Tarheel Blue Posted May 23, 2023 Share Posted May 23, 2023 A bit concerned that the tach is sitting at 1300 R's with no input. So it may be stuck or way out of calibration. If the latter you can pull the needle off and put it back on at 0. But you can test by installing three jumpers: Power: The lower right connector is B+ and that goes to 12v Ground: The upper right connector is ground Ignition: The upper left connector is for the signal in and it goes to the low side of the coil, which is labeled Tach and will be DG/Y wire. Here's what some of the tachs say on the back: Thanks Gary. It didn’t even register with me that the needle is sitting @ 1300. To be clear, I’d still need to have a running engine to connect the jumpers to, or is there a way to simulate the DG/Y tach signal? Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 23, 2023 Share Posted May 23, 2023 Thanks Gary. It didn’t even register with me that the needle is sitting @ 1300. To be clear, I’d still need to have a running engine to connect the jumpers to, or is there a way to simulate the DG/Y tach signal? Yes, the engine has to be running. But there is a chance you could simulate a running engine by connecting the signal wire to positive/disconnecting/connecting RAPIDLY. That will only provide 12v instead of the much higher voltage that the coil creates, something like 50v if I remember correctly, but it might work. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted May 23, 2023 Share Posted May 23, 2023 Yes, the engine has to be running. But there is a chance you could simulate a running engine by connecting the signal wire to positive/disconnecting/connecting RAPIDLY. That will only provide 12v instead of the much higher voltage that the coil creates, something like 50v if I remember correctly, but it might work. It might only make the tach needle jump though instead of read anything. Link to comment Share on other sites More sharing options...
Tarheel Blue Posted May 23, 2023 Share Posted May 23, 2023 It might only make the tach needle jump though instead of read anything. Ha! At my age there are very few things that I can do RAPIDLY! Good to know for future reference, however I’m going to pass on this one. Too many ifs and buts, and you know what they say about candy and nuts! The counter man says that he’s pretty sure he has a couple more trucks he can look at, it just might be a few days before he can shoot me some more pictures. Fingers crossed. Link to comment Share on other sites More sharing options...
1986F150Six Posted May 24, 2023 Author Share Posted May 24, 2023 Ha! At my age there are very few things that I can do RAPIDLY! Good to know for future reference, however I’m going to pass on this one. Too many ifs and buts, and you know what they say about candy and nuts! The counter man says that he’s pretty sure he has a couple more trucks he can look at, it just might be a few days before he can shoot me some more pictures. Fingers crossed. Another listing with a suspected bad tachometer, due to needle position: https://www.ebay.com/itm/314602986191?epid=1786871364&hash=item493fcc9acf:g:a1UAAOSww4ZkaNmt&amdata=enc%3AAQAIAAAA0NxiE5GRaH5FWqc32xkPzYWiaBdCs%2BKAz%2FJ%2FdJ3hVPHin3i29ocMs%2BqnFfyLxvtqrptI3%2BKhgDGH7JaTkkExVRN9p7wA7YNE5p0b9w9hsfEA0TY5vL6gey6V69OBPVjlI1oargMYk2rAtCjxUZ3OxwyGdYboqiuhY%2FB25s1YEbLmu1bEKFollnfUjKzF0CVXA7eGl0jhC5J1ifgeiyjFq%2B7lZxsHAm7CpYMfIuwXXLucCOmKE%2B%2FFMz2FhLRAohhtjI8RZWCB0cHgrL84f1qO2%2Fs%3D%7Ctkp%3ABk9SR6CsiuWJYg Link to comment Share on other sites More sharing options...
Tarheel Blue Posted May 24, 2023 Share Posted May 24, 2023 Another listing with a suspected bad tachometer, due to needle position: https://www.ebay.com/itm/314602986191?epid=1786871364&hash=item493fcc9acf:g:a1UAAOSww4ZkaNmt&amdata=enc%3AAQAIAAAA0NxiE5GRaH5FWqc32xkPzYWiaBdCs%2BKAz%2FJ%2FdJ3hVPHin3i29ocMs%2BqnFfyLxvtqrptI3%2BKhgDGH7JaTkkExVRN9p7wA7YNE5p0b9w9hsfEA0TY5vL6gey6V69OBPVjlI1oargMYk2rAtCjxUZ3OxwyGdYboqiuhY%2FB25s1YEbLmu1bEKFollnfUjKzF0CVXA7eGl0jhC5J1ifgeiyjFq%2B7lZxsHAm7CpYMfIuwXXLucCOmKE%2B%2FFMz2FhLRAohhtjI8RZWCB0cHgrL84f1qO2%2Fs%3D%7Ctkp%3ABk9SR6CsiuWJYg Sent seller a question about that issue. Link to comment Share on other sites More sharing options...
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