Tach question

[Saskredneck]

So with a major coolant leak into the oil most likely a head gasket on my 86 4x4 project I stole the instrument cluster and tach sensor out of it for my 86 2wd instead of waiting for the snow to melt to get to the junk yards and grab them. Since the 4x4 has some major wiring issues I was hoping that was the reason it was jumpy and wouldn't read a steady rpm, so I installed it into the 2wd and it's performing the same. I checked the wiring on my truck and the problem isn't the wires from the cluster to the quick connect for the tach sensor. So is there a way to test the sensor its self? A lot of sensors in the new diesels in construction equipment I fix for a living have a tolerable ohm range for most sensors can these be tested the same way?

 

[79jasper]

Yes, but i couldn't tell you the values.


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[ifrythings]

The way I test these types of sensors is I take them out, hook up my meter and put it on a low volts AC and put the sensor end up against one of the "old school" power adapters for electronics, its the heavy ones, not the newer cell phone chargers. These sensors are either working or dead, there just a bunch of wire wrapped around ferrite core so nothing to go wrong unless the wire breaks which will cause you to get nothing out of it.

 

[theguruat12]

Personal guess would be either a bad tach head, or just a dry tach head (hit the shaft with some graphite oil). As previously states, the sensours pretty much are either good or bad, no real in-between.

In any case, the values are 2k-3k Ohms.

http://www.oilburners.net/forums/showthread.php?59468-Tach-Sensor-testing

 

[Saskredneck]

Tested the sensor at work and sure enough it's done for, have to wait till payday to grab one next week. Sucks finally getting a tach in the daily driver and it is useless till Tuesday.