V70: Electrical V70 2.0D Electrics fail, cuts out when warm at idle

[SquishyLemon]

Hi there,

A recently purchased V70 2.0D from 2009 has a weird electrical issue:

The car suffers from bursts of electric failure at idle (<1,000rpm) for split seconds ONLY when warm. All lights in the dash blink for a split second, same for the lights in the center console. Further the central locking is triggered. The feeling is like turning the ignition on and off for a split second.

SEE VIDEO

The car drives perfectly fine with no issue for about 15 minutes when cold and then, when warmed up, suddenly loses it's charging voltage from 14 to below 12V when the engine is at idle. Above idle the problem does not exist. If the car is kept in idle the electric issue persists and keeps on growing until the car cuts out completely but can be restarted immediately.

There is no check engine light. No codes in the ECU. I have scanned the car with my Launch tester and have only two seemingly unrelated codes for a "malfunction in the rear door locking motor, short to ground" (B110A11) and "positive heating coefficient in the heating system, Open circuit or short to ground" (B10EA14). Hard to tell if these have something to do with it...

Try No. 1:
Changed the battery with a known good one. Result: No change.

Try No. 2:
I have scanned the live values of the alternator voltage while driving (14V) and at idle when warm (>12V going down to 10V...). I have therefore concluded that the alternator has gone bad and exchanged it for a new unit. Result: No change.

Try No. 3:
I have routed an alternative ground from the battery directly to the engine. Result: No change.

I am suspecting some control unit issue (ECU or CEM), broken connection or water damage...

Any hints from your side?

Cheers!

[ShadeTek]

Looks like a bad connection somewhere. You will need two people to find this fault. One to go around the loom shaking it to see if the fault occurs or to tap the fuseboxes in turn to see if they have a loose connector. The other person will shout out when the dash blinks. Give it a little time and patience and you will find it.

[Simmy]

volvo cars are very sensitive to electrical faults 2 faults that show short to ground are definitely not helping your problem . a 10v signal will send the electical system in to a tail spin try to scan the car with vida as it can communicate with all the modules individually helping your search . also check the cem for any water ingress . un bonded windscreens are a known problem.

[SquishyLemon]

Thank you gentlemen for your replies!

So my issue does not seem to be one that happens regularly...

Still, I am aware of the water issues with the CEM and checked that first. Did not see any water damage, corrosion or even a wet carpet in the CEM area. The Windshield does not show any sign of flex (had that with an XC70 once).

Concerning the problem I find it weird that issue only shows up when warm and only after about 15 minutes. In fact it is that time focussed that the car starts twitching at the exact same location during the regular test drives...

Unfortunately I have no access to Vida. Yet, my Launch tester has the Volvo package. It finds and communicates with all modules in the car.

Will check the condition and voltage of the CEM and ECU next...