Urgent Alternator question

[Sierra2]

Afternoon all

 

Firstly I apologise, I know this is not a car forum but I'm in trouble with a 2000mile round trip to France starting tomorrow. I only ask here as I know there are some very clever minds!

 

A mechanic recommend by a friend found a fault during a major service on the plug in diagnostic kit.

 

It/she is a 2007 Vauxhall Vectra 1.9cdti on 52k miles.

 

Normally I would have dismissed what he told me as nonsense, that being the alternator was only producing 12v. When I told him I put a meter on the battery terminals a week ago and read 14.63v (14.31v today interestingly) he straight away asked if I took the reading direct from the alternator.

 

When quizzed he mentioned something about a secondary charging circuit and canbus?.

 

Is it possible to get the reading I did at the battery and only get 12v at the alternator??

 

I'm not sure he was trying it on as I've been through 3 good quality batteries in two years (partly down to a period of non use) and Vauxhall did mention an error code (although no light on the dash) relating to the charging circuit about 7months ago during a key reprogramming. I dissmised this as I was happy with the voltage measured at the battery. Finally, a noise has recently developed in a week coming from the alternator pulley (much to my relief that it wasn't cambelt or water pump!)

 

 

Any thoughts, advice?

 

Thanks in advance, I'm slightly stressed as I've no option but to drive off for the Xmas break tomorrow....

 

Chaz

Edited December 19, 2014 by Sierra2

[Guest]

I have no knowledge of cannabis systems, but to my mind if there is 14+ volts across a battery I would expect it to charge same.

[Sierra2]

Just to add, if I recall what he said correctly... The battery was making up the extra voltage from the alternators 12v to get a higher reading?

[Emma b]

If it is a smart charge system, which it may well be, the alternator would only charge 'on demand', ie when the control module detects the battery needs it

[b0atman]

Engine off take battery terminals volt reading start engine does voltage increase ?

check alternator belt is tight enough.

[by'eck]

Afternoon all

Firstly I apologise, I know this is not a car forum but I'm in trouble with a 2000mile round trip to France starting tomorrow. I only ask here as I know there are some very clever minds!

A mechanic recommend by a friend found a fault during a major service on the plug in diagnostic kit.

It/she is a 2007 Vauxhall Vectra 1.9cdti on 52k miles.

Normally I would have dismissed what he told me as nonsense, that being the alternator was only producing 12v. When I told him I put a meter on the battery terminals a week ago and read 14.63v (14.31v today interestingly) he straight away asked if I took the reading direct from the alternator.

When quizzed he mentioned something about a secondary charging circuit and canbus?.

Is it possible to get the reading I did at the battery and only get 12v at the alternator??

I'm not sure he was trying it on as I've been through 3 good quality batteries in two years (partly down to a period of non use) and Vauxhall did mention an error code (although no light on the dash) relating to the charging circuit about 7months ago during a key reprogramming. I dissmised this as I was happy with the voltage measured at the battery. Finally, a noise has recently developed in a week coming from the alternator pulley (much to my relief that it wasn't cambelt or water pump!)

Any thoughts, advice?

Thanks in advance, I'm slightly stressed as I've no option but to drive off for the Xmas break tomorrow....

Chaz

Sounds like your mechanic is telling porkies. An alternator would never "produce" 12 volts since the batteries themselves in order to start car, would have a higher voltage than that. If you measure over 14 volts at the battery then the alternator is functioning. The differing battery voltages you got would be down to charge state, engine revs or even temperature.

 

This is not to deny that the ECU hasn't picked upon a minor fault that triggered the error of course.

[nicknorman]

Sounds like your mechanic is telling porkies. An alternator would never "produce" 12 volts since the batteries themselves in order to start car, would have a higher voltage than that. If you measure over 14 volts at the battery then the alternator is functioning. The differing battery voltages you got would be down to charge state, engine revs or even temperature.

This is not to deny that the ECU hasn't picked upon a minor fault that triggered the error of course.

