tachometer??

[tucsontattoo]

I have an Isspro 3000 RPM electronic tach. suddenly it just started drifting around in circles.. Any one know how to check the signal from the transducer. It appears to be mounted near a pulley on the front of the engine. (8V71 in a 4106).
Would be nice to test it at the transducer then again at the tach to see if I have an open circuit or no signal at all. If I am good in those places then the problem is in the head I'm thinking..

   If anyone has experience with these I could use some input

     Thanks TT

[wg4t50]

Two things you can do, using Digital VOM, you can read the ac voltage it produces or better would to use the frequency setting and see how stable it is.  Am assuming you do have a digital RPM display/tach.

[tucsontattoo]

 It is an electronic tach from about 1980.. Not sure if it is digital or analog (if that is possible) . I do have a digital volt ohm meter though.
how would I read frequency on a volt meter??

[tucsontattoo]

Are we talking about the readout being digital? If so no it is a needle sweep guage

[Don4107]

I just fixed mine.  It is a Datcom that has a signal generator that drives off the back of the blower.  Took it out and spun it with a drill motor and checked the AC voltage.  About 3.5 volts.  Mine had bad connections at the solderless connector spade lugs.  Whoever installed it crimped the wires on the insulation.  Fixed that and took a run today.  First time the tach has worked for the whole trip.

Good luck
Don

[wg4t50]

The analog (the type with a sweep needle) meter will work, does not have frequency ability, set meter selector to AC 5-10 volt range, start engine, read the voltage on the two wires feeding te tach.

[tucsontattoo]

I was told by the folks at AZ truck and trailer that the analog volt ohm meter measuring ohms will read like the tach in reverse, high resistance at low rpm to low at high rpm..  sound right to you guys?

Can't get to speak with tech support at Isspro, guess I am on my own as with many manufactures today, will not be buying from them if I wind up having to replace the tach.. Same goes for Iota battery chargers, all I can find for there tech support are fax numbers....nice

How do you like the Datcon tach Don?  If I have to replace this one completely end to end I will be changing brands, any advice is appreciated fellas!

[tucsontattoo]

Thanks for the help Dave and Don.. Had to run to work last night but will be searching for some sort of signal at the tach and again at the sender soon as I get a minute..
Dave, you say the voltage out put of the sensor changes with RPM and not resistance?

[wg4t50]

Yes AC Voltage is what your looking for, in the low range 5 volt Plus.

[Don4107]

Now that I have repaired the intermittent connections at the tach sending unit it seems fine.  So far the speedo is still 10% fast.  Kind of a pain to adjust the dip switches.  I have to pull the steering wheel for access to the dash the way they installed the PO installed the tach and speedo.

Don