[JRP]

Hey guys, been clocking up quite a few km lately and on my last big drive tacho decided to start doing random crap 25 hrs into my 28 hr drive.

I'm running a Dakota digital as it's a ZD to TD conversion. Checked today on the Dakota what RPM the dash would show using the built in test function (meant to send a 2000 RPM signal to cluster) and it was spot on.

Picked up a new multimeter today that can measure frequency and tomorrow I'll take some measurements at whatever connections I can find between the tacho sensor and Dakota to see what PPM I get (there's a thread Ive saved where someone has done the same so I have some rough figures to expect). I have the tacho sensor near the thermostat housing FYI.


Is there anything else I can look at to try and diagnose what the problem is? I need to pull the cluster out to replace a flickering led, which started happening on the trip prior up on the cape, thought they might be related issues but the Dakota sending the 2k RPM signal successfuly seems to indicate otherwise, but maybe there's something I can look at there as well?

TIA

 

[JFF45]

I agree that if the Dakota is sending a good 2k signal that suggests the issue is more likely to be between the sender and the Dakota.
You don't really need to read frequency. The tacho signal should be at least 1 volt AC but the blinking light on the Dakota indicates whether it's getting a sufficient signal or not.

 

[mikecooper422]

likely a sender mate, there is a 2 and 3 wire version (3 wire is actually a CAS and came on Ti engines)

I would imagine you need a 2 wire job. ??

This is of course provided its not a connection/wiring issue.

 

[JRP]

likely a sender mate, there is a 2 and 3 wire version (3 wire is actually a CAS and came on Ti engines)

I would imagine you need a 2 wire job. ??

This is of course provided its not a connection/wiring issue.

I have the two wire. I tested true RMS voltage today and it seemed to be roughly in agreement with post #31 on Tacho feed on TD42

1.6V at idle

I also tested at the wires that go into the Dakota and got the same voltages, so maybe something is up with the Dakota module. I guess the fact it can produce a 2k RPM signal using the test function doesn't rule out conversion of the tacho signal into a cluster signal?

 

[mikecooper422]

Not sure on the Dakota, if the tach tests fine then I would say you could be right.

That's just a gut feeling from years of working on electric/electronic equipment.

Sometimes diagnosis has to be subbied for a bit of systematic.

If you have another sender, bolt it up and see what it does.

If no good then likely the Dakota if the integrity of the connections in the whole setup are good.