Agreed. And modern alternators are controlled by the ECU, typically they will be set to a higher voltage after start, and then drop back to a lower "float" voltage. The voltage may well also be temperature compensated. Anyway if the battery is at 14.3 - 14.6v it will be happy.

[Pete & Helen]

Agree with those above. If your getting 14+ then the only thing that could be wrong (if he was right) is an intermittent connection, but I would think that you would get an indication with your charging light.

 

The only thing I can find regarding "Canbus" is that LED lights on cars could give an error to the sensors that check your lights are ok

 

This from another forum "LEDs only use around 20% of the power of a filament bulb, thus when they are fitted the car thinks the bulb is out/about to blow.

To get around this, some LEDs have resistors fitted which effectively burn up the other 80% so that the car thinks a standard bulb is fitted."

[nicknorman]

CANBUS is used in some modern cars to communicate between the ECU and the alternator. That is probably what the reference to CANBUS was about.

[pearley]

Alternators on Smart charging systems give various voltages depending on demand and can be as high as 15.5 volts. Such things as Heating, air conditioning, headlights, battery temperature are taken into account by the charge module to tell the alternator what to do. So, if measuring 14.4 volts at the battery I would say it us OK.

 

I have a couple of papers describing the GM system, although they are from the US, if anyone is really interested in how it works.

[Sierra2]

Thanks for the replies all. Would a test with headlights, fog lights, fan heater, demister etc turned on be worth a go?

[Albion]

All modern vehicles use a Controller Area Network (CAN) bus where various ECUs talk to each other, other devices and react to readings from sensors etc. As such, the modern alternator is also controlled as has been said above. If you are getting the required voltage at the battery then it can't be magiced out of thin air, it must have come from an alternator producing more than 12V at some stage.

I believe that some modern alternators in diesels especially may also have a free-wheeling pulley that minimises the effects of cyclical diesel engine crankshaft vibration on the drive belt wear so I am just wondering if that may be the source of your noise if your car has such beast.

Roger

[Sierra2]

Pete and Helen: I'm not sure how you got started on LED lights as I didn't mention anything.

 

However, I did change out the aftermarket Xenon HID headlights recently as I was fed up with one side failing approx every 6-8months on a two year warranty. The new kit threw up all manor of error codes, one or the other side failing to ignite, but then igniting when turning off and back on the headlight switch. This happended even after fitting a relay harness to take the power direct from the battery.

 

After a refund I've now gone back to the original supplier and installed a new upgraded set that's not proving problematic.

 

Don't know if related?

 

Chaz

All modern vehicles use a Controller Area Network (CAN) bus where various ECUs talk to each other, other devices and react to readings from sensors etc. As such, the modern alternator is also controlled as has been said above. If you are getting the required voltage at the battery then it can't be magiced out of thin air, it must have come from an alternator producing more than 12V at some stage.

I believe that some modern alternators in diesels especially may also have a free-wheeling pulley that minimises the effects of cyclical diesel engine crankshaft vibration on the drive belt wear so I am just wondering if that may be the source of your noise if your car has such beast.

Roger

Alternator until today, I thought ran off the cam belt but does in fact run off the fan belt (located in the same area) hence my confusion...

 

Chaz

[Sea Dog]

I agree with By'eck and Albion - If you're getting a reading of 14v+ at your battery, something is charging it and that something must be your alternator. If you haven't had any symptoms other than an intermittent fault read-out, I'd guess it'll probably do the same over the coming weeks as it has over the last. Sort it when you get back if needs be, and if it fails in the meantime you're in France and they have alternators too. Go to France and enjoy yourself - if the car starts tomorrow!

[EEng]

He's talking crap

 

If you have 14+ volts at your battery then the Alternator is working just fine

 

The battery cannot make up an extra voltage

 

I suggest getting another mechanic in future and tell him if he's as good at mechanical as he is at electrics then he should retrain to something like a tescos shelf packer

Edited December 20, 2014 by EEng

[Sir Nibble]

Lordy what a lot of guesswork!

