigate the engine we se that the altinator was fried, and after checking online it seems that it was causing this. I changed out the altinator and charged the battery.
Now when i take the grounding wire from the battery to the car body it sparks like hell, checked with Ohm meter and there is quite at conduct between the positive and the bodyground. We removed the CEM from the car and then the sparking does not occur. Is there someone how knows this problem or has an idea what could be wrong with the CEM or its coublings, or perhaps something else.

It is not unusual to get an initial spark when you fit the battery terminal , can you just quickly put it on and see if it starts ? The alternator failing should not have caused any electrical issues .. You could have fitted a faulty alternator which is taking a lot of power , try it with the alternator main wire disconnected ..

[Skaftie]

I bought exacly the same altinator as was before, same outlet, havent started the car since i changed it, the car is still completely dead, no electricity is working, but I am seeing a conduct beteween the plus from the cable coming from under the fusebox under the hood and the body/ground?,,, I tried to charge the battery with a battery charger when it was connected to as normal, but I got a fault error on the charger after a few minutes.

[Skaftie]

This conduct between plus and body/ground is eliminated when i remove the CEM from the car.

[SwissXC90]

With Unfortunately with the CEM removed you won't be able to do much with the rest of the car.

Tips:
Ensure battery is disconnected (both terminals)
Refit CEM
Connect battery positive
Connect a 21W automotive bulb between negative wire and battery negative.

The bulb acts as a safety shunt, allowing you to find shorts without doing damage
If it lights up brightly, then you have a short circuit or enough load to light the bulb.
A 21W bulb lights bright with 1.75A

The car consumes about 0.05A to 0.1A when the ignition is off and doors closed and no interior lamps on

When you "wake up" the car by opening a door, it will start drawing power.
In standby mode: awake, but no key in: expect enough draw to light the bulb.

If a direct short exists somewhere in the car, then the bulb will light up bright immediately.

If you have a direct short, start applying fault-finding logic:
What was happening just before the problem occurred?
Eg: If the Alternator went bad, then disconnect it and test again.

[Skaftie]

Thank you for your answer SwissXC90!
I mounted the new altinator, inserted the CEM unit. Went over the coublings from the battery and grounding to body.,, and vallua! it work like a charm now, i am wondering if the old/defect altinator was the reason for this problem, when i connected the minus it sparked just a little bit, nothing to the comparison to yesterday.. But the car is up and running now.

[Clan]

Originally Posted by Skaftie

This conduct between plus and body/ground is eliminated when i remove the CEM from the car.

I don't understand , you say you are touching the disconnected red battery + terminal to the ground of the car and you get a spark when the + pole of the battery is not connected to anything? Do you get a spark the second time you do this ?