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10-30-2013, 10:51 PM
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#1 |
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Registered User
Join Date: Oct 2013
Location: Oregon
Posts: 41
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79 Factory Tach Help
So, my original factory tach hasn't worked in probably 20+ years. When i finally decided to take it out and try to find out why some diodes on the board seemed to be burned up. I found another 79 truck today with a factory tach and was told it worked fine up until the time it was parked, which may have been quite some time ago. Is there any way to bench test these tachs to ensure they work before installing? Any help is appreciated!
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10-30-2013, 11:31 PM
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#2 |
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Registered User
Join Date: Sep 2009
Location: Beaverton, OR from WA State
Posts: 1,515
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Re: 79 Factory Tach Help
Three lengths of wire, 4 female spade terminals and two alligator clips should get the job done... There is a diagram around here somewhere, but the tach connects to a ground, key-on power, and the tach signal at the HEI distributor.
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Devin 1983 GMC High Sierra 2500, 4x4, RC/LB, 400 S.B., SM-465, NP-208, Corporate 10 bolt & 9.5" 14 bolt 1996 GMC Sierra SLE 3500 DRW, 4x4, EC/LB, Vortec 454, NV-4500, BW-4401, AAM 925 & AAM 1050 1997 GMC Sierra SLT 1500 4x4, Z71/F44, EC/SB, Vortec 350 My Introduction with my '83s History New Daily, the '96 |
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10-30-2013, 11:49 PM
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#3 |
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Registered User
Join Date: Oct 2013
Location: Oregon
Posts: 41
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Re: 79 Factory Tach Help
Thanks! Doesn't sound terribly difficult. I'll see if I can find the diagram on here. If anyone finds it before I do please share.
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10-31-2013, 09:47 AM
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#4 |
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78K & 79C Jimmys
Join Date: Nov 2009
Location: Ottawa Ont CANADA
Posts: 7,901
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Re: 79 Factory Tach Help
mine first wasn't stock in my 78,
used this to ease in/out great for testing,and i can plug this one back in to use under the hood hooked to the cluster power,(not threw the firewall like stock would be) pink/black is power black is ground at the Ebrake ground bus and mine used a brown wire for the signal to cap(some are white)
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John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350 Last edited by motornut; 10-31-2013 at 09:54 AM. |
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