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Recent Tachometer woes by triads
Started on: 02-18-2015 07:54 PM
Replies: 3 (95 views)
Last post by: peterh on 02-19-2015 08:19 AM
triads
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Report this Post02-18-2015 07:54 PM Click Here to See the Profile for triadsClick Here to Email triadsSend a Private Message to triadsEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have an 85 GT with 120 speedo and matching tach.. Everything worked fine till a few days ago then the Tach stopped functioning properly. The tach will show almost 1k more then the engine is running, so Idle at 1k shows almost 2k on the tack. Revving the engine shoots the needle passed redline.. I took the filter out of line and didn't change anything. Before I go blindly digging into wiring and such, I'm hoping someone here may have had the same issue with a fix or can offer some places too look first. All other gauges work, speedo has a little bounce but that's for another time..

If there was a topic discussing this issue, I apologize for the dupe post.. I just didn't see it...

Thanks for looking..
J
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triads
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Report this Post02-18-2015 08:59 PM Click Here to See the Profile for triadsClick Here to Email triadsSend a Private Message to triadsEdit/Delete MessageReply w/QuoteDirect Link to This Post
After some pff searching, i'll look at my icm & p/u coil first...
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Csjag
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Report this Post02-19-2015 07:42 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Google "GM tach reading too high" there is a helpful thread that tells how to replace the resistor in the tach with a variable one so you can calibrate the tach. The resistor loses it resistance over time and causes the tach to read too high.
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peterh
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Report this Post02-19-2015 08:19 AM Click Here to See the Profile for peterhClick Here to Email peterhSend a Private Message to peterhEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have similar problem with my 1986 Fiero. It has always read about 30% to high and now reads approx. 40% high due to deterioration of the electric components over time.
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