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Hello all and Happy New Year.

I just bought a used Premier NYC E-8 20-2317-1 which has the 5 volt PS2 electronics. All sounds and features work fine except when I move forward or backward at 1 mph the engine takes off at full speed. When I change the mph to 0 or hit the direction button the engine stops as it should. The engine runs fine in conventional mode. I have changed the sound file, thinking it might be program or flash error, that did not fix it. The tach reader is right up against the flywheel, I compared the distance with another working Santa Fe E-8 PS2/5 volt engine and it's the same distance. I changed the tack reader, by removing it from my good working Santa Fe E-8 installed it on the NYC E-8 and still did not fix it. I even changed out the voltage regulator (though I don't think the VR has nothing to do with speed control), that did not fix it. All wires are snug and not loose, the tach reader is not loose and is very close to the flywheel and the tach reader tape on the flywheel is very clear, clean and no obstructions. Any help would be greatly appreciated, thank you.

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Since you have a working E-8 you know how the engine rev'ing sound ramps up and down proportional to speed - 8 different levels.

On the non-working E-8, as you increase speed from 0 in conventional can you hear the engine rev'ing sound ramp up (and then back down as you lower speed) ... OR does the sound stay at the lowest rev'ing irrespective of speed.

Point being, it's the tach that tells the electronics how fast the engine is moving and hence what rev'ing sound to play.  I realize you've undoubtedly double-checked and triple-checked all the connections/wiring associated with the tach.  But if the rev'ing sound never changes, it's more than likely something related to the tach system.  There are some tach-related components on the main board set that have been known to fail.

BTW, the VR generates 5V which the tach circuit actually uses - but if everything else in the engine is working the VR is obviously not the problem.

Are you handy with a multimeter?  If you have steady-hands and can make close-quarters voltage measurements, you can do some troubleshooting of the tach circuit.  That is, you should be able to see the tach sensor voltage go up and down as you manually turn the flywheel (even on a stopped engine).  That would be my next step if attempting a DIY repair.

Dirty Flywheel?  Check that you wired correct.  Check the wire continuity from the tach reader solder joints back to the seven pin connector.  May have a wire that opened.

Also, put the one you removed from the NYC into the SF and see if it works.  If so it is wiring or board.  So you can also check the solder joints on the 7 pin connector of the 5V board under the gray/blue and orange wire for cracks.  After that, new board.

If you NYC tach does not work in SF, you could have also damaged the SF with heat.  Tach readers can be sensitive and I have had a few new ones I installed not work.  So treat them carefully.  G

Stan2004, thanks for the reply. I did not pay attention to the rpm levels. I just tested again. When I increase the MPH, the engine stays at idle RPM (1 of 8 steps), no matter if engine is at 1 mph or 50 mph, the engine sound is at idle. Any ideas? All wire connections are firm. nothing loose. I am a little handy with a voltage meter and have one, so I will test the VR.


Thanks again.


Thanks fro the reply. The flywheel is clean, no obstructions, the tach reader is about 1mm away from the flywheel. I have a good working Santa Fe E-8 and it's the same distance. I already removed the tach reader from the working SF E-8 and put on non working NYC E-8 and nothing, the same results. also the tach reader from non working NYC was put on SF E-8 and the SF E-8 worked fine. 

Thank you

ps2 5v diesel tach

If you're always a the idle rev level sound (irrespective of speed), then more than likely a fault in the tach circuit.

If I were doing it, my next step would be to make some voltage measurements on the 3 tach wires (gray, orange, blue)...both at the board-set side and at the tach side.  Obviously these are close-quarters measurements and you don't want the meter probes slipping/sliding and damaging anything!   Is the orientation of the boards as shown?  In other words you would access the 3 tach signals from the bottom of the board-pair on the left photo (circled in white), and straight-on to the tach board on the right photo.

The tach circuit is simple.  An IR (invisible) LED shoots a beam at the flywheel.  The LED is on two of the 4 terminals on one "window" of the optical chip facing the flywheel on the tach board.  This should be a fixed voltage.  The other two terminals are to the photosensor on the other "window" of the chip.  The sensor voltage changes depending on reflection of the beam off the white or black stripes.

That's the idea anyway.  Again, this is one of steady-hands-required measurements.  I can take some measurements to give you target values but I won't be able to get to it just now.  

The photo has been updated showing the 3 colored tach wires and the optical sensor chip terminal locations on the tach board where the 3 wires go.  It may be easier to attach the meter probes to the sensor chip terminals.

Measure DC voltage: Gray(+) to Blue(-):  About 1.2V.  This is the LED voltage shooting the beam at the flywheel.

Measure DC voltage: Gray(+) to Orange(-): Sensor voltage varies between Black or White stripe reflection.  Voltage lower when White stripe.  Difference should be about 1V.  Could be 4.5V (Black) - 3.5V (White), or 4.0V (Black) - 3.0V (White), etc.

Note: if you don't read ~1.2V on the LED voltage, don't bother reading the sensor voltage.  There's a problem in the LED circuit or wiring that needs to be solved first!



Images (1)
  • ps2 5v diesel tach
Last edited by stan2004

Stan2004, thanks for the pictures, very helpful. The solder joints look good. I'm thinking the board is bad. I have already changed the tach reader from a good working engine. I also changed the voltage regulator. I'm giving up and boxing it up and will wait until I can buy a used ps2 5 volt engine on ebay or ps2 board. thank you all for your help, greatly appreciated!

Just to be clear, when you changed the tach reader, was this JUST the tiny thumbnail-size tach reader board itself (using the original 3 wire harness and unsoldering-resoldering the 3 colored wires)….OR did you pop-out the 3-crimped pins from the 7-position connector at the PS2 board-pair?

Did you decide making the voltage measurements is too risky or difficult (note I re-posted my picture showing voltage measurements to look for at the tach board).

Hello Stan2004, thank for the voltage number. I changed the entire tach reader by removing the 3 wires from the wire harness, of the good working SF E-8 by popping the wire plug (or connectors) out of the harness and plugged the 3 wrires into the harness of the faulty NYC E-8. Still did not work. I have not measured the voltages on the board yet, will do when I get back home tonight. If the voltages are off, or no voltage is measured on the board. I'm sure it's going to be a bad board. I really appreciate the help. This is a really good site for help and advice...

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