Tach is acting strange

[FoolhardyIDI]

On Monday the tach in my truck just stopped working. I don't know what the resistance is supposed to be for the sensor. It came in at 2.33. There is wire showing at the sensor and a few broken wires in the strand. So I ordered up a new sensor. The new sensor got here today. I installed the new sensor, and it drove good for a little while and then the tach quit again. Is there some place that I should be looking that could be causing this?

 

[blakpete91]

im in the same boat

 

[OLDBULL8]

Maybe you can figure something out from these.

 

[FoolhardyIDI]

That is some great paper right there OLDBULL8. Who knew that the eec relay if for the tach. I bet that, that is my problem. Just had the other relay for the trailer & tow lights go bad. Its right next to that relay and they are both original relays.

 

[FoolhardyIDI]

I did a lot of searching and could not find an exact match for a new relay. After reading a few articles on the web I did find that part number Duralast 19840, BWD R648, ACDelco F1777A, SMP RY71T, RY71, and Wells 19840 is a correct part number despite having an extra terminal/blade on the relay. The original has a 4 blade design and the new relay has 5 blades.

 

[FoolhardyIDI]

Looks like it was the relay. But only a short drive will tell. As the tac likes to quit in about 4-6 miles of driving. Thank you OLDBULL8 for your help.
Later that day
Took the truck for about a 20 mile drive and not a hiccup with the tach. Happy to have the trans out of limp mode.