So sorry to bother ya w/such a stoopid question. But I’m an ASE Matster and CANNOT find it online ANYWHERE. Diesel alt’s have a seperate tach wire that reads only a select # of fields in the alt AND that is where the signal it sent to the tach through AN INDEPENDENT wire. What am I supposed to get a s a reading out of it to verify its working. I assume It’s an AC signal. Please help. Tankz Larry B.
That’s right. The signal is received from the AC output on the alternator. So it is safe to assume it would be an AC signal. The wire is usually marked on the alternator in one of a variety of ways: AC, AUX, S, R, TACH or nothing at all. Generally hooking up a known GOOD tachometer will insure correct operation. But that isn’t what you wanted to know. So I did some digging and came up with the following.
Tachometer Troubleshooting
How to check for the presence of a signal on the signal terminal
If you know you have good battery positive supplied. Measure the signal between the signal and ground terminals. This should read in excess of 2 volts DC.
If power and signal are present, then it is possible that the tractor tachometer is damaged.