Can someone explain to me how they work? I fixed my KDP this weekend and when I got everything back together my tach isn't working. Checked the wire from the alternator, it was corroded, so I stripped and reconnected it, but still nothing. It was working fine before I did the KDP.

Tach is an older Isspro.

 

I believe the Isspros get their signal from the crank damper. Should be a sensor and a couple magnets. Might check the sensor adjustments.

 

When I removed the damper there was no pickup anywhere near it. Also, no magnets on the damper (a lot of built up crud, though). Anybody got a picture of what the pickup looks like?

Oops.. It's not an Isspro, it's a VDO 6000 RPM tach.

 

The wife's truck came with a VDO tachometer that IS wired into the alternator; I have no idea how.


I have an old Autometer/Autogage that has a sensor that is hose-clamped onto the outside of the alternator; I am curious if this type of tach can be internally wired.

 

also have an autometer w pickup on alternator case. tried a shift lt on it. both wires. neither worked. very sad. don't know what they're using for a signal.
any ideas? tc

 

The tachs that work off the alternator count the poles as they go go by.
When the alternator is working the windings produce a magnetic field that the pick up senses and send to the tach.
There is another kind that you have to open the back of the alternator - not the whole alternator - to gain access to a 'W' screw. It kind of picked up it's name from the VW diesel tach that used the alternator also.

I don't remember which forum - but one of the Cummins forums - has a 'how-to' on running the wire for the alternator.

Neither produces enough signal for a gasser tach but IssPro and AutoMeter diesel tachs both use one of these methods.

check this :
http://www.cumminsforum.com/forum/89...lternator+tach
Post # 3

This is a link to a full article - - if anyone's a member of TDR
http://www.turbodieselregister.com/f...d.php?t=132600

OH - one more thing --
Just a bout ALL the posts I read about using the alternator pick up that straps to the outside of the alternator say the pick up HAS to be pretty close to 8:00 to get the most reliable reading.

 

I just checked and the 12v wire is only getting about 3 volts, so there must be a break or short in the wire somewhere. Gonna have to chase that down tonight.

 

Thank you.

Best I remember, mine is on about quarter-til-11; maybe relocating it to 8-o-clock will get rid of that low-speed idle innaccuracy.

At idle, the needle shows about 700; but, turn on the A/C and it starts jumping around between 1000 and 1500, until I depress the accelerator the least bit, which makes it settle down and read like it should.


I am assuming 8-o-clock would be standing in front of the truck, looking at the alternator mounted on the engine from the forward end.

 

It turned out to be a faulty power lead. Re-wired it and it's working now.