Tagged: tach stops 3000rpm
June 15, 2023 at 2:50 pm #99193
I have recently noticed that my tach is stopping at 3000rpm. It seems working and accurate up to that point. I have pertronix electronic points installed in stock distributor and matching pertronix coil.
Could it have been like this for a long time? Absolutely! since my memory is not what it once was. But it is now bugging me and any advice or memory assistance would be appreciated.
I vaguely remember having a TV repair guy replace a transistor about 25 years ago, I think that was in the tach, but not sure. I also have the electronic voltage stabilizer installed from many years ago.
Has my tach gone bad?? Has something come loose under dash?
Kinda humbling to not remember all these things I did 25 years ago.
June 15, 2023 at 10:20 pm #99194
So I am going to answer your question by asking a few questions. The answer should be in there somewhere. You won’t have to remember 25 years ago. I can’t remember that far back either. Here are the questions;
1. Does the needle swing up to 3K (or about) and stop dead?
2. Does the needle swing up to 3K (or about) and float around that area?
3. Has the tach ever worked correctly? OOPPS, that was more than 25 years ago. Probably forgot!
A few comments. A needle that sticks at a given point does so because there is dirt in the movement. If inaccurate or the needle is sluggish, the tach electronics is defective.
In general, a stock tach will not work accurately with Pertroncx if it works at all. Some won’t work with a Pertronix. Seems like yours at least works a little bit.
The fix is to change the electronics in the tach. I can do this plus calibrate it so it is accurate at each RPM point. Tach is restored too. $175
June 16, 2023 at 9:31 am #99195
It seems to just stop dead, no float or movement once “pegged” at 3k. So your comment about debris sure seems possible. I think it worked fine at some point in the past 🙂 Maybe I never went past 3K? ha ha
I did replace the old incandescent dash bulbs with LED kit a year or so ago. Now looking carefully at new bulb and tach now that it is removed, it almost seems like the new LED could actually be touching the circuit board, that doesn’t seem like a good idea.
With a little guidance I could try removing the case and looking for debris etc? I will try to attach a pic or two of the back.
I would also be totally happy with sending it to you Tom and have a fresh fully functioning unit to install. I’ll need a current address to send it and we can take care of that offline from the forum. Glad to hear that you are still busy with car tinkering!!!
I would like to get new o-ring for reinstalling as the old one is barely in one piece now. Is there a source for them??
June 16, 2023 at 10:52 am #99197
Updated info: After removing the tach and opening the case, Tom you were correct, debris was stopping the needle. It now moves freely over the full range. I assume this means it really has been working most or at least part of the last 25 years. 🙂
The debris issue needs addressing, it seems the reflective paint inside the case is flaking off, pretty sure that is the source. Suggestions anyone? clear coat the existing paint? Can I get reflective paint to recoat? It also appear the black paint on the center of the needle is starting to flake.
June 18, 2023 at 9:38 am #99214Gary and Maureen CorbettParticipant
Joe – Hi, you can get the 4-inch rubber or-rings from Moss Motors – Part No. 280-890, used on MGA instruments. I just installed them on my Alpine speedo and tach, one under the bezel and another between the instrument and the dashboard.
In regards to the paint it might be just as easy to get a good case from EBay and put your guts in it.
June 18, 2023 at 2:07 pm #99216David HallParticipant
If you prefer to get the “flat” gasket to use on gauges, along with the O Ring type, you can buy them from the original Nisonger office, 914-381-3600, firstname.lastname@example.org. Peter, the owner, still sells supplies and Smiths gauges, but does no repair work. I believe you order them in sets.
June 18, 2023 at 9:15 pm #99219
Joe, if you’ve disassembled the tach this far, you might as well keep going. What can you loose. You likely have the tach out of the case to see the flaking paint, which is a common problem. To refurbish the interior, use sandpaper and sand all the loose white and blue paint off. Note where the blue paint was. Wipe down and spray bomb the complete interior with a bright flat white. Find some baby blue paint and mask. Then spray the blue area.
With tach out, use a small air nozzle to blow out debris around the circular magnet and the D’Arsonval meter movement. Do not blow air on the hairsprings.
Flaking paint on needle. Use your finger to wipe it off. Use a felt tip pen to blacken or if you are the artist type, a thin coat of flat black lacquer. You WILL change the accuracy of the tach if you paint the orange part of the needle.
If you want an O ring, hit a local hadrware store with an O ring assortment. May not be flat but no one will notice when installed. I forgot the size but can check tomorrow if that is the route you would take.
June 21, 2023 at 10:12 pm #99231
I neglected to provide my address should you want a tack restoration with circuitry updates to improve accuracy. Tach will be fully restored to its original inside and out. appearance.
1924 Blacks Bridge Road
Annville, PA 17003
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