tachometer problem

[mickeypowa]

Hi guys,
I come back to you because my tachometer problem is still not solved.
Here is a video of my problem :

So I have wired directly the 3 bolts of the tachometer to the plug to be sur that there is no bad electrical connexion.

- The power wire is working because I have 12.7V between power wire and the ground wire
- I think the ground wire is OK because the others gauges work (more or less) and they share the same ground.
- The tach wire should be Ok because it worked 1 week ago...

So what could it be ? Is the tachometer itself dead ?
The needle still moves if I touch the part where the jumper goes (and where I have soldered a piece of copper). But it has no relation with the the speed of the engine..

Help! Thanks in advance!!

 

[kalidromos13]

Read this: Tach Fix
Maybe its just the resistor pack and all youll need to do is follow those instructions and wire in a new resistor. I had the same issue with my tach when i put it in, did this fix and now it works great!! Check it and try it out.
Edit: Just realized this is for an olds, but i believe the concept is still the same.

 

[mickeypowa]

Hi !
Thank you for your answer. I've read the link, so I have the same type of black and white chip on my tach. But it's not exactly the same, I don't know if it matters..
Here is a photo (click on it to see in full size):

So I tested the resistance between the pins :
between 1 and 8 = 4000 ohms
between 1 and 9 or 14 = unlimited
between 1 and 10 = 0 ohms
between 1 and 13 = 8500 ohms
between 1 and 11 or 12 = 7000 ohms

So according to the link you gave me I should solder a 200000 ohms resistance between pins 1 and 13 ? That's it ?

a photo of the other side of the board (I removed the copper jumper) :


Thanks
Romain

 

[kalidromos13]

Yes just solder in a 2K ohm resistor in the specified locations and that's it! Hope it works for you!

 

[mickeypowa]

the problem is that I haven't exactly the same black and white chip as in the tutorial (I guess its because I have an oldsmobile cutlass).
I guess I should solder the 200kohms resistance between pin 1 and 13 on my photo, but I'm not sure. Could someone confirm me that its good ?

 

[kalidromos13]

If you're willing to wait a few hours I have an olds tach that I'm willing to check out for you to make sure the pins are the same, but I'm lead to believe that the circuit is the same.

 

[kalidromos13]

OK I think you have it wrong, it says that r4, which is embedded in that resistor chip, loses its value over time causing the tach to read incorrectly. It also says to wire in 2 100K ohm resistors on pins 4 and 10 not pins 1 and 13. You will have to cut the leg on pin 10 to wire the resistor in parallel with the quartz crystal.

 

[mickeypowa]

thanks for your answer,
yes, I agree that in the tutorial, Its written to solder the 200k resistor between pins 4 and 10.

But I have not the same chip, as you can see on my photo, the black part of the chip links pin 1 and 13

on the contrary : on the photo of the tutorial, the black part of the chip links pins 4 and 10

so I think I must solder the pins linked by the black drawing on the chip, no ?

I don't know if I am clear in what I'm saying ahah !

 

[kalidromos13]

I understand what you are trying to say, but i don't think the drawings on the top of the resistor have anything to do with how they are internally connected? Now I'm not too sure about that, but i do know that you want to have that new resistor (200K ohms) soldered in parallel with the quartz crystal. Like i said if you're willing to wait I have an Oldsmobile Rally Gauge pod and i will confirm what pins go to the quartz.

 

[mickeypowa]

ok thanks, I will wait your check because i don't want to do mistakes !! thanks !