Any way to fix non working Tachometer?

[convx4]

I have replace my computer in my 89 dakota and now the tachometer wont work.

Is there a way to get it working again?

[Force Fed Mopar]

There's usually a little circuit board on the back of the clusters that snaps on and off. Not really related to a computer swap but it's possible it coincidentally is acting up. The have issues with bad solder joints, can be reflowed.

[convx4]

If I change computers the tach will work. Any way to get the circuit board wired and get a working tach.

[Force Fed Mopar]

Hmm, maybe that computer doesn't have a tach output...

[sdac guy]

What is wrong with the computer that operates the tach correctly?

Inside the housing is two boards, a logic board and a power board. The tach works off a signal from the logic board. If the problem with the computer is something with the power board (engine electrical, charging, ignition, fuel injectors, etc) then you can open both computers and just change the power board between the two.

The power board just sits on top of the logic board and is the one with the 14 way connector.

Barry

[convx4]

The original computer that operates the tach properly had the idle circuit malfunction. I was able to get a chip from BoostButton but the SEMC I installed it into didn't have a tach. I thought that the cal controlled the tach but it seams the board also has some thing to do with it.

I would think that a stand alone wiring solution could get my tach operating properly.

[sdac guy]

Bummer.

I think your only solution will be to find a computer from a vehicle that had a factory tach in it.

Barry

[convx4]

I would like to try too wire the factory dash tach as a stand alone unit.
It would be easier than finding another computer
Anyone got some helpful advice?

[chromguy]

I would like to try too wire the factory dash tach as a stand alone unit.
It would be easier than finding another computer
Anyone got some helpful advice?

This is possible but I agree with Barry....it will be much easier to get another SMEC that operates your tach. Even if one has tons of experience with electronics it will take many tens of hours of wiring/prototyping/troubleshooting.
For example, since your SMEC does not appear to output a tach signal, now you need to decide how you are going to get a tach signal. So you in theory could:
1)hack into the HEP circuit, count the pulses, convert the pulses to RPM and fiddle around to determine the correct voltage to drive your Tach.
2)use a system such as MPSciLink with MPScan to monitor the RPMs from the ECU on the diagonstic port. Add a bit of electronic magic for the correct voltage.
3)connect up a crank pickup signal, and convert it somehow to a voltage that that works with the tach
4)or buy another SMEC that has a tach output

While ideas one to three sound fun, none are easier than four.
Sorry this may not be helpful but......

[83scamp]

Another easy one is buy an aftermarket tach, and mount it on the dash(or replace the factory unit with one). They pull the signal from the coil. You can have one hooked up in less than an hour.

I believe the real issue here is, the factory tachs don't use the coil signal, like an aftermarket tach does. It has a unique signal from the SMEC.

[convx4]

Thanks for the reply's. Too bad it was not an easy fix.