Solved: Alternator Wiring Testing

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lewiswhitmore524
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Solved: Alternator Wiring Testing

Post by lewiswhitmore524 » 09/06/19 15:06

Hey all.

I've been having some long standing issues with ignition and battery drain on my rev2 turbo. Up to now, I've always had the expected charge voltage of around 14v at the battery terminals when engine is running.

I was about to take it out the other day when the window wipers were going slower than I'd expect. Turns out I'm no longer getting charge voltage at the battery.

I found a few posts about this issue previously and have tested the alternator plug voltage with ignition on. I get battery voltage at both of the outer pins, but only 2.5v on the middle pin. This is the black wire with the yellow stripe.

Where does this wire get its supply from? Looking to try and trace down the issue. I'm assuming in the engine bay fuse box, but after some probing i cant find continuity between any of the plug pins and the alternator middle pin. What does the middle pin do? And where is the source of 12v prior to the engine bay fuse box?

Thanks all.
Last edited by lewiswhitmore524 on 18/06/19 21:18, edited 1 time in total.



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abovetherim
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Re: Alternator Wiring Testing

Post by abovetherim » 09/06/19 15:47

Hey dude
Yes the black/yellow goes to the engine bay fuse box.
From there I assume it goes to the ECU.
Later when I get time I'll have a look at a wiring diagram.

But there was a recent post with a link to testing the various points of the charging circuit..... But my first point of call would be to run a temp fresh cable from the fuse box to the alt spliced into the BLK/yellow at either end.

I believe there are fuses in the kick panel box that affect the charging circuit.
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Re: Alternator Wiring Testing

Post by lewiswhitmore524 » 09/06/19 16:57

Im just confused as to why it'd be 2.5v and stable. I would expect either 12v or nothing if it was fuse related.

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Re: Alternator Wiring Testing

Post by jimi » 09/06/19 17:31

Black is not a colour ! .... Its the absence of colour
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Re: Alternator Wiring Testing

Post by lewiswhitmore524 » 09/06/19 17:44

I've checked these. Thanks :) . I'm aware that its a wiring issue I'm just wondering about the how of tracing the issue now. The fuses are all fine.


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Re: Alternator Wiring Testing

Post by MRHAPPY62 » 09/06/19 18:43

abovetherim wrote:
09/06/19 15:47
Hey dude
Yes the black/yellow goes to the engine bay fuse box.

But there was a recent post with a link to testing the various points of the charging circuit..... But my first point of call would be to run a temp fresh cable from the fuse box to the alt spliced into the BLK/yellow at either end.
first thing to do :th:
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Re: Alternator Wiring Testing

Post by lewiswhitmore524 » 09/06/19 18:53

MRHAPPY62 wrote:
09/06/19 18:43
abovetherim wrote:
09/06/19 15:47
Hey dude
Yes the black/yellow goes to the engine bay fuse box.

But there was a recent post with a link to testing the various points of the charging circuit..... But my first point of call would be to run a temp fresh cable from the fuse box to the alt spliced into the BLK/yellow at either end.
first thing to do :th:
Ill try this. Im still not sure which pin on the connector it is but I'll consult the BGB.

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Re: Alternator Wiring Testing

Post by jimi » 09/06/19 20:02

Black/yellow goes to the 7.5A fuse ECU-IG. Also passes through connector EB1 (below the fuse box I think). If you take out the fuse and test the fuse sockets, one side should have battery voltage, the other 0v. With your meter set to ohms test from the 0v socket to the appropriate pin on the alternator plug, should get a low (0.1ohms or thereabouts) if not try to trace the wire to the EB1 connector and repeat the tests from the fuse to the connector pin and from the connector pin to the alt plug, that should narrow down where the problem is, could be a slack/corroded connector of a wire damaged or broken internally, if that's the case replace the wire.
A quick check would be as suggested, a temporary wire from the fuse to the appropriate pin on the alternator plug.
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Re: Alternator Wiring Testing

Post by lewiswhitmore524 » 09/06/19 21:59

OK,

So getting high resistance between the fuse socket and the alternator pin.

Furthermore, i've manged to determine that the body side pin of the EB1 connector is getting the appropriate 12V when ignition is on. Must be the wire between the engine side pin of EB1 and the alternator plug.

Is this a direct cable that goes to the plug or does it go somewhere else first? I'll rig up a temp wire tomorrow and see if that fixes my issue. I'd like to fix it properly however. Is the cable run relatively straightforward if i wanted to remove the wire and do it properly? I'm thinking if one wire has had a problem, others in the loom may have also.

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Re: Alternator Wiring Testing

Post by jimi » 09/06/19 22:08

That's good progress :th:
According to the diagrams it's direct from EB1 to the plug, IIRC it runs in a plastic conduit either under or above the inlet manifold, its been known for that wire to fail in that area. I've repaired a couple like that in the past (must have been 5/6 years ago so can't remember exactly how I replaced the wire :blush: )
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Re: Alternator Wiring Testing

Post by lewiswhitmore524 » 12/06/19 11:52

OK so, Wiring harness removed.

Image

First and foremost, i have found the issue, and it's with one of the splices in the loom which after consulting with Dawesey are factory splices (thanks!). I was significantly less irritated with the previous owners once i found out these splices are put in by Toyota. The insulation on these joints is basically just tape though which surprised me, so I'm keen to improve on this by doing it with some proper heat shrink. I will also re-do the other crimps which are currently in good condition, just to future proof so I don't need to have the loom off again in the near future.

The bad joint

Image

One of the good joints which I'll insulate more robustly.

Image

I have a few questions though along the way. What is this thing? It was just flapping in the breeze dangling in the engine bay. Where does it mount?

Image
Image

Secondly, this sensor here:

https://imgur.com/n1nZH8W

Im assuming this is the oil pressure switch. Is there any notable upgrade that can be done here or is standard OEM part the best? Does it just control the light on the dash?

Thanks all :) on the mend now, should be done in time for any shows, and more importantly, should be sorted for when i move house at the end of the month!

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Re: Alternator Wiring Testing

Post by SonicSW20 » 12/06/19 12:43

Thing by the distributor is a noise filter. IIRC, it mounts to one of the bolts on the rear firewall. Don't think it really matters which one, just find one it reaches comfortably.

And yes, thats the oil pressure switch. Makes the idiot light come on. If that light does come on though it's already too late most of the time!
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Re: Alternator Wiring Testing

Post by jimi » 12/06/19 18:46

Great pictures, if you don't mind I could add them to the KY2 article ? where about in the harness (in relation to the engine) are the splices located ?
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Re: Alternator Wiring Testing

Post by benckj » 12/06/19 19:43

Good find, might just check mine to see if ok and insulate better. Where exactly is the join located?

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