Help!! Factory tach conversion - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Iliveforthis · 01-26-2013, 08:23 PM

I have an 87' short box 4x4 with a three speed manual , it came factory with the 5" speedo and 5" fuel gauge with warning lights, picked up a gm NEW factory tach, with gauges , I was under the assumption it was the same pigtail plugging into the back of the cluster and might have to change some senders and hook up the tach wire obviously, well I've done that and I have NOTHING, speedo (mechanical) works obviously but all the gauges are pegged except the fuel gauge reads 1/4 but it's full, also the rh blinker indicator light is in as soon as the key is on and stays that way, also no blinkers working inside or outside, is there a diff pigtail for the factory tachs that anyone knows about? All help is appreciated thanks
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jbristo67 · 01-26-2013, 11:14 PM

My 67 just had idiot lights. I know when I put the tach cluster in it I had to change the whole fuse box and wiring harness.
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ray_mcavoy · 01-26-2013, 11:56 PM

Yes, trucks with factory gauge clusters (with or without the tach) have the wires in the cluster plug arranged in a different pinout configuration than trucks with the warning light clusters.

See the factory wiring diagrams that hatzie posted at --> http://67-72chevytrucks.com/vboard/s...d.php?t=545416

You can "re-pin" the cluster plug to match the factory gauge cluster configuration and that should take care of your problems. Do that by labeling all of the wires (using the warning light cluster diagram). Then carefully remove the terminals from the plastic connector housing (do that by depressing the latching tang using a tiny screwdriver or pick). Then re-insert them into the appropriate slots (this time using the diagram for trucks with factory gauges).

EDIT: What I just posted above is assuming your new gauge/tach cluster is meant for a 1978-1987 pickup truck. The 73-75 & 77-76 clusters (and clusters for medium duty trucks) each have thier own differences that would require additional wiring changes.

Iliveforthis · 01-27-2013, 11:22 AM

Thanks for the help, that makes sense and yes is for the 80's pickup
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motornut · 01-29-2013, 12:04 PM

should look kinda like this

**hatzie** · 01-29-2013, 12:52 PM

Instrument cluster plug pinouts from the 73-87 FAQ.
http://67-72chevytrucks.com/vboard/s...d.php?t=456877

01-26-2013, 08:23 PM	#1
Iliveforthis Registered User Join Date: Feb 2012 Location: Fernley, nv Posts: 2	Help!! Factory tach conversion I have an 87' short box 4x4 with a three speed manual , it came factory with the 5" speedo and 5" fuel gauge with warning lights, picked up a gm NEW factory tach, with gauges , I was under the assumption it was the same pigtail plugging into the back of the cluster and might have to change some senders and hook up the tach wire obviously, well I've done that and I have NOTHING, speedo (mechanical) works obviously but all the gauges are pegged except the fuel gauge reads 1/4 but it's full, also the rh blinker indicator light is in as soon as the key is on and stays that way, also no blinkers working inside or outside, is there a diff pigtail for the factory tachs that anyone knows about? All help is appreciated thanks Posted via Mobile Device

01-26-2013, 11:14 PM	#2
jbristo67 resident oilfield trash Join Date: Jan 2009 Location: Lubbock TX Posts: 1,465	Re: Help!! Factory tach conversion My 67 just had idiot lights. I know when I put the tach cluster in it I had to change the whole fuse box and wiring harness. Posted via Mobile Device __________________ 1967 SWB C10 396/400 factory air factory tach (sadly had to send to a new home) 1986 Honda 70 Fourtrax 1991 Chevrolet K5 blazer 2wd 1982 Mastercraft Pro Star 190 Stars and Stripes 2002 Chevrolet Tahoe 2011 Nissan Armada

01-26-2013, 11:56 PM	#3
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,354	Re: Help!! Factory tach conversion Yes, trucks with factory gauge clusters (with or without the tach) have the wires in the cluster plug arranged in a different pinout configuration than trucks with the warning light clusters. See the factory wiring diagrams that hatzie posted at --> http://67-72chevytrucks.com/vboard/s...d.php?t=545416 You can "re-pin" the cluster plug to match the factory gauge cluster configuration and that should take care of your problems. Do that by labeling all of the wires (using the warning light cluster diagram). Then carefully remove the terminals from the plastic connector housing (do that by depressing the latching tang using a tiny screwdriver or pick). Then re-insert them into the appropriate slots (this time using the diagram for trucks with factory gauges). EDIT: What I just posted above is assuming your new gauge/tach cluster is meant for a 1978-1987 pickup truck. The 73-75 & 77-76 clusters (and clusters for medium duty trucks) each have thier own differences that would require additional wiring changes. Last edited by ray_mcavoy; 01-27-2013 at 12:08 AM.

01-27-2013, 11:22 AM	#4
Iliveforthis Registered User Join Date: Feb 2012 Location: Fernley, nv Posts: 2	Re: Help!! Factory tach conversion Thanks for the help, that makes sense and yes is for the 80's pickup Posted via Mobile Device

01-29-2013, 12:04 PM	#5
motornut 78K & 79C Jimmys Join Date: Nov 2009 Location: Ottawa Ont CANADA Posts: 7,901	Re: Help!! Factory tach conversion should look kinda like this Attached Images __________________ John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350

01-29-2013, 12:52 PM	#6
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,912	Re: Help!! Factory tach conversion Instrument cluster plug pinouts from the 73-87 FAQ. http://67-72chevytrucks.com/vboard/s...d.php?t=456877 __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.



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