Hi

Driving 2007 1.9tdi Octavia

Recently it's been sluggish to start cold and warm sometimes. With a jump it's great so I'm guessing that rules out starter.

The battery is less then one year old so I thought alternator.

When I spoke to local garage guy said he would change the battery after I told him symptoms.

I tested battery with multimeter...12V engine off. 14.1 engine running

Also tested alternator to best of my ability with red lead on the cable goes from Alternator to the battery and black lead on alternator housing and got 12.1V

From what I read it should be more like 14.2V there

Anyone think I should buy new battery or does it seem as it is the alternator is bad?

Is there a guide on here for replacing alternator on here??

27 minutes ago, huwants2no said:

Hi

Driving 2007 1.9tdi Octavia

Recently it's been sluggish to start cold and warm sometimes. With a jump it's great so I'm guessing that rules out starter.

The battery is less then one year old so I thought alternator.

When I spoke to local garage guy said he would change the battery after I told him symptoms.

I tested battery with multimeter...12V engine off. 14.1 engine running

Also tested alternator to best of my ability with red lead on the cable goes from Alternator to the battery and black lead on alternator housing and got 12.1V

From what I read it should be more like 14.2V there

Anyone think I should buy new battery or does it seem as it is the alternator is bad?

Is there a guide on here for replacing alternator on here??

 

You want to be reading from the main red cable on the alternator to earth.

 

Your measuring the battery voltage doing it on the body, not the charging voltage.

Edited 18 June, 20241 yr by Blue8793841

15 minutes ago, Blue8793841 said:

 

You want to be reading from the main red cable on the alternator to earth.

 

Your measuring the battery voltage doing it on the body, not the charging voltage.

There was a black wire held on with nut. And another cable with the usual bag plastic connector. I disconnected it and touched multimeter to one the 2 pins on the alternator and got the reading off that and the metal case as an earth.

Does that make sense:)

Can't see 'main red cable' anywhere. Just those two in the pic

Where the black cap is that wire you want to be on

I wouldn't rule out starter motor too, they are common. I've seen people put new aftermarket starter on and have the same fault. Switched to 2nd hand genuine one and it was fine.

18 minutes ago, Blue8793841 said:

Where the black cap is that wire you want to be on

Just tested from that and it's between 14.3-14.4 so that seems to be ok.

I think one of those cables running back toward battery was chewed by rat. Just noticed some corrosion. I'll try get a pic

The chewed cable with bit of green corrosion on it is behind front left headlight

Edited 18 June, 20241 yr by huwants2no
Add info to pic in post

If it looks to you as though water has got into the cable then replace it.

Major sign to look for is the internal multistrand copper conductor turning black.

Doesn't look great. That wire goes from alternator to starter and battery, might be worth replacing the harness to start with.

49 minutes ago, pikpilot said:

If it looks to you as though water has got into the cable then replace it.

Major sign to look for is the internal multistrand copper conductor turning black.

The copper wind inside the alternator?

Bloody rats jesus

38 minutes ago, Blue8793841 said:

Doesn't look great. That wire goes from alternator to starter and battery, might be worth replacing the harness to start with.

Any ideas as to where I might find a diagram of the wiring?

Thanks for all the replies btw

8 hours ago, Blue8793841 said:

I wouldn't rule out starter motor too, they are common. I've seen people put new aftermarket starter on and have the same fault. Switched to 2nd hand genuine one and it was fine.

Yep I would say it is foolish to rule out the starter.

 

I had this issue a few years ago and the starter was the cause.  It was malfunctioning and draining the battery (and ended up ruining it).   Car started fine on leads though, but that is not exactly a long-term solution!

10 hours ago, huwants2no said:

The copper wind inside the alternator?

No, I was refering to the chewed cable in the photo.

6 hours ago, JamieH86 said:

Yep I would say it is foolish to rule out the starter.

 

I had this issue a few years ago and the starter was the cause.  It was malfunctioning and draining the battery (and ended up ruining it).   Car started fine on leads though, but that is not exactly a long-term solution!

Ok. Why would the starter work grand off jump leads on another cars battery but not work properly off my car battery?

That's what I don't get re starter motor

Thanks

Edited 19 June, 20241 yr by huwants2no

That alternator output wire doesn't go to the starter motor, it goes direct to the leftmost (as viewed from front of car looking into bay) big vertical fuses at front of engine bay fusebox.

