Tachometer Woes

[lerxst]

I must admit I'm now officially bitter. Here's the scenario:

Since I got my 1990 Talon Tsi AWD, the Tach never worked. Except ONCE. It was really rainy, and it started fluttering, worked solidly for a bit, then stopped. That was over 2 years ago.

Since then, My theory is that water was shorting the empty plug where the Tach Noise Filter is/was supposed to be, since after reading a lot of FAQ and diagrams, I've noticed it missing.

Here's what I've done in the last week:

Cut the Tacho Noise Filter connector and twisted all three wires together bypassing the filter altogether. Soldered, Heat shrunk, Taped, replaced. I like solid connections and weather sealing.

Removed the coil pack, verified that all wires from the coils and to the Tacho Interface are good. Applied terminal grease when refitting the wires after cleaning the terminals. Did the same with the 4pin output connector.

No go.

Removed the coil pack again, and ran a complete new set of 4 wires from the first coil, second coil, ground, and interface output. Cut the wiring harness on the car and put a brand new "very nice" 4 pin connector on the harness, and it's mate to the 4 brand new wires I ran from the coil pack.

Car runs, but still no tacho.

So, What are my options at this point? Should I start looking at the Tacho Interface? Is there a way to test it? Should I start looking behind the instrument cluster? Are there ways of looking for the Tacho signal there, or perhaps a way to simulate a Tacho Interface pulse to verify that the gauge works?

I'm stumped and grumpy...

-jre

 

[LAUNCHED]

Was the gauge cluster ever switched? The 90 ones are specific for that year and later ones will not work. If you are stumped and don't want to mess with it, just buy a after market tach and put that in.

CRAIG

 

[lerxst]

To my knowledge, it's the original cluster. Remember, it did work once when it was rainy, so I expect to find an intermittent more than anything at this point.

I have an extra tachometer element from a '90 laser cluster that I am going to (hopefully) try tomorrow. Here's hoping that the element in the cluster is the issue...

-jre

 

[lerxst]

AHA!


I spent today re-tracing everything. After all looked good, I cracked the console open.
I removed the tachometer movement, and remembered the kid I got the car from saying something about switching the dial faces. I compared the tacho movement to the extra that was in the box of parts (other meters, etc... I think he got a complete new console) and noticed that they differed.

I replaced the movement with the older-looking one... voila!

As for why it worked for a bit during the rain, I've no idea!

But... tacho!!!!!!!!!!!!

THanks for the advice / help all...

-jre

 

[Defiant]

AHA!


I spent today re-tracing everything. After all looked good, I cracked the console open.
I removed the tachometer movement, and remembered the kid I got the car from saying something about switching the dial faces.

Ah, and yet again, four days later, we get another clue for our little Two-Minute Mystery.

Y'know, it's really tough to figure out why your shoes might be melting if you won't tell us you're standing on magma.

Congratulations on your fix.

 

[ADrewzki]

Since his problem was fixed, I was gonna ask where the signal to the tach is provided on the cluster. My tach hasn't worked since I got the car as well and I've tried one that was proven to work in it. Funny thing is that my HKS turbo timer reads rpms just fine so it's probably a problem in the wiring or the actual connection on the back of my instrument cluster. I've read on vfaq that the tach signal is provided to pin 6. I should be able to check voltage from Pin 6 to ground and get a reading proportional to rpm, right?

 

[btracer]

*edit*

sorry, posted in wrong thread some how

 

[lerxst]

Since his problem was fixed, I was gonna ask where the signal to the tach is provided on the cluster. My tach hasn't worked since I got the car as well and I've tried one that was proven to work in it. Funny thing is that my HKS turbo timer reads rpms just fine so it's probably a problem in the wiring or the actual connection on the back of my instrument cluster. I've read on vfaq that the tach signal is provided to pin 6. I should be able to check voltage from Pin 6 to ground and get a reading proportional to rpm, right?

I think you'd be looking at a PULSE not an increasing voltage.

The problem I had is that I had no idea someone switched the tacho movements before I got the car... and didn't know it'd matter...

Once I started comparing schematics, and from hints from people here, I decided to check.

-jre

 

[ADrewzki]

I think you'd be looking at a PULSE not an increasing voltage.

The problem I had is that I had no idea someone switched the tacho movements before I got the car... and didn't know it'd matter...

Once I started comparing schematics, and from hints from people here, I decided to check.

-jre

Hm....a pulse might be a little more difficult to measure with a multimeter. Thanks tho.