Possible Battery / Alternator issues?

fred246

I had trouble at a similar stage with my 1.9TDI. It turned out to be the alternator pulley. The belt was tight but the tensioner was jumping around like crazy. A new alternator pulley fixed it.

https://www.youtube.com/watch?v=rXehCcNzq_A

If you want to check your brushes and maybe replace the regulator you need:

https://www.youtube.com/watch?v=QtyP7AyZxwg

bigjl

Alternators don't charge the battery on tickover.

Which is why you a car will eventually flatten its battery when sat idling with other loads such as the radio or heater on.

A few years ago when the M25 was snowed in and cars where stranded overnight the AA/RAC had to jump start several vehicles that had been idling until the engine cut out.

In the OPs position I would first get hold of a decent battery charger and give the battery a proper overnight charge.

The alternator is only meant to replace what the vehicle systems use.

So if the car has had a flat battery and then jumped the battery is likely to never be fully charged.

A good overnight charge is cheaper than changing a battery or alternator.

forgotmyname

bigjl wrote: »

Alternators don't charge the battery on tickover.

Which is why you a car will eventually flatten its battery when sat idling with other loads such as the radio or heater on.

A few years ago when the M25 was snowed in and cars where stranded overnight the AA/RAC had to jump start several vehicles that had been idling until the engine cut out.

In the OPs position I would first get hold of a decent battery charger and give the battery a proper overnight charge.

The alternator is only meant to replace what the vehicle systems use.

So if the car has had a flat battery and then jumped the battery is likely to never be fully charged.

A good overnight charge is cheaper than changing a battery or alternator.

Your thinking of the ancient dynamo, The used to need a few revs before they produced any charge. An alternator charges from very low revs. Mine easily puts out over 14 volts at tickover and enough amps to overcome 70 - 80 amp load of heated screens and blowers on a cold morning.

If your alternator doesn't charge at idle then its faulty.

Retrogamer

forgotmyname wrote: »

If your alternator doesn't charge at idle then its faulty.

This is the thing. It will charge it tick over, but not before it's revved

I.e pre rev engine reads 11.9v on tick over.

Rev to 2000rpm, then drop back to tick over and reads 14.4v.

That's why i said above the alternator may be "tired"
It's not flat out stopped working but might be showing symptoms it's on it's way out.

Not sure what the amp rating should be on the 1.9TDi battery but old one was 480amps and new one is 720

forgotmyname

Is that the CCA rating? (Cold Cranking Amps)

Maybe the alternator sense circuit, Or it maybe the cars ECU detecting another fault and not giving the correct signal. Ive seen similar issues on cars with faulty fuel injectors. The revs will be too low initially as the ECU detects the fuel pressure being too low and gets stuck in a loop.

The actual Ah rating will be something between 60Ah and 100Ah usually.

Retrogamer

forgotmyname wrote: »

Is that the CCA rating? (Cold Cranking Amps)

Maybe the alternator sense circuit, Or it maybe the cars ECU detecting another fault and not giving the correct signal. Ive seen similar issues on cars with faulty fuel injectors. The revs will be too low initially as the ECU detects the fuel pressure being too low and gets stuck in a loop.

The actual Ah rating will be something between 60Ah and 100Ah usually.

Yeah that's the CCA rating.
Although the 480a one looks like the original battery i suspect it's not as 480a seems to low CCA for a 1.9TDi engine.

Think original one was 70Ah rating and new one is 80Ah

Same as this one

http://www.halfords.com/motoring/bulbs-wiper-blades-batteries/batteries/yuasa-12v-silver-car-battery-hsb096-5-yr-guarantee

arcon5

There's some real nonsense on this thread about the alternator not kicking out a charge at idle.

Well that's rubbish - they kick out charge all the time. It runs off the crank pulley on about a 2.5-3 ratio so an engine idling at 800 puts the RPM of the alternator at about 2000-2400. They typically start charging at about 1k revolutions.
Okay, granted the output is much greater at higher speeds, but it has a regulator anyway preventing too higher charge. You're looking at 14-15v depending on engine speed, even at idle.

If you're getting less than this, it's more than likely it's showing signs of wear. Even a worn alternator will give out the very high end of 13v at idle and can go on for a while before failing.

Of course the amount of charge back to the battery varies based on the load op puts on it, but with only things like the radio on, this isn't going to push the voltage anywhere near the point where current will be drawn from the battery instead. Frankly, if it's outputting less than 12.66V (ie fully charged battery) then there's a problem!

So lets do away with this urban myth that an alternator doesn't charge the battery at idle.

arcon5

forgotmyname wrote: »

If your alternator doesn't charge at idle then its faulty.

Okay - I guess my post was a little (lot) late. Only just seen this little gem

Retrogamer

Here's the readings again regarding alternator state.

Engine off with new battery - 12.9v

Ignition on with new battery 11.something volts

Engine started and idling at 1000rpm - 11.something volts (alternator not charging)
Rev to 2000rpm, alternator kicks in (14.4v) and continues to charge even when dropped back to 1000 / idle rpm

So unless i go a long journey where i don't hit 2000rpm it shouldn't be an issue.

arcon5

Sooner a later it will go mate. May last a few weeks, few months or whatever but will at some point. Diesels require twice the power from the starter motor than a petrol as well, they are not easy on the electrical system.
Is the battery light coming on at idle?