Hi all!

Today my girlfriend's 2005 Ka showed the red battery light on the dash. I am somewhat an experienced mechanic but very very rarely work on fords. A red battery often means a problem with the alternator as far as I know. So, i took my multimeter and started testing things. Car turned off ~12.4V (so the battery itself is good), car turned on ~13.5V with all the electrics off and ~13.5V with all the electrics on (lamps, heating, radio, fans... there really isn't much more in a 2005 Ka ). I know that 13.5V is somewhat low (14.2V-14.6V is the golden rule in my experience), some might even call it too low, but it was stable. So, the alternator is clearly charging the battery. I am thinking of voltage loss somewhere between the battery and the alternator or a corroded and bad ground, but would that be enough to turn on the red dash light? Could it be a loose belt, not spinning the alternator enough? Or just a worn out alternator... We tested the battery with the car running for around 15min, so I would even think that it is driveable. Thanks in advance for all the tips!

2 hours ago, redbatterygoaway said:

I am thinking of voltage loss somewhere between the battery and the alternator or a corroded and bad ground, but would that be enough to turn on the red dash light?

Yes it could be this. Without wrapping your hand in the belt with the engine running, try measuring the voltage directly off the alternator and see if you get a different reading to measuring at the battery terminals. 

2 hours ago, redbatterygoaway said:

Could it be a loose belt, not spinning the alternator enough?

You'd hear it squealing if the belt was slipping.

Have you checked the connectors to the alternator for corrosion and wiring for corrosion/ break in wiring. Common on the Ka. 

7 hours ago, iantt said:

Have you checked the connectors to the alternator for corrosion and wiring for corrosion/ break in wiring. Common on the Ka. 

So i've heared and read! I will look at the 3pin voltage regulator connector especially, that could cause these problems. I will definitely check back in later 🙂

10 hours ago, Luke4efc said:

Yes it could be this. Without wrapping your hand in the belt with the engine running, try measuring the voltage directly off the alternator and see if you get a different reading to measuring at the battery terminals. 

You'd hear it squealing if the belt was slipping.

I always did hear something from the engine bay, as if a belt was touching something every turn. Will definetely look at the belt itself... I might have been hearing this thing for all this time and now it has showed itself, possibly. 

Just to confirm, if i get a ~13.5V reading directly from the alternator it's for sure the alternator itself and not a voltage loss somewhere in between that and the battery. But if I am reading 14.2 or something it is voltage loss due to bad grounding or bad cable etc. 

I also tested the battery under 1.5-2k rpm load (no rev counter so it was bit of a guessing work) and the voltage went up to between 16 and 18V. As far as i know 18V could fry a battery... I am thinking regulator issues maybe? I think i will have her drive the car to me (25km), don't see why she wouldn't make it and then test some things as i said. 

Will check back in for sure! 🙂

3 hours ago, redbatterygoaway said:

As far as i know 18V could fry a battery... I am thinking regulator issues maybe?

Yes it will most definitely kill the battery at 18v, even 15-16v in constant use will kill it pretty swiftly. Like you said, sounds like a regulator issue or wiring to the regulator issue.

Change the girlfriend. 😂😂😂😂

57 minutes ago, iantt said:

Change the girlfriend. 😂😂😂😂

Hahahaha, good one!

7 hours ago, redbatterygoaway said:

I think i will have her drive the car to me (25km)

So it's not just in Wales that they use Km, now they use them in Oxfordshire !!

The far North is always the last to get anything new. Mind you I don't think I want any of those new fangled kilo things its bad enough trying to convert litres to gallons.

Update! The light now sometimes decides to turn off/on/off/on whenever it wishes so! So i tested all the voltages when it was off, and the battery with the car turned off was 12.4V and with the car turned on it was perfectly fluctuating between 14.2V and 14.6V, even under load! So the regulator is clearly working (when it wants, at least). I tested the voltage straight from the alternator at the cable itself and the reading is the same as it is at the battery, so there aren't any bad cables or whatever. I also checked the connections and pins, and it all looks good, got some photos. The pulley also checks out fine and the belt too! So what could cause these sudden faults?

I would say that one or even possibly two of the 6 diodes in the alternator rectifier pack is failing. If the vehicle is a 2005 and thats its original alternator then it is very likely on its way out. You can buy the rectifier assembly as a seperste item and replace it but due to the way its fitted it needs some high temprature soldering/brazing which most people dont have access to.

Service exchange alternator is about £80 available from many places.

On 8/4/2021 at 4:27 PM, unofix said:

I would say that one or even possibly two of the 6 diodes in the alternator rectifier pack is failing. If the vehicle is a 2005 and thats its original alternator then it is very likely on its way out. You can buy the rectifier assembly as a seperste item and replace it but due to the way its fitted it needs some high temprature soldering/brazing which most people dont have access to.

Service exchange alternator is about £80 available from many places.

So basically a new alternator... taking this thing apart and buying parts might just be more hassle and £ than just getting an entirely new one or second hand.

Try here, I've used them before.

https://www.ebay.co.uk/str/alternatorstartermotorparts

On 8/6/2021 at 1:31 AM, unofix said:

Try here, I've used them before.

https://www.ebay.co.uk/str/alternatorstartermotorparts

Are these some refurbishing services? Again, seems like a lot of hussle... Think I will just order a completely new one or a tested secondhand😔

I'm not quite sure I follow your logic, you are happy to buy a second hand alternator of unknown condition, might have done 100K miles but you think buying a refurbished alternator which has new bearings, new rectifier pack, cleaned, sand blasted, and comes with a warranty is "a lot of hussle" ?

7 hours ago, redbatterygoaway said:

Think I will just order a completely new one

That is one way to make sure its working, current Ford price is around £300