| Dead 1 |
Mon Jun 16, 2008 10:22 am |
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What could be the cause of a brand new tach reading low? The tach never gets up or 2,000 rpms. I hade the dip switchs in the 4 cyl. position, when I change the dip switchs the tack gets worse.
Thanks. |
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| Dale M. |
Mon Jun 16, 2008 10:29 am |
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Contact VDO tech support yet?
Do you have "sense" lead on (-) terminal on coil?
Dale |
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| conrad1468 |
Mon Jun 16, 2008 12:46 pm |
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it sounds like a bad tach.. if it's set on 4cyl it should work right..
i have tachs on elec and mech points and it reads good...
just was long as you have the green wire (tach wire) on the neg side of the coil it should work.. |
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| Dead 1 |
Mon Jun 16, 2008 12:51 pm |
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conrad1468 wrote: it sounds like a bad tach.. if it's set on 4cyl it should work right..
i have tachs on elec and mech points and it reads good...
just was long as you have the green wire (tach wire) on the neg side of the coil it should work..
The tach is connected to the - side of the coil. Could a bad ground cause low readings? |
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| Randy in Maine |
Mon Jun 16, 2008 1:45 pm |
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Low voltage might , but usually the little dipswitches are set incorrectly.
Been here?
http://www.egauges.com/Inst_PDF.asp#Tachometer
Read the part about installing a diode to prevent stray voltage also. I put mine right at the coil and it works well. |
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| Dead 1 |
Mon Jun 16, 2008 2:07 pm |
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Randy in Maine wrote: Low voltage might , but usually the little dipswitches are set incorrectly.
Been here?
http://www.egauges.com/Inst_PDF.asp#Tachometer
Read the part about installing a diode to prevent stray voltage also. I put mine right at the coil and it works well.
How would you have low voltage at the coil? |
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| Randy in Maine |
Mon Jun 16, 2008 3:42 pm |
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I was thinking a poor ground and wrote "low voltage". I think mine grounded at the dash. My bad.
I still like incorrectly set dip switches though. |
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| Dead 1 |
Mon Jun 16, 2008 4:21 pm |
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| Im getting 9.3 volts at the coil with the key on but engine off. Could this be the cause of the tach issue? Why would there be only 9.3 volts and 12.6 at the battery? |
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| Dale M. |
Mon Jun 16, 2008 4:37 pm |
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Dead 1 wrote: Im getting 9.3 volts at the coil with the key on but engine off. Could this be the cause of the tach issue? Why would there be only 9.3 volts and 12.6 at the battery?
Probably not relevant, tach senses transition from voltage to ground when points open and close or electronic module switches "ground" on/off...
Check voltage at supply to tach, check quality of ground connection supplying ground to tach....
Dale |
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| Bugorsh |
Mon Jun 16, 2008 5:36 pm |
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| Either way, you should still be getting 12.6v at the coil, you need to find out where that resistance problem is. Check for bad connections, bad wiring etc. |
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| markhuebbe |
Mon Jun 16, 2008 6:19 pm |
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| Do you have a diode on it? I know mine needed one to work properly. |
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| Dead 1 |
Mon Jun 16, 2008 6:22 pm |
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| Yeah I have a diode on it :( |
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| Dead 1 |
Tue Jun 17, 2008 7:57 pm |
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Check this wire out. This is the fuse to coil wire. You think this might have something to do with the tach?
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| Dale M. |
Tue Jun 17, 2008 8:06 pm |
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As far as I know wire to coil IS NOT a fuseable link..... If wire is nicked or almost cut through, yah, it might be a problem...
If its burned, it's because at some point it was probably "shorted" to ground and it is not a fused lead. It is powered "directly" from battery through ign. sw.
Where is wire from (-) side of coil to tach, is it in that bundle?
What model is tach, and is diode installed correctly.... I can't seem to find anyplace on VDO tech site where it requires diode....
Dale |
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| Dead 1 |
Tue Jun 17, 2008 8:36 pm |
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Dale M. wrote: As far as I know wire to coil IS NOT a fuseable link..... If wire is nicked or almost cut through, yah, it might be a problem...
If its burned, it's because at some point it was probably "shorted" to ground and it is not a fused lead. It is powered "directly" from battery through ign. sw.
Where is wire from (-) side of coil to tach, is it in that bundle?
What model is tach, and is diode installed correctly.... I can't seem to find anyplace on VDO tech site where it requires diode....
Dale
Its the bare wire. In the pic its brown next to the green wire. |
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| conrad1468 |
Wed Jun 18, 2008 4:03 am |
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the brown wire is most likely a ground wire, but check the wiring diagram. which should be found on thesamba.
my coil wire melted the whole way from the engine to the trunk. i ran a new wire from the fuse box to the coil. you might want to change yours. i think i used 16 ga wire.
good luck.. |
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| Dead 1 |
Wed Jun 18, 2008 7:38 am |
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conrad1468 wrote: the brown wire is most likely a ground wire, but check the wiring diagram. which should be found on thesamba.
my coil wire melted the whole way from the engine to the trunk. i ran a new wire from the fuse box to the coil. you might want to change yours. i think i used 16 ga wire.
good luck..
The brown you see is the wire to the coil. The plastic covering is gone exposing brown slightly rusted wire. It is not a ground, the wire covering WAS black. |
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| Dale M. |
Wed Jun 18, 2008 10:40 am |
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Its actually charred copper, not rust....
Dale |
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| Dead 1 |
Wed Jun 18, 2008 11:17 am |
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Dale M. wrote: Its actually charred copper, not rust....
Dale
Thanks for the correction. 8) |
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