Wire gauge depends on alternator rating fitted, 16mm squared unless it's a 140A alt, then its 25mm sq.  Looking at your earlier pic, it appears to be a 140A alt.

 

 

Edited 19 June, 20241 yr by Breezy_Pete

SA1 is the fuse it goes to.

1 hour ago, huwants2no said:

Ok. Why would the starter work grand off jump leads on another cars battery but not work properly off my car battery?

That's what I don't get re starter motor

Thanks

In my case, the problem with the starter motor wasn't that it was not working in the sense it couldn't start the car, but it had an electrical fault (for more detail track down my mechanic from 2018!) that meant it put too much load on the battery, and the car was progressively harder to start until eventually the battery was flat and all the electrics died one day.

 

However, when starting the motor with jump leads, you're connected to a car where the engine is already running and the battery is charging, so the faulty motor still gets sufficient power to start the engine.

 

Basically the cause of my issue was the starter motor, but the actual symptoms were in my battery.

On 19/06/2024 at 13:26, Breezy_Pete said:

That alternator output wire doesn't go to the starter motor, it goes direct to the leftmost (as viewed from front of car looking into bay) big vertical fuses at front of engine bay fusebox.

Wire gauge depends on alternator rating fitted, 16mm squared unless it's a 140A alt, then its 25mm sq.  Looking at your earlier pic, it appears to be a 140A alt.

 

 

Ok thanks for that and the diagram. Whatever it is it's annoying as hell. 330k miles on this girl,maybe time to move on

On 19/06/2024 at 13:49, JamieH86 said:

In my case, the problem with the starter motor wasn't that it was not working in the sense it couldn't start the car, but it had an electrical fault (for more detail track down my mechanic from 2018!) that meant it put too much load on the battery, and the car was progressively harder to start until eventually the battery was flat and all the electrics died one day.

 

However, when starting the motor with jump leads, you're connected to a car where the engine is already running and the battery is charging, so the faulty motor still gets sufficient power to start the engine.

 

Basically the cause of my issue was the starter motor, but the actual symptoms were in my battery.

Ah rite. Sorry I wasn't thinking much past the obvious. But I see now there can be other faults but similar battery symptoms

I got a new battery so I'll put that in and see. Will try tidy up the chewed wire as best I can but I guess over time damage will occur along it.

Used to be a great breakers near me where the guy would let you bring tools and remove parts you wanted. Closed down tho sadly

Thanks for the help

Ok. Removed battery tray and few bits for better look around.amongst other things discovered that the wire I referred to earlier,one that goes into fues box at SA1 I believe is nearly cut thru completely. I'm guessing and I mean guessing that this would cause battery drain when car sitting.

I'm hoping I can replace it.

It runs from that fuse box SA1 across to the pump under the alternator. Is that the power steering pump?

Would anyone know is that a cable that I can order online or dealer only.

I'll try add a pic of where it connects...

It's going to the alternator output stud, surely? Black plastic cover over the nut?

 

Measure how long it is, buy a pre-made 25mm squared cross-section bit of cable with the necessary size crimps on each end.

(M8 at alt end, M6 at fuse, maybe?).

Must be loads of sellers on ebay selling various or custom lengths with ends to your specifications. 

2 minutes ago, Breezy_Pete said:

It's going to the alternator output stud, surely? Black plastic cover over the nut?

 

Measure how long it is, buy a pre-made 25mm squared cross-section bit of cable with the necessary size crimps on each end.

(M8 at alt end, M6 at fuse, maybe?).

Must be loads of sellers on ebay selling various or custom lengths with ends to your specifications. 

No it's not that one. Goes to a 2 pin connector on whatever is directly under the alternator on my model. It has metal pipes going to it

Power steering pump?

Edited 27 June, 20241 yr by huwants2no

I don't understand. 

The big fat wire from SA1 fuse does go to the alternator output. 

27 minutes ago, Breezy_Pete said:

I don't understand. 

The big fat wire from SA1 fuse does go to the alternator output. 

Sorry

I just looked again. From what I can see and those 3 pics I hope you can too the wire from SA1 comes down and then splits. One goes down to whatever is under the alternator and the other goes to Alternator itself where it also splits again...if you follow me:)

In the top pic it's the smaller cable with the white line that runs down to the other thing (I really gotta find out what that is)

Edited 27 June, 20241 yr by huwants2no

My god that's a nice clean engine (at least compared to mine!)...