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Basehorhawk 
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Joined: 10 Jun 2017
Location: Basehor Kansas
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 Topic: Allis Chalmers 7020 Tachometer Not working
Posted: 12 Jun 2017 at 8:21am |
Hello all, on top of my PTO issues with my tractor (1978 Allis Chalmers 7020, around 5700 hours), my tachometer quit showing me RPM's. Will only show around 500-750 even when i'm up around 2500 or so.
Any idea's or questions I can answer that may help you all diagnose?
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Mrgoodwrench
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Joined: 03 Apr 2011
Location: CHICORA PA
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Posted: 12 Jun 2017 at 8:27am |
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Check the wires at your alternator. That tach is run by the alternator . Ours has a delco on it and the third wire is for the tach.
Edited by Mrgoodwrench - 12 Jun 2017 at 2:43pm
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There are 3 ways to do job GOOD, FAST, CHEAP. YOU MAY CHOOSE 2. If its FAST & CHEAP it won't be GOOD, if it's GOOD & CHEAP it won't be FAST, and if its GOOD & FAST it won't be CHEAP!!!!
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Basehorhawk
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Location: Basehor Kansas
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Posted: 12 Jun 2017 at 8:39am |
I will. Thank you very much.
This Forum is priceless.
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MACK
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Posted: 12 Jun 2017 at 10:11pm |
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Tighten fan belts. Belts are slipping. MACK
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Basehorhawk
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Posted: 14 Jun 2017 at 3:33pm |
Tightened up the belts. Had a little squeal at times before I snugged them up, which that resolved, but the Tach still will only go up to around 500 RPM. Looked at the wiring and everything looked ok.
Any other suggestions? Could this possibly be related to my PTO issues i'm having from the 7020 PTO/Diff lock problems thread?
Running out of ideas on the old gal.
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charlesbendal
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Posted: 15 Jun 2017 at 6:14am |
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Did you just visually inspect the wiring or did you clean the connections?
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DougS
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Location: Iowa
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Posted: 15 Jun 2017 at 6:36am |
Considering that the tach needle never moves I'd discount the problem as being a loose belt. It could be a loose wire, but I'm inclined to think the problem is the tach itself.
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Basehorhawk
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Posted: 15 Jun 2017 at 9:57am |
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To clarify, it will move up to about 500 RPM when I throttle up but I know I'm getting to around 2500 RPM, tach just doesn't climb that high.
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DougS
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Posted: 15 Jun 2017 at 10:17am |
Okay. Did you change the alternator recently?
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Basehorhawk
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Posted: 15 Jun 2017 at 10:49am |
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Nosir. It's not original to the tractor but was on it when I bought it.
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