Speed Posted July 20, 2007 Share Posted July 20, 2007 I have located an electric tach I want to use on my truck,since it's a 12 volt unit and only has a 0 to 4,000 rpm scale. My problem with this is:This tach is designed to be triggered by the alternator-can it be set to trigger from my coil,as a regular gas engine tach would? How do these Alternator driven tachs work? Seems to me it'd be like running your distributor off a v-belt drive-it couldn't possibly stay accurate. I can probably run it off the alternator on the ,but if I can make this work off the coil on my I might get another one for my GMC dump truck. Thanks! Speed Quote "Remember-ANY Gun Control is Unconstitutional!"<!--sizeo:3--><span style="font-size:12pt;line-height:100%"><!--/sizeo--><i><b>MACK-E Model Registry # 36</b></i><!--sizec--></span><!--/sizec--><a href="http://www.nvabatetravel.com/"target="_blank">http://www.nvabatetravel.com/</a> Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/ Share on other sites More sharing options...
Maxville Truck Posted July 20, 2007 Share Posted July 20, 2007 Speed, I believe that the alternator trive tachs are designed to operate at a higher "frequency" than the coil driven tachs, the alternator spins several RPM higher than the engine, therefore the "calibration" is set differently internally, If your tach has any dip switch settings on the back of it it may be possible to adjust the operating "frequency". IE, if the alternator output is 50 pulses per rotation and is turning at 5 times the the rpm of the engine it would have a "frequency" of 250 per one RPM. your coil frequency for a 6 cylinder would be 3 per one rpm. some one will probably correct me on this..... I had a alternator tach one time on a pulling tractor that straped to the outside of the alternator with and inductive pick up. it was very inaccurate, especially if the belt slipped, or the alternator load changed..... Quote Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/#findComment-13047 Share on other sites More sharing options...
Freightrain Posted July 25, 2007 Share Posted July 25, 2007 You'd be better off finding a "car" type aftermarket tach and just wire it to the coil. Much simplier and more accurate. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/#findComment-13113 Share on other sites More sharing options...
Speed Posted July 26, 2007 Author Share Posted July 26, 2007 I know-it just seems kinda punk to have a tach that goes to 8,000 rpms hooked up to an engine that won't see 3,600. Kinda depressing... Speed Quote "Remember-ANY Gun Control is Unconstitutional!"<!--sizeo:3--><span style="font-size:12pt;line-height:100%"><!--/sizeo--><i><b>MACK-E Model Registry # 36</b></i><!--sizec--></span><!--/sizec--><a href="http://www.nvabatetravel.com/"target="_blank">http://www.nvabatetravel.com/</a> Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/#findComment-13130 Share on other sites More sharing options...
Maxville Truck Posted July 27, 2007 Share Posted July 27, 2007 Speed!!check this link out, (JC Whitney) http://www.jcwhitney.com/autoparts/Product...0002124/c-10101good luck Quote Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/#findComment-13144 Share on other sites More sharing options...
Speed Posted August 6, 2007 Author Share Posted August 6, 2007 Speed!!check this link out, (JC Whitney) http://www.jcwhitney.com/autoparts/Product...0002124/c-10101good luck THAT'S IT!!! That's exactly what I've been looking for! It indicates in the link that a mounting cup is available,too. Thanks! Speed Quote "Remember-ANY Gun Control is Unconstitutional!"<!--sizeo:3--><span style="font-size:12pt;line-height:100%"><!--/sizeo--><i><b>MACK-E Model Registry # 36</b></i><!--sizec--></span><!--/sizec--><a href="http://www.nvabatetravel.com/"target="_blank">http://www.nvabatetravel.com/</a> Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/#findComment-13276 Share on other sites More sharing options...
Greg Rider Posted September 25, 2007 Share Posted September 25, 2007 THAT'S IT!!! That's exactly what I've been looking for! It indicates in the link that a mounting cup is available,too. Thanks! Speed Speed,that tach I believe is made in the USA!!!I called JC Whitney a few years ago asking about a low revving tach and they told me it was made in Pa. Quote #1 on A-model registryIf I drink because of work, why can't I drink at work? Link to comment https://www.bigmacktrucks.com/topic/2672-another-tach-question/#findComment-14143 Share on other sites More sharing options...
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