Farm Equipment - Allis Chalmers 7020 Tachometer Not working

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Allis Chalmers 7020 Tachometer Not working

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=139345
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Topic: Allis Chalmers 7020 Tachometer Not working

Posted By: Basehorhawk
Subject: Allis Chalmers 7020 Tachometer Not working
Date 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?

Replies:

Posted By: Mrgoodwrench
Date Posted: 12 Jun 2017 at 8:27am

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.

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Posted By: Basehorhawk
Date Posted: 12 Jun 2017 at 8:39am

I will. Thank you very much.

This Forum is priceless.

Posted By: MACK
Date Posted: 12 Jun 2017 at 10:11pm

Tighten fan belts. Belts are slipping. MACK

Posted By: Basehorhawk
Date 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.

Posted By: charlesbendal
Date Posted: 15 Jun 2017 at 6:14am

Did you just visually inspect the wiring or did you clean the connections?

Posted By: DougS
Date 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.

Posted By: Basehorhawk
Date Posted: 15 Jun 2017 at 9:57am

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.

Posted By: DougS
Date Posted: 15 Jun 2017 at 10:17am

Okay. Did you change the alternator recently?

Posted By: Basehorhawk
Date Posted: 15 Jun 2017 at 10:49am

Nosir. It's not original to the tractor but was on it when I bought it.