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I read all the threads on intermittent tachometers. I tried scraping the infamous yellow crud from about 3 different tachs, and tried an additional 2 tachs without scraping. I could not get a tach to work for more than a few days or weeks before it would start acting up. As I was also unhappy with the lack of a decent charge gauge, I contacted Bob at Rocketman's Classic Cougar Innovations (http://www.rccinnovations.com/). He was able to convert the ammeter to a volt gauge and replaced the guts of the tach with new modern parts. The tach was literally a direct replacement, unbolt the old and bolt in the new. The volt meter was a tiny bit harder as the wiring is different (the gauge itself bolts right in). I had to un-pin the ammeter wires from the cluster wiring connector and tape them off and out of the way. I then unpinned the additional ground wire for 8 cylinder from the original tach (not needed with the new tach) and pinned it in to the negative side of the volt meter. Then I ran a new "key on" positive wire and pinned it into the positive side of the voltmeter. All in all a very quick project. I have not had time to test the tach longer term to determine if there could be a problem with my truck and not the many tach's I tried. I am hopeful this is the fix and if nothing else I at least have new tach guts.
New tach, working, No noticeable difference other than needle has been painted.
New volt meter, key off.
New volt meter, key on, engine off, (battery low, needs charging)
New volt meter, key on, engine running.
Last edited by brad1979; Oct 14, 2015 at 08:24 PM.
Reason: Added web address
Jim, I'm pretty sure your write up is where I got the info to do the volt meter swap originally, I didn't want to cut my harness so re-pinning the connector made sense to me as I was only adding 1 wire. I also happened to have a bunch of connector pins I had harvested from an old parts truck. I am not sure what the cost will be for the tach conversion as I think mine was the first one of this style Bob has done. He gave me a package price to do 3 gauges so I am not certain the invoice pricing is accurate. Bob mentioned he will be adding this tach conversion to his website, it would be best to contact him for pricing.
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