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Old 09-03-2014, 02:41 PM   #1
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Tach needle bouncing

The tach needle on the dash is bouncing. The digital readout is functioning properly, thoughts??
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Old 09-03-2014, 03:01 PM   #2
Join Date: Feb 2009
Location: Goodyear, AZ
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This has come up a number of times, use the search for a detailed explanation. My guess is it only happens to you with the generator running. You can likely stop it by running with your headlights on.
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Old 09-03-2014, 03:09 PM   #3
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Thanks for your quick response, Pete.. Tried a search before I posted, unable to locate the topic... Thanks again..
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Old 09-03-2014, 03:31 PM   #4
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Location: Goodyear, AZ
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It has to do with the voltage regulator, alternator, and diesel generator handing the load back and forth. When the load is exchanged the voltage goes through zero and the tach drops to zero. I have the problem also. The correct explanation is far too complex for me to fully understand, remember, and relate. Your tach gets it's input from the alternator. Turning the lights on keeps the load from being exchanged. Try different verbs tach "jumps."
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Old 09-09-2014, 10:12 PM   #5
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Location: Westminster, SC
Posts: 34
Bouncing tach

Check the plug on the back of the alternator and make sure it is plugged in properly. They can sometimes vibrate loose.

Randy & Sheron
Upstate SC
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Old 09-14-2014, 06:39 PM   #6
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I had intermitent tack also so I called leece-neville district tech rep. He said start at the alternator checking connections and move backward. Guess what? The wire that energize the alternator had broken. Obviously it was apperating off one wire before it have no wires connected then no tack.
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Old 09-14-2014, 09:31 PM   #7
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Location: Saint-Sauveur, Quebec, Canada
Posts: 66
I experienced a similar situation.

At a cruising speed of 60 miles per hour, the tack needle would go from 1,800 to zero back to 1,800 in a split of a second. Turn out to be that the TPS, Throttle Position Sensor that was defective.
2003 Monaco Dynasty Regent 40' w/tag
2004 Jeep Grand Cherokee Ltd
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Old 01-28-2018, 04:39 PM   #8
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We had the same bouncing tach, and the water temp would read erractic and then go negative. Although I did the 300 ohm resistor on the Beede tach pins the symptoms continued, then got worse with no start on chassis but okay on boost. Turned out to be the stack of engine control ground terminals on the negative chassis battery post. They were under the main 00 chassis ground instead of on top of the giant lug. The contact area on the little ring terminals was impeding the high current required for the starter. Replaced the big terminal in contact with the lead post and then stacked the ring terminals on it, with a star washer. No problems in over 10,000 miles.
2005 Neptune 34SBD
"The Gold Coach"
2006 Saturn Vue AWD
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