Glenn_

iTrader: (1)

Can you do me a favor people and check your alternator voltage.
Im thinking my alternator might be nackered.



Its only 13.71 volts and when im revving the engine the voltage just stays the same.

I dont know if its just a cossie thing lol cause most cars the voltage should be higher or less its just me worrying.

Paul_RS

iTrader: (4)

It should be 14.4v

Glenn_

iTrader: (1)

Yeh i thought it should be like most cars lol.

I just wanted to compare mine with others. Ive got a spare alternator which i will try.

RichieST

iTrader: (2)

The voltage regulator sometimes screws in to the back of the alternator, you might get away with just swapping that over.

costina

iTrader: (1)

14 volts on the secs on mine glenn with nothing on at idle.

Paul

Rob_DOHC

iTrader: (4)

Did you take that picture with a phone?

PS, some older Bosch alternators charge at 13.8v modern alternators are almost always 14.4-14.6 volts.

Normally a bad diode would mean a flat battery if left to stand.

Rob,

costina

iTrader: (1)

13.7 is not bad imo. Just keep an eye on it.

Rob_DOHC

iTrader: (4)

Agreed with the above. Also the regulator will have some level of temperature compensation, at cold you might find you charge at over 14v, with hot engine bay it will be lower.

Glenn_

iTrader: (1)

Yeh it was taken on my S6 edge.

Glenn_

iTrader: (1)

The reason im thinking its the alternator is cause the battery light is on ever so slighty and when im coming to a junction the light gets brighter.

Glenn_

iTrader: (1)

Ive just found a pic i had taken last year and the multi meter is reading 14.14 so the alternator mist be tired lol.

ajamesc

I've a brand new ford one to go on mine as my warning light was dimly on last few times I drove it. But when I removed my engine I found the main wire to the alternator had been rubbing on something and is corroded to fuck

Glenn_

iTrader: (1)

I was thinking about putting a wire from the alternator to the battery to see if this helps and doing this will eliminate the orginal wiring.

Ive checked the resistance in the positve wire from the battery to the alternator and that seems fine.

costina

iTrader: (1)

check for good earth at alternator body to chassis/ battery

Also check the small blue wire rear of alt which is connected to the warning light.

Paul

Glenn_

iTrader: (1)

I put a new earth lead from the battery to the battery tray on Saturday and this hasnt helped.

I will check that wire tomorrow when i have another look at it.

Tim Wharton

I would check the brushes only two bolts and it comes out with the voltage regulator a new brush pack is under Ł20 from your auto electrical specalist

Rob_DOHC

iTrader: (4)

That thing takes epic pictures for a phone!

Tim Wharton

Here is a picture of my old one so you know what you looking for

Glenn_

iTrader: (1)

Thanks. Its a good phone.

Glenn_

iTrader: (1)

Cheers Tim. Ive seen them on ebay.

Adam-M

I've got the same problem Glenn my battery light is on when I start up and it loses its charge rapidly on a brand new battery. When getting my alarm fitted the installer did say the alternator wasn't boosting voltage much when revving so I'm gonna buy a new one and drop down bracket.

RS 5tu

iTrader: (2)

If it was me would change the voltage regulator, maybe a cheap fix.

With the regulator when the brushes wear away you will still show 13.5+v but its the amps that will drop causing issues of battery light ect.

Glenn_

iTrader: (1)

Ive got a spare alternator that i was gonna put on the car. I took the bushes out to check them. They look a bit worn.

RS 5tu

iTrader: (2)

Here is the last one I did on my car

Glenn_

iTrader: (1)

Fookin hell lol. I think a regulator is only 20 quid so i might get one.

MARCOSWORTH

iTrader: (24)

I changed to a adjustable regulator and all is much better now

Gazzonator

iTrader: (9)

Try doing a volt drop check on the alternator cable mate as this can have an effect if there is high resistance on the cable.

With the engine running switch on lights, heater, heated rear screen etc, now with your multimeter set to volts, put one probe on the positive terminal of the the battery and the other on the main cable connection on the back of the alternator and see what you get. You shouldn't have any more than .5v reading. More than that suggests your cable isn't as good as it should be and you need to replace/rewire it

I checked mine a little while ago and was getting 14.3v at the battery.

cossynut2

Hi Glenn, it sounds like your alternator is on the way out as on mine a while back I noticed the red light didnt go out completely and was flickering on/off when going slow. The battery was not holding its charge either. I jump started it one day before taking it out and after a couple of miles noticed the indicators were not working and then shortly after it died on me. The battery was as flat as a pancake so I had to call out the RAC. When he came he checked the battery which was knackered and also checked the alternator which was knackered as well! He put a new battery in just so I could get home and I have now fitted a new alternator and battery and everything is back to normal. After 25 years and 105,000 miles I guess the original alternator had had enough. By the way the new alternator is showing 14.5 volts.

Glenn_

iTrader: (1)

Thanks for the info lad.

Cossie nut yours sound exactlly the same as mine.

cossynut2

It looks like it , either fit your spare one or get a new one.The new ones put out a higher charge than the original ones as well.

Glenn_

iTrader: (1)

The spare one i have is a 90Amp one. When im slowing down or indicating the battery light will flicker on.

Ive got a new regulator coming so i will fit this to my spare alternator and fot that to the car. If that one is no good i will just buy a new one.

cossynut2

Sounds like a good plan Glenn.

Adam-M

Is it eBay item 291221247920 that I will need? Where abouts in the alternator does it go?

Glenn_

iTrader: (1)

It says in the listing it will fit cossie.

Adam-M

Shit I should of scrolled down further in the add, cheers Glenn!

Dezzer

Check the voltage output direct from the alternator and check for bad earths glenn

RS 5tu

iTrader: (2)

Also voltage is only part of what you need to know, think of voltage as electrical pressure and amps as flow, You can have high pressure at different flow rates

You can still have 13+v and still not enough to charge the battery.

Think turbo, A T2 and a GT35 at 30psi will have the same pressure but different flow rates.

RichieST

iTrader: (2)

Resistance through your pipework, pressure of the air being forced through it and flow rate is all relative to each other.

2 different turbos with the same pipework, supplying the same quantity of air to the same engine will always produce exactly the same boost pressure.

And likewise, 2 different turbos, running at 20psi with the same pipework and engine, will be feeding the engine with the same quantity of air.

RS 5tu

iTrader: (2)

I was trying to make a simple initial reference, thats thinking too much

30psi through a macdonals straw and 30psi through a drain pipe is still 30psi but is still different,

I was trying to give a example people could relate to. In a but nut shell checking the Voltage of a alternator to see if its knackered is not going to tell you if it is or isnt its only going to tell you one that might be wrong.

martysmartie

iTrader: (1)

That's perfectly normal, modern cars are different.

A common problem is the wiring (like any old wiring) builds resistance, but you say you have measured the resistance anyway. You could measure the output from the alternator itself.

The light issue is quite common, it's because the voltage is greater on one side of the bulb. A high electrical demand can cause this to happen.

Martin