VDO Tach/Hourmeter

[Jay S]

Recently I replaced my port side raw water pump, and upon running the engine (4BTA) for the first time after the install, I noticed that the hour meter in my tach (analog) was not working. The tach itself was working properly.  The hour meter was working prior to pump replacement. I don’t have a schematic of the control of the hour meter (what turns it on).  Is it controlled by just the key switch, or is it somehow controlled by the alarm control module (# 3913622), or is it tied into the oil pressure switch, or something on the engine that I might have dislodged, while replacing the pump. I am looking for a schematic that includes both the alarm controller, engine wiring harness and gauges. Any help would be greatly appreciated.

Thanks,

Jay

Topic

[Mike Uliasz]

Corey at SBMAR did have some used VDO tachs too, that was second option I was considering if I could not get the tach fixed.

[steve_finney]

Thank you for the insight Mike.

I think it will be best to just find an hour better that fits the available panel slot and was wondering if there was a recommendation on a gauge that would fit in easily.
If no easy fit, I may go down your path.
Thank you again for the effort to reply,

[Mike Uliasz]

Steve,
If you’re going to remove the tach and open up it up like Rob recommended:
(1) look into opening up the tach and replacing the failed plastic gears

I’d do a test with the hour meter to see if it’s the connections before replacing.

Remove the tach’s top plastic cover, then the RPM pin, then the second cover. The hour meter will be attached to the 3rd layer, the back side of the rpm display. Remove the hour meter, then install the hour meter back into the tach without the RPM display (4 wires off hour meter into the tach body). Hook it backup with no covers/display and start the engine and see if it works.

Long story short, fixed a tach/RPM issue (pin falling off), but when I reassembled the hour meter did not work, so had to reassemble multiple times because the tach/hour meter assembilily was slightly out of line and the hour meter moved slight to loose it’s connection.

[steve_finney]

Hour meter addition

Both of my hour meters have finally given up. I was relying on one, but now both have stopped working.

Any recommendations for an hour meter that could fit into the blank VDO slot on the 6BTA instrument panel (see attached photo)?

[Don Mc Donald Jr.]

^Cummins 6BTA-315/330 33Ft. Egg Harbor

The tachs work fine and both hour meters have stopped working last year from the previous owner.

Taking the panel off on the bridge non of the wires are marked to the instrument panel.

The gauges are from 1998 when the 1983 Egg Harbor engines were switched to Diesel.

The engines have about 990 hours on them at present. I was thinking the easiest way is to place electric gauges off the key when the ignition switch is on the hour meters are on. Any special way for the wiring if I go this way.

A wiring diagram would be helpful. Any suggestions on replacement of the compete tach and hour meter units from Cummins would be appreciated.

[howqua11]

Similar problem with my hour meters.

I purchased a Bertram 35 with 6BTA’s 12 months ago. Both hour meters (VDO dual tacho and hour meter) were not working, and the previous owner undertook basic investigations and fitted 2 independent hour meters. What is interesting is that both hour meters in the cabin stopped within 2 hours of each other at 725, and both on the flybridge at 695 & 696.

12 volts is measured at the tacho connections with the key on, and normal tacho indications are displayed.

Any further comment or advice would be appreciated.

[Rob Schepis]

That’s where I thought you were but was surprised you are still boating.  Tenacious was hauled last week and shrink-wrapped today.

Good that you are running twins so you have the one hour meter for reference..

[Jay S]

Yes, there is an issue with my port engine tach hour meter, starboard engine tach hour meter is working fine.

Marshfield Ma half way between Boston and Cape Cod

Jay

[Rob Schepis]

So going back to your original post – Was there even an issue with the hour meter?

BTW, where is Marshfield ?

[Jay S]

So when the key is turned on and the gauge gets it voltage, it still needs the signal voltage (which comes in on the grey wire), which in turn closes a switch (located inside the tach itself) thus starting the hour meter.  I thought that it would be just the key on would start the hour meter, but when I turned the key on, supplying the 12v on my starboard engine to see if the clock would run, it did not, but when the engine started, the clock did moved.  I get the picture now, but just wanted to get other people’s input, jus to make sure.

Thanks again,

Jay

[Corey Schmidt]

IGN

If I had to guess, I would say say that when the hour meter see’s 12V from the IGN (purple wire) the clock is running… I don’t think it gets any more complicated than that…

[Rob Schepis]

Yes, purple is “key-on” 12V that feeds all of the gauges.  Any “controlling” of the hour meter is within the tach itself andI believe the tach needs an actual running signal input for the hour meter to run.

[Jay S]

Thanks for the reply Rob,  looking at the schematics, it looks like the hour meter gets its power from the purple wire from key switch being in the on position, even without the engine running.  Am I correct in assuming this, or is there something on the engine that closes another switch to start the hour meter.

Thanks for the schematics.

Jay

[Rob Schepis]

If your tach is still operating it simply sounds like a coincidence that your VDO hour meter went out at the same time you replaced the raw water pump.  The VDO tachs are known for the hour meters crapping out over time.  You can (1) look into opening up the tach and replacing the failed plastic gears, (2) add a separate stand alone hour meter or (3) replace the tach unit with a new analog or an Aetna digital.

Here is the wiring diagram section of sbmar:

http://www.sbmar.com/cummins-marine-diesel-engine-wiring-diagrams/

[Author]

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