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Old 05-26-2018, 02:33 PM   #1
StreetForged
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Default Did I get a dud tachometer?

I wired up an Ebay tach to my 1990 240DL last night and I couldnt get the needle to move, though the lights worked. It has a red(power?), white(light), black(ground), and green wire(Tach), which I've hooked up in the corresponding way:

-Red wire i tested on both the battery and on what i believe to be the positive post on the coil

-White is spliced onto one of the fuses on the fusebox under the steering wheel, can't remember which

-Black is grounded to a bolt on the chassis near the fuse box

-Green I have tried hooking up to both the blue wires on the coil, and the red and white wire behind the gauge cluster that I believe is for the OEM tach?

I have done some research to get this far, but at this point I'm just assuming the tach itself is a dud. I have installed two of these on other cars before and haven't had this same issue, but I could have done something wrong and figured someone else might have more of a clue than me.
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Old 05-26-2018, 07:10 PM   #2
dl242gt
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Maybe the tach uses a five volt digital signal instead of the coil switching signal like the stock tach? The white/red inside the dash comes from coil terminal 1 to provide the signal to the tach.

Red is power on your tach? It should go to a switched fuse like fuse 12 or lower.
White? Illumination? should go to one of the wires for the center console lighting.
Black to a good ground.
Green is your signal wire? Then that should connect to the white/red inside the dash. If the tach works with the coil switching signal. Like I said you may need a different tach if it doesn't use that type of signal.
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Old 05-26-2018, 07:20 PM   #3
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Which particular Ebay tach did you buy?
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Old 05-26-2018, 11:04 PM   #4
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Which particular Ebay tach did you buy?
Don't judge me lmao, I went as low budget as you could go so I shouldn't be too surprised if it is the fault of the tachometer itself.
https://www.ebay.com/itm/3-75-Univer...72.m2749.l2649
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Old 05-26-2018, 11:22 PM   #5
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Lol less than $14.99 shipped you done did good.

Good enough you can sh!t can it and not look back.
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Old 05-26-2018, 11:32 PM   #6
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Lol less than $14.99 shipped you done did good.

Good enough you can sh!t can it and not look back.
Exactly, so long as I can get one that does work lol
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Old 05-27-2018, 07:22 AM   #7
M.H. Yount
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Even if it was expecting a 5V signal, if working it would register, just way off.
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Old 05-27-2018, 05:42 PM   #8
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Originally Posted by Redwood Chair View Post
Lol less than $14.99 shipped you done did good.

Good enough you can sh!t can it and not look back.
lol that is true. I would just find a stock 240 tach if it were me.
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Old 05-27-2018, 09:24 PM   #9
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lol that is true. I would just find a stock 240 tach if it were me.
I would have done that but I couldn't find one for less than 100 bucks so I figured whatever, I'll keep the clock and spend 15% of that and get the same feature, but here we are...
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Old 05-27-2018, 09:35 PM   #10
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I would have done that but I couldn't find one for less than 100 bucks so I figured whatever, I'll keep the clock and spend 15% of that and get the same feature, but here we are...
You can get one for a lot less than that by posting in Wanted here.
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Old 05-28-2018, 04:03 AM   #11
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If you have another car, you could always test the tach on it to make sure its actually working.
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