Alternator wiring

JOESEAT

Active Member
Jan 3, 2019
9
0
Hi, got a alternator fitted by the garage due to battery not charging.
I am having problems with the battery draining empty overnight since the alternator was fitted a couple of weeks ago. Was going to check for a parasitic drain coming from somewhere but before I do I wanted to make sure the wiring was correct in the newly installed alternator.
There are two wires coming from the car loom that go to a plug on the alternator. One wire is red and one is blue. The red wire is connected straight through but the blue wire looks like it has been cut from the loom side, and a new wire has been installed in its place from the chassis on the alternator itself. I have attached on a couple of pictures of it that will explain it better.
 

Attachments

  • img1.jpg
    img1.jpg
    1.1 MB · Views: 481
  • img2.jpg
    img2.jpg
    1.2 MB · Views: 594

RUM4MO

Active Member
Jun 4, 2008
7,784
983
South Scotland
It could be that your question is a bit tricky, I'd always only fit the correct alternator for that car, what cheap skate sort of place did that for you? Take it back to them if it was okay before and is now not okay, thinking/guessing between the lines, there should be 2 wires connecting to that plug, one is for initial field excitation and the other is to control charge demand by sensing the load. Are you sure that the "moved/fudged" bit of wiring is not just being connected to the rectifier bridge and not alternator chassis?
 

JOESEAT

Active Member
Jan 3, 2019
9
0
It could be that your question is a bit tricky, I'd always only fit the correct alternator for that car, what cheap skate sort of place did that for you? Take it back to them if it was okay before and is now not okay, thinking/guessing between the lines, there should be 2 wires connecting to that plug, one is for initial field excitation and the other is to control charge demand by sensing the load. Are you sure that the "moved/fudged" bit of wiring is not just being connected to the rectifier bridge and not alternator chassis?
Thanks for the reply, on further inspection the blue wire "fudged wire" is connected to the main 12v supply on the alternator from the battery? I think what's happened is the exciter wire has snapped somewhere further back and they have used the fudge to give it a 12v signal. When I remove the fudged wire the alternator no longer kicks in, however on removal of this wire I no longer have the parasitic drain of 0.5 amps that I was getting, has dropped back down to 0-10ma. I reckon I will need to try and find where the exciter wire goes to (fuse box, then dash?) and then either run a new wire or fix the break. Took car back to the garage yesterday and they said they couldn't fix it and would need to get an auto electrician in to do it. Do you know where I can get the wiring diagram for this?
 

RUM4MO

Active Member
Jun 4, 2008
7,784
983
South Scotland
Fair enough, I'd think that the exciter wire should come from an ignition switched point and not directly to the battery, so that would sort that out.

Wiring diagrams, best place would be Erwin as it has all the official documentation for non VW Group workshops and DIYers, failing that a Haynes repair manual should give you what you need, now I don't know if there was ever one for this 6L version of Ibiza, but the one for the similar 9N Polo might work for you - logically all the Fabias/Polos/Ibizas based on this version should all have some similar wiring at these common areas.

Edit:- one thing you could try mean time is, isolate that wire from the alternator and after starting the engine increase the engine revs a bit to a fast idle, it has been said that the alternator will "self excite" at higher revs and then keep providing a charge until you switch off, then repeat the initial fast idle to kick it into life each time after starting it until you get this sorted out.

Maybe post back and say if this does or does not work for benefit of others in the future.
 

JOESEAT

Active Member
Jan 3, 2019
9
0
Fair enough, I'd think that the exciter wire should come from an ignition switched point and not directly to the battery, so that would sort that out.

Wiring diagrams, best place would be Erwin as it has all the official documentation for non VW Group workshops and DIYers, failing that a Haynes repair manual should give you what you need, now I don't know if there was ever one for this 6L version of Ibiza, but the one for the similar 9N Polo might work for you - logically all the Fabias/Polos/Ibizas based on this version should all have some similar wiring at these common areas.

Edit:- one thing you could try mean time is, isolate that wire from the alternator and after starting the engine increase the engine revs a bit to a fast idle, it has been said that the alternator will "self excite" at higher revs and then keep providing a charge until you switch off, then repeat the initial fast idle to kick it into life each time after starting it until you get this sorted out.

Maybe post back and say if this does or does not work for benefit of others in the future.

Just gave that a try there but it didnt work. The alternator wont self excite at any revs.
I have spotted a brek in the blue wire just before it goes into a connector bolted on the outside of the starter. Looks a nightmare to get to though.
 

RUM4MO

Active Member
Jun 4, 2008
7,784
983
South Scotland
It might be that one or both leads are broken where there is a plug and socket round about the join of the engine to the gearbox under the car. Why did you get the alternator replaced in the fist case, was it because the charge warning light was never coming on or always on? If so, who ever replaced the alternator did not know too much about these cars as they should have checked for broken wires first before just fitting another alternator.

Edit:- which engine does this car have, if it is a TDI then I'd reckon that broken wires are a typical fault at this age.
 
  • Like
Reactions: JOESEAT

JOESEAT

Active Member
Jan 3, 2019
9
0
garage has ob
It might be that one or both leads are broken where there is a plug and socket round about the join of the engine to the gearbox under the car. Why did you get the alternator replaced in the fist case, was it because the charge warning light was never coming on or always on? If so, who ever replaced the alternator did not know too much about these cars as they should have checked for broken wires first before just fitting another alternator.

Edit:- which engine does this car have, if it is a TDI then I'd reckon that broken wires are a typical fault at this age.
Its 1 1.9 tdi.
The exterior lights went dim and the power steering went off when the wife was driving the car. When she got it home i checked the battery using a volt meter and was only reading aprox 11v. I checked it when car was idling and full revs but it made no difference was still reading 11v. I took the car to local garage and told them to check out the alternator charging circuit. They phoned me back next day to say the alternator was dead and i required a new one.
The battery light never came on in the car at any time.
In hindsight it looks like the alternator was probably ok and the fault was the snapped exciter wire all along. Looks like the garage has fitted a new alternator and got the same problem so then done the fudge using the 12v from the alternator power as an exciter. Which in turn is causing the parasatic drain now.
 

RUM4MO

Active Member
Jun 4, 2008
7,784
983
South Scotland
Ah, a TDI engined one, the vibration does tend to destroy the 2 wires that I mentioned due to the engine moving around so much.

Just to recap, when you turn on the "ignition" key the first stage, the charge warning light must come on, when you start the car the charge warning light must go off - if you are saying that that car did not behave like that then my diagnosis is spot on - and you should either find a garage that can fix cars or that garage to sort your car properly after you let them know what they should already know.
 
  • Like
Reactions: JOESEAT

JOESEAT

Active Member
Jan 3, 2019
9
0
Got it fixed !.
I removed the engine undertray to get to the broken blue wire.. Only had about a half inch of wire left exposed on the loom so was a bit tricky. Managed to strip back insulation to copper and fitted a wago connector and ran a new piece of wire straight into the exciter connector on the alternator connector ( after removing the fudged 12 alternator supply) battery light came on and went off on dash and alternator ran at 14v.
Checked battery for parasitic drain and back down to normal 10ma .
A result !!!
Thanks for the help RUM4MO
 
Nimbus hosting - Based solely in the UK.