During the rewiring, I added these 4-pin connectors to make the cluster more modular. Note that the ICVR has 2 terminals on its hot side, so tapping that circuit for the voltmeter will be simple. The black ground wire in the bare spade terminal goes to one of the cluster faceplate screws (but it might be better under the ICVR mounting screw).
IF THE IMAGE IS TOO SMALL, click it.
See also:
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https://www.fleet.ford.com/truckbbas/non-html/1997/c37_39_p.pdf 
![voltmeter16.jpg During the rewiring, I added these 4-pin connectors to make the cluster more modular. Note that the ICVR has 2 terminals on its hot side, so tapping that circuit for the voltmeter will be simple. The black ground wire in the bare spade terminal goes to one of the cluster faceplate screws (but it might be better under the ICVR mounting screw).
IF THE IMAGE IS TOO SMALL, click it.
See also:
[url=http://www.supermotors.net/registry/media/843356][img]http://www.supermotors.net/getfile/843356/thumbnail/wiringdiagrameb3g.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/870470][img]http://www.supermotors.net/getfile/870470/thumbnail/3gswap.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/843907][img]http://www.supermotors.net/getfile/843907/thumbnail/alternator3gvr.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/849725][img]http://www.supermotors.net/getfile/849725/thumbnail/fusesblades.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/830776][img]http://www.supermotors.net/getfile/830776/thumbnail/fusiblelinkrepair.jpg[/img][/url] . [url=http://www.supermotors.net/registry/media/832986][img]http://www.supermotors.net/getfile/832986/thumbnail/bulbsfuseswire.jpg[/img][/url] . [url=http://www.supermotors.net/vehicles/registry/media/874262][img]http://www.supermotors.net/getfile/874262/thumbnail/ebbodyinstruments-b.jpg[/img][/url]
https://www.fleet.ford.com/truckbbas/non-html/1997/c37_39_p.pdf](https://www.supermotors.net/getfile/910354/fullsize/voltmeter16.jpg)