Picked up a 6K tach and seperately picked up a red 6Cyl 4cycle 12 sender(nos). Trying to get it working on the bench. The tach does not have any reading. I think there is a battery in the sender and would like some help with pic's or instructions on how to fix it. I opened the sender the item that looks like a battery has NO numbers of any kind on it. No polarity marker either and it is soldered in. I am quite comfortable with installing a battery holder or devising a 12V powered power source for it. But need to know what voltage to aim for. Also willing to document and make a video for other to use in the future. Who can help me?
Might help if we knew the model of the tach and the model of the sender that you have. Might not even be compatible, seeing that they were picked up separately. . A 900 Series sender: A 465 Series sender on top of fuse panel :
More pics of the sender. I think the silver can is a battery. Tach # 429371 sender 429375. And the last one of a favorite tool in my shop Sun 504. Love using it.
Had a chance to check the tach out better. It is quiet when shaken lightly ( no loose item inside). Ohmed the + and - terminals and got a OPEN reading. Not good. Stuck a 1.5V battery on the terminals and got no needle movement. Looks like it is dead. Will open the sealed unit. The bezel is crimped. Any ideas on a good way to do it? Also checked the sender out better, hooked to a tach output on a HEI spun by the 504 Sun. The +/- terminals showed some DC voltage changes but really did not correspond to the RPM and drifted in voltage a bunch, never getting above 250millivolts. I think the silver can is a battery and needs changed. Any tips?
Working on the tach decided you can't hurt a turd by shitting it. So I peeled the bezel off and found a desoldered wire. I resoldered it on and then measured the resistance of the meter and found 79 ohms. Which is correct. Then i took the bad battery out of the sending unit. It is soldered in. rigged up a 1.5V battery to test with and stuck the assy on my Sun 504 dist tester with a HEI in it to give tach signals. The tach now reads, but is way low. So then doubled the battery to 3V and it reads higher but still low. So went to 6V battery and now the tach reads almost perfect. Just putting this out there for anyone that maybe having troubles with a Stewart Warner tachometer. I basically got no help and figured it out.
Here is the final fix for the tach sending unit. After finding it needed 6V internally to operate properly. I ordered a DC voltage dropping power supply. It came from China for 1.83 delivered. Go figure. I bought 4 of them. It is small and installed inside the original can where the battery fit. I used RTV Ultra black to "glue" it down. The ground goes to the case and now 1 extra red +12VDC wire is used. When tested it works perfectly.
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