V70 2.4 Petrol 170bhp 2003 - Alternator Overcharging

[robdeszan]

Hi All,
I had a random SRS Airbag Needs Service attention message appear followed (within a few miles) by a display of all sorts of lights on the dashboard. First thought, battery / alternator. Stopped and started the car again, this time none of the dashboard indicators (fuel, temp, rpm, speedometer) were working, the car was running fine. Switched it off again gave it a few minutes, started the car and all was looking ok, with just the SRS message. It was only a few miles from home so I turned back and measured the voltage on the battery:

car not running 14.56v;
Engine idling16.75v,
at 3000rpm 16.35v
heating/chair heating on 16.85v

This looks to me like a shot voltage regulator. The battery is just over one year old, the previous one failed after 7 years.

I have dug through the archives and found posts on replacing / removing the alternator but also a pdf showing how you could replace the voltage regulator with the alternator in situ, which I would like to try and do.

The car has 143k miles and I have not serviced or replaced the alternator in the 12 years of owning the car. How robust are they? Is it worth getting the regulator on its own or should I simply look at a reconditioned alternator which, given the mileage, ticks off all other potential points of future failures as well at this stage (bearing, brushes, diode). As a side note, the serpentine belt + tensioner was changed as part of a cam belt service a couple of weeks ago.

Thanks in advance!
Pat

[Dippydog]

Alternators are in my experience pretty robust things.Obviously if you change just the regulator there's no guarantee that something else won't go wrong with it tomorrow/next week etc.Depending on cost of a regulator I'd probably just swap that out especially as you're not paying garage labour rates.

[jnmonaghan]

Hi Pat- google - SiRobb videos A fellow forum contributor. There’re a video on changing the regulator.

[BlueRubber]

Check this forum members videos for how to replace the regulator in situ.
https://www.youtube.com/channel/UCET...9r708ezTOAKxLA

Also be sure to order the correct regulator for your car as there are two types used. I think yours will be the earlier type.
I think you will be fine just replacing the regulator, but if you wanted piece of mind buy a reconditioned unit or just check the condition of the alternator when replacing the regulator.

[oragex]

Originally Posted by robdeszan

Hi All,
car not running 14.56v;
Engine idling16.75v,
at 3000rpm 16.35v
heating/chair heating on 16.85v
Pat

With the engine off, you measure the battery however the reading is flawed because there's still a few computers/lights on and also right after shutting the car off the battery has a higher charge. A good way to measure the battery is after driving undo one battery cable, let sit 1h and read between the posts https://youtu.be/Tb3ACMO_9jA

A full new battery will show no more than 12.8v - slightly more if it's warmed in a hot summer day.

The voltage with the engine idling is too high indeed, assuming the voltmeter is working properly. At 140k miles is hard to tell the condition of the alternator but if the car was driven more spirited in the past, the alternator bearings may be approaching the useful life, same for the regulator brushes (and diodes). If you only think keeping the car for another 20,000 miles or so, perhaps replacing the regulator alone would do. You can always test the alternator bearings and clutch pulley once the belt is removed (see youtube how to). If you don't bring the alternator out from the engine bay, be sure to loosen up all 13mm bolts on the regulator (3 of them, one under the black cap) before removing the alternator from its bracket - these bolts are tight and hard to break loose while keeping the alternator from moving

[robdeszan]

Thanks a lot for all your suggestions!

It might still have been some residual voltage, true, despite letting the car sir for 30mins or so. Will try an measure again this morning now that the car has been parked for over 2 days.

That's the thing, I am not planning to let go off the car any time soon. Will have a chat with a local auto sparky see what they say / what quote they give me. I think they rebuild alternators themselves. A bit unfortunate with the failure timing everyone is pretty much closed until after the New Year now.

Massive price differences on reconditioned units as well on the web here in the UK. Can anyone recommend a reputable seller? How much should you expect to pay these days for a quality one?

[paddy74]

Originally Posted by oragex

[...]
A good way to measure the battery is after driving undo one battery cable, let sit 1h and read between the posts https://youtu.be/Tb3ACMO_9jA

As Oragex statet, let it sit for a few minutes (at least ten, better 30). But more important, if you do so, do not open/close anything during and after the waiting period. Every door you open, every window you move will start the electronics in your car again. So drive the car, park it, close all doors, open the trunk and then wait.

[Crash Bang]

How about testing the regulator/rectifier? You can do it in situ. Then go from there.

[robdeszan]

A quick update,

the car sat unused for over two days and the meter reading on a 12V battery- 14.75V - threw some doubts as to how accurate my multimeter was. Turned out the multimeter's battery was flat and gave incorrect readings. Replacing the mm's battery confirmed accurate/correct voltage readings.

I also monitored the voltage using my Bluetooth ODB Torque reader in all possible load scenarios, including extended driving, and the alternator appears to be working absolutely fine.

What threw me off was how random (I then assumed some voltage spikes?) the dash cluster behaved. Having ruled out the alternator, I am pretty sure that the Driver Information Module (DIM) / dashboard is playing up. While testing the car a today and it switched off, turned on, was a bit dim, was exceptionally bright, on but odometer/speedometer/fuel/temperature gauges not working - just an array of randomness. A tap on the top of the dashboard sometimes sprang things to life but by the time I was driving home the dashboard completely shut itself off.

The next step is to find someone in the UK who repairs DIMs I think. I'll dig through the forum.

I do appreciate all the suggestions, at least I feel I am now able to notice the red flags when it does eventually go bad!

[cheshired5]

Originally Posted by robdeszan

The next step is to find someone in the UK who repairs DIMs I think.

My DIM was repaired 3 years ago by this guy who has also done many others.