Electrical issue after alt belt change: wiring diagram and question about specific circuit

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Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 11/01/18 12:23

Hi guys,

Full back history in thread called "MK2 internal fan/heater completely dead", but quick summary: Car in for alt belt change. Alt fuse blew during work. Replaced. Internal fan/heater, all dashboard dials/gauges and power steering dead. Garage claims electrical issues caused by pre-existing fault behind radio (chafed wire that had touched metal), not their alternator work. Advised by you guys and talked to auto-electrician who garage told me had diagnosed the problem. Auto-electrician confirmed he'd only isolated circuit after taking dash apart, not diagnosed anything. Notably, he was NOT briefed that alt fuse had previously blown (only told to look for battery drain). He agreed with you that alt work likely to be involved, as blowing 120A fuse hard to do.

I have 2 questions now, please, to help this sparks get to the bottom of this, please:

1. Issue has been isolated to one circuit: junction box 3 (behind instrument cluster), connection 3D, pin no. 2. When he removes this wire, the fault goes away (at least the fan and dials work). He needs to trace back along this wire to see what's on that circuit. Million dollar question: is the alternator on this circuit??? Is the power steering on this circuit too?

2. Does someone have a wiring diagram for my car they could share, please? It's a mark 2 MR2 2.0 GT 16v manufactured and registered in 1999.

I'm only at this point because of advice you guys have given me. I was looking at writing off my lovely car. THANK YOU!

Jo



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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by MR2Jay » 11/01/18 15:30

Wow, that's a pretty spectacular fault but one that it looks like you are narrowing down :th:

I haven't got them with me but try and find a copy of the BGB (Big Green Book) online. There are several PDF versions floating about - I think Shinny deposited them somewhere people can download them.

If I get chance, I'll have a look at my copy at home and see if I can work out what that junction box does :th:

**edit** - Found the links :th: http://www.mr2oc.co.uk/forums/198/80372.html
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jimi » 11/01/18 17:07

1999 would be a Rev5, you'll struggle to find Rev5 diagrams, I've never seen any, best you'll gett is the 1995 diagrams which you can download from here
http://www.mr2oc.co.uk/download-cats/do ... agram.html
They should be close with possibly some minor differences but in my experience the major circuits are pretty much the same.
Be aware that these diagrams are for the Turbo (3S-GTE) and the 5S-FE (USA only) the only specific N/A diagrams I know of are these http://www.mr2oc.co.uk/download-cats/do ... grams.html which may be to old. I'd download both and give them to the sparky, hopefully they will at least guide him in the correct direction.
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 11/01/18 21:22

Thanks, guys! I am soooo hoping the circuit he's isolated is connected to the alternator. I will pass on all you've suggested.


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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 13/01/18 9:27

Any thoughts at all about what might be on that circuit, or how difficult it'll be to determine that? I'm presuming difficult as the fault he's found behind the radio is in the dash and the alternator isn't exactly nearby....
Stupid question, but he hasn't even looked at the alternator yet (garage never mentioned alt fuse had blown), so if there was a big short by the alternator when they changed the belt, would it show? Blackening or whatever? Just wondering how big a job it is for the guy to link this back to the alternator, assuming (has to be likely) that it's where this all started.
Have a lovely weekend.
Jo

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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jimi » 13/01/18 21:19

I can understand why he's not looking at the alternator, (apart from not being told about the Alt fuse blowing) since the fuse has been replaced and hasn't blown again then whatever fault caused it to blow isn't there now, so not much point in looking there.
He's trying to trace the fault that is causing the 7.5A fuse to blow, hopefully once that is sorted you will be good to go.
It might be worth him checking R/B 5 (fuse box in the front boot that contains the 120A Alt fuse) as the 120A alternator fuse is bolted into that fusebox from below, replacing it involves partially dismantling the box to get to the underneath and it's possible they have done something wrong while changing that fuse.
This article shows how to change a main fuse ( with pictures) http://www.mr2oc.co.uk/know-your-2/mk2. ... bartid=283
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 13/01/18 22:56

Thank you very much, Jimi. That's very helpful, as usual.
I'll tell him that for sure.
Enjoy the rest of your weekend.
Jo

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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jimi » 13/01/18 23:58

jo_martin64 wrote:
11/01/18 12:23
Issue has been isolated to one circuit: junction box 3 (behind instrument cluster), connection 3D, pin no. 2. When he removes this wire, the fault goes away (at least the fan and dials work). He needs to trace back along this wire to see what's on that circuit. Million dollar question: is the alternator on this circuit??? Is the power steering on this circuit too?
What's the colour code on that wire ? If I know that I can have a look at the diagrams I have.
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 14/01/18 13:45

Cheers, Jimi. I will ask him.
Jo


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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 14/01/18 14:28

Hi Jimi,
I checked with him and he says it is the R-L one on the attached picture and it's red and lilac.
Any light you can shed would be awesome.
Thank you!!!!
Jo
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jimi » 14/01/18 18:31

R-L is Red and Blue, Toyota don't use Lilac, they do use Violet but the code for that is V (page 5 of the electrical diagrams pdf has a list of the colour codes.
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jimi » 14/01/18 18:57

Bit of confusion going on somewhere, 3D pin 2 isn't R-L according to the diagram you posted.
Look at the bottom section [J/B No3 Inner Circuit]
look down the left hand side and you'll see 3D-2 is connected to the R (Red ) circuit which is fed from the 15A Dome fuse.
Further down you'll see the R-L circuit and a list of the Plug/pins connected to it, the R-L circuit is fed from the 7.5A Gauge fuse
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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by jo_martin64 » 14/01/18 21:55

Thanks, Jimi. I will check with him.


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Re: Electrical issue after alt belt change: wiring diagram and question about specific circuit

Post by MRHAPPY62 » 18/01/18 20:27

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