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-   -   V50 Electrics : Warning message / MOT (https://www.volvoforums.org.uk/showthread.php?t=282936)

waynegoldring Jun 13th, 2018 20:11

Warning message / MOT
 
I have a 2006 V50 T5 (2WD) and it had a fault with the alternator, this was replaced but now the dash has a warning of 'power system service urgent' or something to that effect, i can check the exact wording if needed.

Everything has been checked as far as the alternator goes, its charging, the battery is fine etc, nothing is causing any physical issues, so i would guess that the CEM either needs a re-coding to account for fitting the new alternator, or indeed it could be faulty and need replacing

The questions is, will that warning message fail an MOT? the MOT is due on the car, and i know the new rules mean that they wont let you drive away in a failure? so i am reluctant to either take it to volvo and potentially cost a fortune, or take it elsewhere and it potentially be stuck with them as it needs a main dealer to re-code it

I had read somewhere that it will fail an MOT on any warning lights relating to brakes, emissions or the engine warning light, so this warning falls outside of those categories? If anyone is an MOT Tester and could confirm either way that would be great, so i can work out the next step to take

Cheers

SwissXC90 Jun 13th, 2018 20:44

I am guessing you fitted a non-original alternator

These cars use intelligent alternators that talk to the CEM
If a plain old dumb alternator was fitted, it may charge the battery, but it won't talk to the CEM, and thus the CEM says something is wrong.

CEM won't need recoding for an oriignal Volvo alternator

Solution: fit an original Volvo intelligent alternator

SwissXC90 Jun 13th, 2018 20:50

And here's the technical description from VIDA:


For 5-cylinder engines the charging regulator (also called Alternator control module (ACM)) is connected to Engine control module (ECM) and communicates via LIN-communication. Engine control module (ECM) then communicates with Central electronic module (CEM) via the CAN-net when it comes to control of the alternator.

The central electronic module (CEM) has internal functions to regulate the voltage level and the power consumption in the vehicle. The central electronic module (CEM) controls the charge regulator via the engine control module (ECM) and therefore the current/voltage generated by the generator (GEN).

The generator does not initially charge when the engine is started. The charge increases successively when the engine has been started, controlled by Engine control module (ECM). When there is an increase in load at the generator, the increase from 0 – 100% takes place over the course of a few seconds (this time varies slightly depending on the operating mode the engine management system is in). This is to gradually increase the load on the engine during the start-up phase and to ensure the engine starts.
If the engine speed (RPM) exceeds idle speed (the exact engine speed varies depending on the mode the engine management system is in) during this delay, or if the progressive increase is interrupted, full charge is obtained immediately.

If there is no communication with the charge regulator, the charge regulator will not start charging on start-up. The charge regulator can however self magnetize the rotor and start charging. This occurs at engine speeds greater than approximately 2100 rpm. There is no charge engagement by stages with self magnetization, the generator operates at full charge immediately.
When self magnetizing has begun, the generator (GEN) also charges at engine speeds below 2100 rpm.

SwissXC90 Jun 13th, 2018 20:51

And some more:

Note! For vehicles manufactured from week 05 2006, the battery temperature sensor has been replaced by a new function in the central electronic module (CEM). The central electronic module (CEM) calcualtes battery temperature based on outside temperature, which is obtained from the outside temperature sensor.

Charging, 5 cylinder engines

When the ignition key is turned to position II (and III), information is transmitted from the central electronic module (CEM) to the charge regulator (alternator control module (ACM)) via the engine control module (ECM).

The regulator directs current to the excitation winding rotor and is then grounded via the regulator. When the current travels through the rotor a magnetic field is formed around the rotor. When the engine is started and the rotor begins to rotate, the magnetic field also rotates and then produces alternating current in the stator windings.

Alternating current is rectified when it passes the diodes and is then fed to the electrical system of the vehicle. The voltage obtained from the stator winding also passes to the regulator via the rectifier and affects the control functions.

The desired value for charge voltage is transmitted from the central electronic module (CEM) to the charge regulator via the engine control module (ECM). This value is based on factors such as the calculated battery temperature. The regulator then operates so that the desired voltage is maintained at the battery.

The charge indicator lamp in the combined instrument panel is controlled by the driver information module (DIM) via signals from the controller area network (CAN).

waynegoldring Jun 13th, 2018 22:00

It wasn't fitted by me, was taken in to a garage, so i am guessing then that they haven't fitted an original volvo one

SwissXC90 Jun 14th, 2018 06:30

Then you need to go back to them and complain

LizardOfBodom Jun 15th, 2018 10:59

Quote:

Originally Posted by waynegoldring (Post 2413975)
It wasn't fitted by me, was taken in to a garage, so i am guessing then that they haven't fitted an original volvo one

Alternators are known to go bad on T5's, same happend to mine while still at previous owner. He replaced it with reconditioned OEM one, no problems since. If you can find out if garage used a aftermarket replacement or recon OEM, it would give you some more info.


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