View Full Version : AEtna Digital Tach not working
I am sitting at the dock getting ready to leave the slip and I see the digital readout on my Aetna digital tach drop to 0 and I see the hour meter in the tach stop spinning. So, at this point, I do not know whether the tach cable is bad, the tach drive is bad, the tach itself is bad or what. I tried to jump the wires on the fuel pressure sender and the hour meter in the tach did not run. I think it has to if that tach is good but I am not sure. Also, the actual drive coming off of the Detroit has a lot of play init. I am not sure whether this is normal. Finally, although it may mean nothing, without the tach working on that side, the slave side, the Glendinningmsynchronizer will not let the slave throttle act as a slave. So, with all of that said, is there is an way to figure this all out without swapping tach drives, tach cables, and the tach itself.
You should see some AC voltage coming out of the sender mounted on the Glendinning. If not, it is the sender or the little key in it. Glendinning or Lauderdale Speedo can help you out further. Been here , done this.
George- is there a way to tell if the sender on the tach cable mounted to th e engine is working properly?
Unscrew the cable at the Glendinning from the offending engine and see if the end spins. If not, unscrew it from the engine (at the little 90 degree fitting). You can turn the end of the cable there, and see if the other end turns (if not, broken cable). Last suspect is the aforementioned fitting itself. I had one fail recently, and replaced them both. Glendinning had the parts. They are great for walking you through this whole process and have all the parts except the electronic senders, which they will send you to LS Speedo for.
Disclaimer: I do not have Aetna Digital tachs, just their senders. If there is some nuance to the digital tachs, I must defer to Glendinning or LS Speedo.
Thanks. I now realize that the hour meters in the digital techs work off of minimum risks and have nothing to do with the pressures switch. I will also check my tach on the tower which is jumped off of the one below. If that works, then it is the tach below. If not, then either the tach cable or the sender.
It seems to me that the Glenning operation should,not be affected by the tach not working if the mechanical tach cable is working properly. Is that right? If so, the fact that thevGlendinning is not working properly would point either to a bad tach cable or a bad drive rather than a bad sender?
Yes, that's correct, I'm sorry. I was a little confused reading your post. This is exactly what happened to me a couple months ago, I discovered the Glendinning not working and traced it back to the L fitting on the engine. Went ahead and replaced them both, from Glendinning. New ones have a zerk fitting for lubing. But we had to trace it back to make sure the cable was good and the little keys in place, which apparently are the more common points of failure.
Traced it all out today and we discovered that it was the Aetna tach sender that fell apart. Easy and inexpensive fix. Thanks for the help.
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