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Discussion Starter · #1 ·
My tachometer is really starting to give up the ghost, I think. Riding down the highway at a constant speed, it has always had a vibrating needle, but now it has starting jumping around in 1k increments. Are any there decent, but not crazy high cost replacement options out there? I know the stock Ducati tachs have never been universally loved, so I've got to figure that someone has an option to look at?

Thank all.
 

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It could be something other than the tachometer itself. Does the engine surge slightly when it happens? It could be the TPS. Get on a long straightaway, hold the throttle very steady, and pay close attention to the engine.
 

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Pull the tach and check the brass screws on the back. They have been known to loosen. No good direct swap replacement options that I know of. If you wind up needing one, look to eBay for used OEM. They aren't particularly accurate, or particularly inaccurate either, but they are pretty reliable. Failing tachs are rare(ish) and a used OEM will serve as any other OEM that's working.
 

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On mine the screws were tight so I took it apart and found the soldered joints were broken where the connector plug is joined to the printed circuit board.
 
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Discussion Starter · #5 ·
On mine the screws were tight so I took it apart and found the soldered joints were broken where the connector plug is joined to the printed circuit board.
That's certainly something to look at this winter. Thanks!
 

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These tach units are very sensitive to electrical failures elsewhere on the bike and items going south.

Check your Regulator Rectifier connections. Check battery. Check the stator (keep in mind the stator can fail when hot and show good when cold.) Check all connections leading to the Tach. I had a bad battery as the culprit. If all seems to check out, do a proper voltage test at the battery when running at idle and then above 2500. If it is the R/R it will show at this point. Just need to set a priority list of likely items. The Tachs need proper voltage and without same, you'll see erratic read-outs.

If it is the voltage Regulator - Rectifier, get a genuine SHINDENGEN MOSFET FH020AA REGULATOR/RECTIFIER. Available on Ebay or Amazon. Yes, you'll see Mosfet junk for $20, but stay away. You get what you pay for.

BTW, the best one stop shop for RR, other electrical items and advice is https://ricksmotorsportelectrics.com/

Steve
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REGULATOR/RECTIFIER
The regulator/rectifier on your motorcycle performs two functions. The rectifier portion converts the AC power from the alternator into DC power so that it can charge the battery. The regulator ensures that the voltage is delivered within certain limits, as not to damage the battery. Excess power is converted into heat by the regulator to get rid of it. The regulator and rectifier are often together in one unit, but for some bikes (mostly older), they can be separate.

To test the rectifier, you will need to disconnect all of the wires and turn your multimeter to the diode function. First, check the positive diode. To do this, place the positive lead into the positive diode. Then connect the negative lead to each of the stator inputs. The meter should not read anything on any of these. If that checks out, connect the negative lead to the positive diode and connect the positive lead to each of the stator inputs. The meter should now be reading something. The numbers are not important.

Motorcycle Regulator Rectifier
Repeat the process for the negative diode. This time you should get a reading with the positive lead connected to the negative diode while connecting the negative lead to the stator inputs. With the negative lead connected to the negative diode, the meter should not read anything while connecting the positive lead to the stator inputs.

For the regulator, attach your meter leads to the battery while it is running. It should not read higher than 14.5 volts and no lower than 13.5 volts. If it is higher, the battery will be over charged and if it is lower, the battery will continue to drain as the bike runs.

If these tests do not check out, you will need a new regulator/rectifier.
 
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