Tach Troubleshooting

[wndsr]

Can someone educate me as to the proper way to troubleshoot an inoperative tach? The stb tach quit working and I would like to narrow it down to the tach or the feed from the sync? The port tach works but testing the wires on the back with a test light wasnt the answer. These are electric tachs and a Glendening synchronizer.
Thanks
Ben

 

[Captcoop]

I don't think that the sync. drives the tach. The tach is driven by a pulse generator on the front of the engine in most cases. I would locate it and remove the wire, unscrew the pulse generator and remove the drive tang, usually a plastic key that turns the generator if it is broken or striped replace. I have found them @ NAPA or DD.
Good Luck

 

[Werner Schoenknecht]

Please tell us the year of your boat. Our 1986 43 MY with DD. has a mechanical cable [similar to the old speedometer] from the engine to the sync and from the sync to the tachs via wires. Just replaced one of the cables and got them from Glendinning thru our local dealer. I made all the arrangements 843-399-6146. One of our tachs went bad and we ordered them from Sam's and they required new puls generator plus wires. Routing the wires was not a big deal.
Werner Schoenknecht- Mirage

 

[stewart]

My port tack quit ,871, it was stripped gears in the tack drive to the glendenning syncronometer , got a new drive from Sams $200 arrived today.
Cheers Stewart

 

[GJH]

You need to put a multimeter across the outputs of the tach sender (which IS mounted to the synch) and test for AC voltage, not DC. If you don't get a reading the sender is bad, often times just the little key drive.

What does your sender look like? Glendinning sometimes has some of the key drives for the old Suns, or new whole new sender runs about 85 bucks, at least they did for mine. Very easy fix.

 

[newinlet]

Can you just switch tachs put the good one where the bad one is . if it works its the tach. if not it is something else.
My port tach reads about 200 prm shy wot under load, Can I swap tachs to see if the rpm issue follows the tach. BTW there are signs of rust at the bottom of the suspect bad tach and sometimes I can get 2500 out of that tach. I know I can use a hand held in the ER but swapping the tachs would be easy

 

[wndsr]

George, Sounds like you are on the right track for my set up. I will test for voltage going to the inop tach. If I get no reading, I assume I will then verify that the cable coming from the engine to the sync is operational. I am thinking it is ok because the sync works fine, just no tach from that engine. If so, then it is reasonable to assume the tach generator is bad. Is this the right understanding? As mentioned also above, I could jump the wires from good tach to bad, I just preferred to "do it right" rather than start trying things.
Thanks for all the help.
Ben