The tach in my 94 idi only works when you start it up. Then it stops working. Replace tach sensor. Any other advice, or to try next?

 

Case IH Guy, Welcome to the IDI forum. As you have changed the sensor, check the wiring harness for any chaffed wires. I has been reported just unpluging the harness from the back of the gauge cluster, and plugging it back in will sometimes cure the no tach issue.

 

Farmert, while you are right, these Tach sensors can be bad from the factory, or they will work forever. I would take the tach sensor out of the oil filler neck/ip gear cover and clean it, these tachs are magnetic and will attract shavings and whatnot....

 

I am not trying to hijack thread, but I am having similar problem, could you explain a little better about the oil filler neck/ip gear location of the tach sensor, I want to try cleaning mine up to see if it will work all the time, not some of the time.

 

it'll be the big threaded plug looking thing on the IP gear housing, to the right of the oil filler neck with two wires comming out of it

 

AHA!,Found it. Thanks, I will post my results when I get a chance.

 

the part where the wire comes through the firewall can have a bad connection, and the gauge can also have a bad ground -

I have both going on, push clutch in and sometimes it stops working or only halfwayish. Also hit the lights and it changes about 100rpm.

 

It can also be your alternator messing with it, i know I dont have one in the 84 motor i just swapped in and the wires will pick up the pulses from your alt....

 

I took the sensor out and cleaned it up with no results. It still only works at high rpms, 2000 or more. Oh well, the "beastie" makes enough noise when idling I know it is still running.

 

The truck that this is happening too is an auto, I got the truck and the front axle just got replaced so I haven't drove it yet. Will this effect the shifting with it not picking the tach sensor? FYI, I have the stuff to switch to a manual.

 

The 94 should have the E4OD tranny, so yes it will effect how the tranny shifts. I'm not an auto guy, but I believe it will through the tranny into limp mode, and it will kill the tranny if you drive it much without getting it fixed.

 

Yes, a bad tach signal will cause the computer on an E4OD truck to lose it's mind...

 

The truck isn't a daily drive. So it will sit till its fixed. Plus I'm making a new harness for the glow plugs too. The manual is what I'm wanting just don't have the time for the swap. Work has got me swamped at this point (love my job, it comes first). So hopefully I won't have to work Sunday and I'll be able to work it on.

This will be me fourth zf 5speed truck when the tranny swap is done. And my 3rd diesel. First 6.9 idi banks turbo, 94 PSD, now 94 idit. I'm excited to get this truck going. My First crew cab.

 

If the sensor is bad it will effect the trans shifting, if the tach in the dash is bad it shouldnt bother the trans at all. take it for a drive and if it shifts bad you know its not the gauge, if it shifts fine, you know the tach pick-up is good....

Diesel Rod

 

I had a problem with my sender. Tach worked sometimes was erratic others. Seemed to be wet weather triggered. Turned out to be wires were they went into sender had bad insulation. I used some liquid eletrical tape at the entrance to sensor and have not had a problem since.