Your engine starts, ergo, there is no problem. Modern systems have a networking around sub systems that makes even a good understanding of conventional alternator systems redundant. Charging is no longer a stand alone function, charging systems will shut down under command from a central ECU when the output is no longer worth the fuel and it's consequent emissions.

[Sierra2]

UPDATE:

 

Thank you all for your help and advice.

 

We did make it to France for Xmas but not before having to call out the RAC just two miles from leaving home!

 

About a mile away sitting at a set of lights I heard a strange sound that led me to turn off the radio and wind the window down to listen. I guessed this sound might be coming from the car sat next to us but couldn't be sure. As the lights turned green and we moved off I forgot about it and carried on for another mile. This time about 10secs after putting the handbrake on and in to neutral, a tremor came through the floor and the steering wheel getting stronger and stronger. It was scary in terms of thinking the car was going to shake its self apart but I instantly turned off the ignition.

Never have I experienced anything like that before.

 

​Sat with the hazards on, I chanced a restart a few mins later to move up onto the pavement to clear the lane we stopped in and everything seemed to be ok. Sticking my head into the engine I could hear a bag of odd sounds coming from the Aux Belt side including a ticking sound coming from the alternator that came and went.

 

I wrongly self diagnosed the fault as the water pump pulley (was the belt tensioner) as it seemed to be ratter-ling loose and on its last legs.

 

A very nice RAC man came out and told me that it was perfectly normal but double checked the nut torques on everything in that area to rule it out.

 

In the absence of finding anything else I decided to chance it on the offer that the RAC patrol would follow us from Barnes in West London down to the services on the A3 by the M25 junction (we could still get a tow back home at this point).

 

There was no repeat of the problem and following another check around at the services we headed off to Portsmouth and made out ferry. Still some odd sounds at idle and when cold but no repeat of that incident.

 

Bearing in mind the surge/vibration happened at a standstill I'm wondering if the engine started running on 2-3 cylinders for that moment?.

 

Regards

 

Chaz

[MtB]

I know that feeling of the floor of the motor seeming to be about to erupt. For me it was the polyvee belt driving the alternator, water pump steering pump and about four more things shredding itself to bits. As the cords flew off they battered the underside of the floor pan and once the noise went away the battery light came ON, the steering got real heavy and the engine overheated...

 

So I'm wondering if you check the width of yours you'll find half of it is missing.

 

MtB

Edited January 3, 2015 by Mike the Boilerman

[MoominPapa]

My first car was a Fiat 128. Fiats of that vintage didn't use a Bowden cable for the throttle linkage, instead there was a set of levers and bellcranks.

 

When the V-belt shredded on that, two things happened. First the bits got between the cam-belt and the auxiliary shaft pulley, which drove the distributor. It jumped a tooth and put the ignition timing 15 degrees out, resulting in very rough running and repeated backfires. Second, the flailing belt whipped against the lever on the engine side of the bulkhead, the other end of which was the accelerator pedal.

 

Having the car suddenly start running very loud and rough, and fight back against the loud pedal whilst doing 70 down Clive Sullivan Way in Hull was a memorable experience!

 

 

Mp.

Edited January 3, 2015 by MoominPapa

[Sierra2]

I know that feeling of the floor of the motor seeming to be about to erupt. For me it was the polyvee belt driving the alternator, water pump steering pump and about four more things shredding itself to bits.

 

 

 

 

When the V-belt shredded on that, two things happened. First the bits got between the cam-belt and the auxiliary shaft pulley, which drove the distributor. It jumped a tooth and put the ignition timing 15 degrees out, resulting in very rough running and repeated backfires.

 

Thanks for the replies gents but the belt is 100% fine and has been for the past 2000 miles since. Not to say it couldn't be a pulley or tensioner but I just don't get the intermitence of the sounds and the problems. Surely it would be a sound that gets worse and worse until it fails ?

 

Chaz