tachometer issues

[Doodie99]

So I have a Cat 3208 with a teleflex gage that I got running after many years dormant. The gage does not zero when I apply power and when I started the engine it was reading around 1100rpm ~ it does react when I go higher to 2k or 2500 but does not go much below 1k even without the engine running.
any thoughts on where to go from here? I am thinking the gage is faulty but maybe some thoughts on it?

[Bmarler]

Is that tach a universal type? If so, there might be a rotary switch on the back side that’s used for calibration. Sometimes rotating that a few turns will solve problems with the readout. Be sure to note the position you started from.

[Doodie99]

Originally Posted by Bmarler

Is that tach a universal type? If so, there might be a rotary switch on the back side that’s used for calibration. Sometimes rotating that a few turns will solve problems with the readout. Be sure to note the position you started from.

I didn't see a switch but it has two hole covers. one is the bulb but the other may be a switch... I'll check.

[Doodie99]

Looking at pictures I took it looks to have a wire that is moved from 8,6,4 for different configurations. maybe just a bad connection?

[mike66]

Can you stick a screwdriver in one of the holes to adjust the pointer? My Motorola tach has one.

[Doodie99]

It has some holes but I am not sure if they are adjustment holes.
I'll look closer.

[diver dave]

If all else fails, i have a new Faria diesel tach that needs a home.

[Bmarler]

Originally Posted by Doodie99

Looking at pictures I took it looks to have a wire that is moved from 8,6,4 for different configurations. maybe just a bad connection?

possibly. my teleflex that had the rotary would read erratically. not just stop at a certain point.
could very well be a different a different problem altogether. the movement might be sticking as a result of the long period of inactivity. some people with lots of patience and tiny tools can service the movement in those, i'm not one of those people. whenever i try, i inevitably screw something up with my heavy handedness.
as was mentioned, if you can spot the adjustment screw for zero, you might have some luck. you'll probably need to remove the innards from the housing to access.

[Doodie99]

Originally Posted by Bmarler

possibly. my teleflex that had the rotary would read erratically. not just stop at a certain point.
could very well be a different a different problem altogether. the movement might be sticking as a result of the long period of inactivity. some people with lots of patience and tiny tools can service the movement in those, i'm not one of those people. whenever i try, i inevitably screw something up with my heavy handedness.
as was mentioned, if you can spot the adjustment screw for zero, you might have some luck. you'll probably need to remove the innards from the housing to access.

I did look at it closer last night and it has a wire to select 8,6,4 and it looks to have calibration on each. I tried to get the one for the 8 cyl to zero and its does not Zero. I may give it more effort tonight. it does look like it will disassemble so I'll give it a try. If I make it worse it at least I gave it a fair shot. I'm pretty good with delicate electronics.

[Doodie99]

Originally Posted by diver dave

If all else fails, i have a new Faria diesel tach that needs a home.

So i may be interested in the Faria.
Send me a PM

[Doodie99]

Just an update on the Tachometer
It looks like the gage has a zero issue.
it will not Zero with power applied or without.
It moves freely but does not go back to anywhere near zero.
I took it apart as far as I can and the magnetic memory zero point is off.
Time for a new gage.

[Bmarler]

Originally Posted by Doodie99

Just an update on the Tachometer
It looks like the gage has a zero issue.
it will not Zero with power applied or without.
It moves freely but does not go back to anywhere near zero.
I took it apart as far as I can and the magnetic memory zero point is off.
Time for a new gage.

i think you've done all you can. sometimes it's just over. can't say you didn't try though.

[Doodie99]

So I am picking up a new Faria Tach and is there a reliable way to check the accuracy of it once installed. I am fairly new to Diesel engines and i never knew how many different ways diesels check RPM till my tach didn't read correctly. What I know is its a 3208 with a tach drive sensor off the cam. I would think if I checked with an optical tach I could confirm its reading correctly?

[C lectric]

Yes, one of the laser pointer digital phototachs from Ebay or Amazon or the local auto parts place for ~ $20 would be a good way to check.

[Bmarler]

you can also download a free strobe app for your phone. put a marker on the crank pulley and point the strobe at it. i do this every now and then and it works well.

[Comodave]

I just installed new VDO tachs in my boat. Real PITA to get them programmed. I read the instructions multiple times and then sent them to Lauterdale Speedo and had them do the programming. We launched today and so far they look to be working.

[Atlantic Rich]

I think you hit the nail on the head. I worked at
Faria for 27 years and have some knowledge. Most tachs, I believe the Teleflex use a return to zero magnet. It may be that it has dislodged or it's actually possible for it to lose its force in with case it would not zero and wouldn't calibrate properly. A new tach is in order.

[Doodie99]

Originally Posted by Atlantic Rich

I think you hit the nail on the head. I worked at
Faria for 27 years and have some knowledge. Most tachs, I believe the Teleflex use a return to zero magnet. It may be that it has dislodged or it's actually possible for it to lose its force in with case it would not zero and wouldn't calibrate properly. A new tach is in order.

Well i took apart the tach to a point it won't go back together but wanted to know what happened... it does seem like it lost it's magnetic memory. i checked my bridge tach and it too has lost its zero. i guess 20 years of sitting at 1k made it stay there... its not frozen because it does move but i don't think i will ever get it back. Well my new Tach arrived and it should work.