INFO: 72 - 79 Gauge Clusters and Wiring

It's  been 'stickied'. Not going anywhere. One of the admins at Ranchero.us gave us his permission to use his thread so I copied the pictures and moved it here.. :)

This is a sketch of the parallel tach used in the '77 through '79 models and some '76 vehicles as well:

Part 5:

Wiring:

This is the factory harness that connects the harness on the back of the cluster to the engine wiring harness:




This is the factory engine to fuse block harness that contains the integral tachometer and ammeter wiring:




For those that are troubleshooting Tachometer or ammeter wiring issues or those retrofitting a gauge cluster into a standard car the following rough sketches show the proper wiring paths:

1972 through 1976 (Green Printed Circuit) Tachometer:





Ammeter: To properly install the wiring for the ammeter you need an insulator junction block, one or two (recommended) 14 Gauge fusible links, 30-36 inches of yellow 10 gauge primary wire, and yellow and red 14 gauge primary wire (approximately 12' of each). Install the insulated junction block on the flat boss under the starter solenoid, take the original primary wiring off of the starter solenoid and attach to the insulated junction block, then install the shunt per the diagram below:





For those that are retrofitting a gauge cluster into a standard dash car you need to change the oil pressure switch with an oil pressure sending unit and then install the tachometer and ammeter wiring above. The final item required is to tap off of your cigar lighter power feed (light blue / white stripe) for clock power.

Part 3:

6 different printed circuits were used across the groups. 4 of the six will be shown here, '77, '78 and '79 each had it's own engineering number on the circuit however, the wiring and pin outs appear to be the same.

'72 and '73 and the '74 and '75 printed circuits. Some 1976 models had the '74 and '75 cluster with printed circuit:



'76 and '77 - '79 Printed circuits: High series 1976 had a unique printed circuit that could also be found in some '77 - '79 series vehicles. This was dependent on options installed with these cars:




The gauge layouts differed between the year groups as well:



Tachometer and indicator lights differed through the year groups '72 - '76 Green Printed Circuit Tachometers are serial tachometers:

Taken from Ranchero.us, with permission from 72GTVA

<My thanks to Spence, Dan, Rob, HR, Clark, and others for their inputs to this article.

If you see an area that needs expansion or if you have questions, PM or email through the site.

Part 1:

While they look similiar, there are a lot of differences in the '72 to '79 Gauge Groups that merits explanation. There are, in fact, 4 distinct groups of these clusters and there is a mixture of them between the model year cars. '72 and '73 are unique to those years, '74 and '75 are also unique to those years although some of these same clusters are found in '76 models. '76 "high" series was unique to the cars it was installed in, and '77 to '79 had some variations in those years as well. Be warned that when you purchase one of these for an upgrade or to replace your existing but deteriorating dash you may be in for some surprises.

These are the main groups:

Front:



Back:




These are the gauge covers for comparison, it should be noted that for some 1974 models depending on DSO code they did not have the "UNLEADED FUEL ONLY" branding on the fuel gauge, all US Market 1975 and up did.



The '72 and '73 Gauge Clusters used metal gauge face trim pieces and edge lighting to identify the gauge functions. This is the unique '72 and '73 Gauge Cover with associated pieces:




Edited by Psquare75 - 05-January-2010 at 4:37AM