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| Tachometer Issues (Page 1/1) |
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Mark_j
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DEC 17, 10:09 PM
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Seems that I am chasing a ghost.
88 with Duke.
Issue is kind of strange. My tach "drops out" intermittently.
Doesn't last for very long, several minutes at the most but during that time the tach is dead, then it comes back up to operate normally.
Service manual doesn't say anything specific so chasing it down is a bit of an issue.
Grounds were done when I changed the clutch several yeas ago.
No listing for tach filter (but if there is supposed to be one I'd really like some confirmation ot it).
Module and crank sensor are probably the originals.
No other issues with how the engine runs.
Everything seems to be normal except for this issue.
Ideas?[This message has been edited by Mark_j (edited 12-18-2021).]
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Gall757
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DEC 19, 10:18 AM
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WalkerTexan
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DEC 19, 10:57 AM
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I suspect a bad connection on the rear side of the tach and/or the housing.
The tach uses large pins on the back to plug into spring clips in the housing. Those clips can get weaker with time and can oxidize so that the connection is lost. Happened to mine.
Take the tach out and clean the clips with an emory board and pinch them together so they will be tighter against the pins and clean the pins with sandpaper.
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Mark_j
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DEC 21, 12:30 AM
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I was planning to take the instrument panel out this spring and re-wire for the temp gauge pegging issue so that adds another thing to check on, thanks.
BTW, I have a panel from an 85 SE in my parts collection can that be adapted to the 88?
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WalkerTexan
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DEC 21, 11:45 AM
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I haven't compared the internals from an 85 to an 88 so I don't know for sure. I think it will swap out fine since I know my 85 and 87 were compatible. I doubt any major changes were made in 88 since the VSS output is the same for the tach and odometers. All of the panel lights are the same and every year has the same mistake in the temp gauge circuit. I assume the speedo is compatible as well. I would check the schematics between 85 and 88 to make sure the wires in the panel connectors are the same, i.e. same signal on each pin. I suspect they are.
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theogre
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DEC 21, 05:15 PM
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| quote | Originally posted by Mark_j:
Seems that I am chasing a ghost.
88 with Duke.
Issue is kind of strange. My tach "drops out" intermittently.
Ideas? |
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All 85-88 4 cyl tachs are same. But Replacing the tach may not help now or fail again soon after...
87-88 Duke Does Not have the Tach Filter on the engine. That line terminates at the DIS Brick. So ignore anything pointing to a iffy/bad filter.
Drop outs like this then often problems in the Dash or Tach itself. If you bump the dash and solves/causes this problem then have to take back and front trim off even to start looking for problems.
Big plug(s) on back of dash often have problems. Worse loose copper on the "board" where they plug in. So Be careful because that can short out 1 thing or whole dash depending what trace is loose.
Tach board connect to dash back w/ SS spring clips and 1 or more gets loose as back plastic and board warps etc. Back Copper gets corroded, etc.
Tach bolts that uses the clips get dirty or loose. Tach Meter and Oil Gauge has same to connect w/ the tach board. Can take them apart and reinstall but Do Not over tighten the nuts.
Before and after doing work...
Check the clips in back of dash to see if there a bit tight.
SHOULD be that where hits the copper.
Clip load can change when whatever part is remove and be loose w/o the bolts spreading other side.
See http://www.fiero.nl/forum/Forum2/HTML/138175.html Instrument panel bulb layout
Note: If tach has problems w/ the clips and bolts... very likely has same problems w/ oil temp and fuel gauges.
All gauges have "power" resisters on them and nuts holding them. Can carefully clean connection areas but again Do Not over tighten the nuts.
These nuts only need "barely tight" just to stay put. Even using "screwdriver style" nut drivers can easily wreck the nut, break the resistor, and worse when you use your whole hand to tighten. ------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
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