 tach testing, two bad tachs? |
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| Alphaogre |
 May 30 2015, 05:27 PM
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#1
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Member  Group: Members Posts: 460 Joined: 28-May 12 From: San Diego Member No.: 14,487 Region Association: Southern California  |
I am in the process of trying to get my tach working. I baught a used one under the assumption that mine had an internal issue. The second used one I picked up also is not working when I hooked it all up.
I read on an old pelican forum that you can test the tach by connecting it outside of the wiering harness by connecting the + to Power the - to ground and the blk/purple plug directly to the - on the coil. Would this infact work? What if you dont have the original coil, but a replacement one? would that matter? I connected the + of the tach to the + on the batt, then the - of the tach to the - on the batt. I then connected the blk/purple connector directly to the - on the coil. Am I doing somethint wrong here? Are these VDO Tach known for going out? Any help would be great! This is all on a 1970 914 4 1.7 |
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| Spoke |
May 30 2015, 06:31 PM
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#2
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Jerry Group: Members Posts: 6,978 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None 
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Connecting blk/purple to NEG on the coil is how it is connected in the car. By doing this test you are taking the wiring out of the equation. Good way to test the tach. I doubt both tachs are bad. You may have a wiring issue.
When was the last time your tach was working? |
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| 72wrxporsche914 |
May 30 2015, 11:38 PM
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#3
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Member Group: Members Posts: 52 Joined: 3-May 15 From: Fresno ca Member No.: 18,697 Region Association: None |
The tack also needs 12 volts . Check your power with the key on .
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| Alphaogre |
May 30 2015, 11:50 PM
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#4
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Member Group: Members Posts: 460 Joined: 28-May 12 From: San Diego Member No.: 14,487 Region Association: Southern California |
I checked it while it was running and the tach was getting 12V. Still perplexed... (IMG:style_emoticons/default/confused24.gif)
The tach stopped working right as I bought the car, right before I stripped and restored it. That's why I wanted to see if they would work directly powered. It is also why I bought the second tach, I assumed that the original had internal issues but never really tried to chase down the issei until today. I wanted to test the tach's to be sure they were working before I go chasing wires all over the car. |
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| 72914wrx |
May 31 2015, 12:29 AM
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#5
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Member Group: Members Posts: 86 Joined: 5-January 15 From: Fresno Member No.: 18,298 Region Association: None
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Use a volt meter and Omh it out the wire form the tack to coil . Should be at 0.2 to 0.3 .
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| timothy_nd28 |
May 31 2015, 07:52 AM
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#6
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Advanced Member Group: Members Posts: 2,299 Joined: 25-September 07 From: IN Member No.: 8,154 Region Association: Upper MidWest
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Send them to me, I'll test both of them for free.
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