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740 Please help me fix my dashboard

rwb

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Aug 15, 2017
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740
1990 740 GL (Regina, though I don't think that matters here.) Race car so electrical system stripped to basic functions.

I cut a lot of wires to the dashboard, since I didn't think I would use it. Unsurprisingly, it doesn't work when I plug in what's left.

The ONLY things I need working are temp sensor and gas gauge, tach would be nice but not necessary.

I am wondering what I need to reconnect to get those gauges working. The wires for those functions are OK, but I get no life at all from the gauges.

Looking at the diagram below, am I correct in reading that all three of my favorite gauges get 12v from the connection to the high-beam indicator light? So if I get 12v to A8, and B4/B7 (for temp,) C6/B1 (fuel,) and the tach cables, should I expect those to work, or am I missing something?

Unfortunately I discarded the 8-pin A block when I was cutting things, so I will be posting to wanted for that if this thread returns results.

MA7ESxA.png
 
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I didn't pay anything for this one so you'd better have a great deal.

Anyway yeah I know ha ha bolbo seben farty is 4 homless, but I was hoping this would be more productive before it hit the "this thread sucks" stage.
 
If you really are asking about a 740, then I think you may have the wrong schematic, but without specifying the year and trim (i.e. Turbo, GLE, etc.) there is not much that can be told.

BTW, on some models, the instrument cluster board actually helps regulate the 12v for some of the devices in the car.
 
Edit: OK, I think I figured out the wiring. Try this:

1) +12v to cluster: pin D4
2) ground to cluster: pin D3
3) Speedo VR sensor wires (two) to cluster: pins D1, D2 (doesn't matter which wire to which pin)
4) Red-White wire to back of tach -- you'll need to find a greenbook with a drawing of your tach model
5) Coolant temp sensor wires (two) to cluster: pins B4, B7 (doesn't matter which wire to which pin)
 
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Thank you bobxyz for taking a look. One thing I was confused about is "conn #31 (fuse block)" so that's just a spade on that row of hot terminals? Those have no numbers and there are only 26 fuses so still fuzzy there.

Also, does anyone besides Dave Barton sell little connectors like this? I checked there and didn't see anything, and will only bother the wanted section if there are no new ones. It sounds like I need the 4 pin d block in addition to the a.
 
Thank you bobxyz for taking a look. One thing I was confused about is "conn #31 (fuse block)" so that's just a spade on that row of hot terminals?
Look closer at your fuse box diagram. CONN #31 (--)
The "minus" means it's a bunch of grounds, not powered.
As stated, if you have power at D4, and ground at D3 (and / or C11), most things should work, as long as they're hooked up to their sensors.
 
Ah! I guess I could have checked the diagram to see what that meant instead of staring at the fuse box like a monkey. Also mixed up D3/D4 which could have told me.

Anyway, I will maybe see if I can tape a pin to D4 at least to try it out, I have C11 connected but will find out if that's enough. Ideally I will find a connector I can put the pins into.

Thank you all for your help!
 
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