Tach gone crazy
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Posting Guru
Joined: Jun 2004
Posts: 1,808
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From: Cincinnati Ohio
Tach gone crazy
When driving down the road my tach is starting to bounce around, and when at idle it goes to 0. When I got home last night and parked the truck and looked at the tach it read the normal 700RPM, what could be making the tach read wrong and bounce?
Lead Driver
Joined: Mar 2006
Posts: 5,111
Likes: 1,549
From: western SD
My first guess would be the tach sensor on the engine. Check to see if the wires coming out of the nut are bare. On my 85 the gauge itself went bad, and I had to reolace it with the tach from my parts truck.
Postmaster
Joined: Apr 2008
Posts: 4,802
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Must be nice not having an E4OD now, ain't it? If you did those tach issues would have mede for a very interesting trip home. But yeah, like Farmert said, check your tachometer sender on top of the IP gear housing, insulation on wires shrinks with heat from hours and hours of engine running and the wires go bare, sometimes enough to touch each other and short, causing all sorts of havoc at the tach.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
imboostedru,
Welcome to FTE and the IDI diesel forum.
I am going to second the ground problem.
There is a lot of metal under the dash that is not grounded.
Same under the hood.
Start checking ground straps and wires, headlights, body to engine, body to frame (both front and rear) and under the dash.
Welcome to FTE and the IDI diesel forum.
I am going to second the ground problem.
There is a lot of metal under the dash that is not grounded.
Same under the hood.
Start checking ground straps and wires, headlights, body to engine, body to frame (both front and rear) and under the dash.
Freshman User
Joined: Oct 2008
Posts: 27
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Thanks for the tips. I will check them as soon as I can get off work before dark and if it ever stops raining here(WA). Where are the grounds under the dash?
Shawn
Shawn
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Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
I would say loose contact. Either a ground or some other connection. Bouncing from normal down to zero and back means total power loss for brief moments when the power is cut. If there was an internal problem with the tach or the sender, I would expect a more stable but lower signal.
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