[whatsnewell]

My Stewart-Warner tachometer stopped working about 2.5 years ago. I would really like to get it working again, but really don't know where the sending unit is, or how to trouble shoot this properly. According to some this SW tach should be wired into the back of the gear driven alternator, but I cannot find any evidence it is connected there. Anyone here have a 6V92TA with a Stewart-Warner tach, besides Prarieschooner?

[Ozarkguy]

Not sure on your setup. However I had a tach generator that drove my SW tach that was driven off the accessory drive. It was mounted in the engine compartment. I found it was froze up. Took it apart , cleaned and lubed the shaft n gears. It's about the size of your fist with cable shaft in and wires out to the tach. Also check the wire as they get old n break

Edit. Appears yours different.

There is a lot of info on the WOGroup about this issue

[whatsnewell]

I have a 6V92 TA mechanical engine.....no DDEC. There are very few wires coming from the engine, except for the alternator. The alternator, and water pump are gear driven. I guess my big question is if I have a VDO type of alternator where would I find the sending unit, and if I have a gear driven sender where would I find it?

[folivier]

Clarke if it is a gear driven tach then you should have a cable like a speedometer cable running from the tach to the engine somewhere. Sounds like a long run but that is how it is on boats. If you can look at the back of your tach and see if it has wires or a single cable.

[Ozarkguy]

http://www.dieselpro.com/images/view.asp...uctId=1434

I could look like this 6v92 tach gen. Or it appears as you said some of the alternators have a sensor.

[prairieschooner]

Clarke,
Not sure about this since I haven't had to repair it yet but typically these Tachometers were driven off of the AC Tap on the Alternator.
OK, we don't have a computer and our Diesels are basically Marine Grade unlike versions that followed. Now when my Alternator quit working so did the Tachometer, not saying that this is the case with you, simply stating what I experienced.
I suggest that you start by having the Alternator Tested so that you can eliminate it. If all is well then take a Great look at the wiring (most likely use an Ohm Meter to check for resistance). Otherwise the Tachometer itself could be the problem.
I don't like changing parts to solve a problem so that is why I am suggesting that you have the Alternator tested. Maybe Richard could chime in her and help with another way to test the Signal from the Alternator.

---

PS my YANMAR Diesel in our boat had a Magnetic Sensor similar to what Jimmy had posted. Don't think that we have one of these but I have been wrong before.

[whatsnewell]

Okay.....Richard found the VDO sensor on the front of the engine up by the Turbo.....is looks like the one Ozarkguy posted a picture of. The part # is 340807/1/3....Ozarkguy, is this the same part number as the one in the picture on the Diesel Pro site? Couldn't find that part on their site, but, obviously, you did because you sent the picture. The one we removed has 3 poles.....two poles for the two tach wires, and a ground pole in the middle. The one in the picture appears to have only 2 poles.

At any rate, I am trying to find a source for the VDO sending unit, and have had no luck so far. If not VDO, then a comparable sending unit....these babies are expensive!

[Ozarkguy]

Ok this is what I'e found: http://www.egauges.com/vdo_indS.asp?Send...PN=340-008

http://marine.vdo-gauges.com/sensors/gen...pulse.html

Looks like it is also used in boats .. http://www.autoelectricservice.net/image...atalog.pdf page 16

Or you may want to give Diesel Pro a call..
http://www.dieselpro.com/electrical-tach...volts.aspx

[whatsnewell]

Thank you Jimmy! That second link is EXACTLY what I have.

[encantotom]

clarke, how about having elaine sit in the engine compartment and put a piece of reflective tape on the fan and have her count the revolutions? that would be cheaper than buying a new sender. she could call you on your cell phone and tell you what rpm it is at.

let me know what she thinks about it. just trying to help...

tom