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Wiring for factory tach?


BYBIS

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Hey all, been looking at a 70 MC SS that does not have a factory tach to the left of the speedo.  If I remember correctly, there's a fuel gauge there instead.  Since I'm new to these, I have a couple of questions:  1.  Was the factory tach considered an option in 1970?  2.  If the vehicle did not have a tach, is the wiring still in place for the tach so if someone wanted to change the gauge cluster, they could without changing the entire harness?

Thank you in advance for the help.

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Hey Tom,

If I remember correctly, 

- the printed circuits are definitely different between idiot lights and gauges.

- the wiring harness is different, however based on your wiring skills it can be converted to work. Some wires in the plug that goes into the printed circuit have to be moved around and some new wires have to be made to make the conversion work.

There is lots of documentation on what I am referring to. If you have more questions, just ask. Many of us have done this sort of thing before.

Thanks!!

Mike

 

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These Monte's came standard with idiot lights.  The gauge dashes an option and the circuit boards and wiring were different.

rob

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Picture of my 71 factory gauge package that I swapped with another 71 350 Monte. I also swapped ALL the wiring because it was different.

IMG_0321.thumb.JPG.5e733b4d84964be92a00444d5aaa09d7.JPG

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It’s all posted here. I just went through all this and everybody was great. I just purchased a cluster(sonny) repinned the harness and added the tach wire. Pretty painless for somebody with skills,that just happens to not be me. Electrical is my devil

888F0EF5-3BC6-4FA5-9D69-344C61620881.jpeg

DF3E68E4-C1A8-4A85-8F15-7F53AEF48AA2.jpeg

Edited by Dtret
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Factory tach was an option for 70-72. The brown tach wire goes to the negative post on the coil. Not the distributor. If no tach was ordered the no tach wiring will be present. The full gauge dash used a different harness from what was used with idiot light dash.

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17 hours ago, BYBIS said:

Hey all, been looking at a 70 MC SS that does not have a factory tach to the left of the speedo.  If I remember correctly, there's a fuel gauge there instead.  Since I'm new to these, I have a couple of questions:  1.  Was the factory tach considered an option in 1970?  2.  If the vehicle did not have a tach, is the wiring still in place for the tach so if someone wanted to change the gauge cluster, they could without changing the entire harness?

Thank you in advance for the help.

Hey, Tom,

You can easily convert your idiot light dash to a full gauge dash that is identical to the factory option using a kit and you DO NOT have to replace your current wiring harness, just add a couple of new wires and make some necessary modifications to various specified plug/connector locations. 

There is a seller on eBay named sonnie24 who offers the complete conversion kit to do this (be sure to specify the '70 kit to get the green shaded numerals on your gauges).  The kit includes the tach, analog gauges, wires and a new printed circuit board.  It is reasonably priced and uses quality components, however, the 2-page instructions that come with it assume a lot of knowledge that many of us don't have. 

When I did this conversion on my '70, I sought the help and advice of Darren Bull (LS5), fellow club member who knows first gen Monte dash wiring cold.  Together we developed a detailed set of instructions with diagrams that make the conversion almost fool-proof. 

If you want, send me your email address in a Private Message, and I will forward a copy of that documentation to you in a Word file.  It also contains links to a couple of photo journals on Photo Bucket showing the installation process (including upgrading your dash illumination from the original incandescent bulbs to LEDs and repairing your dash clock while you have the dash apart).  This is not a plug and play conversion so it takes some time and work but the results are very satisfying.  Good luck.

Here are the Before and After shots on my '70:

 

PC084346.JPG

PC174420.JPG

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1 hour ago, RealRed70 said:

Factory tach was an option for 70-72. The brown tach wire goes to the negative post on the coil. Not the distributor. If no tach was ordered the no tach wiring will be present. The full gauge dash used a different harness from what was used with idiot light dash.

Sorry, you are correct. I don't know what I was thinking but the wire is from the coil to the tach. Might have been the couple beers I had before I typed the post.

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Team-  THIS is why I joined this group.  The amount of knowledge y'all just vomited on top of me was outstanding.  I can't thank you enough.  I'm in the middle of trying to decide on one of two to purchase and this type of detail helps me tremendously.  I still can't decide, but I'll figure it out.  Maybe that'll be my next post.

 

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