84 tach acting up

[hotshotzny]

the tach on my 84 has been acting stupid the past few days.... sometimes it works just fine.. others it doesnt at all....... i know the 84's had problems with the digital dash so if this is my glitch i will take it... who needs a tach in an automatic anyway

 

[CorvetteArchives]

Does the dash act normally... (test mode) when you turn on ignition to "on" (not start/run)? Both graphs should go all the way up and then down.

If its not your dash itself it may be the tack filter ...small tube with wires located next to distributor. Mine behaved erraticly jumping all over the scale while engine rpm remained constant. Good news is they now reproduce the filter.

 

[hotshotzny]

Does the dash act normally... (test mode) when you turn on ignition to "on" (not start/run)? Both graphs should go all the way up and then down.

If its not your dash itself it may be the tack filter ...small tube with wires located next to distributor. Mine behaved erraticly jumping all over the scale while engine rpm remained constant. Good news is they now reproduce the filter.

finally remembered to look at that when i got in the car last night..... everything works normally... all light up when you switch to on.. both run all the way up and back down.....

 

[CorvetteArchives]

Good! Sounds like just a connection problem.
Eventually you'll probably get around to taking the dash out and apart. When I had my dash serviced the guy added a couple wires on the board connectors inside to help prevent this problem. Most likely, if you press the dash ...not the LCD!!!... it will light up again and work temporarily. But like you said its an auto anyway!. When you do get around to taking it out its not a bad idea to run an extra dedicated ground wire as insurance from the connector. http://http://misterbill.homeip.net/vette/wiring/instrument cluster inputs_outputs.jpg

 

[hotshotzny]

not sure if this makes any difference or not but the tach is lit up and displays 0 when it isnt working.....

 

[vette079]

How is it with 84´s, is the tach filter mounted in the dash or like a 91 near the distributor.
Then you don´t have to be in the dash at all.

 

[hotshotzny]

How is it with 84´s, is the tach filter mounted in the dash or like a 91 near the distributor.
Then you don´t have to be in the dash at all.

i havent looked into it yet.... very low on the priority list....everything else works fine and like i said its an automatic fully stock so im not really concerned with watching my rpms cause im not runnin it up to red line

ever wonder though..... i have owned quite a few cars now.... mostly manuals... and very few of them had tachs.... yet every automatic has had one

 

[CorvetteArchives]

Tach filter is right near distributer as well

 

[hotshotzny]

what is this filter called so if i decide to fix it i can order it

 

[gmjunkie]

what is this filter called so if i decide to fix it i can order it

Ah lets see,Maybe they call it a Tachometer Filter!!
My guess is that you probly have a bad connection somewhere though!!

 

[hotshotzny]

almost seemed to obvious.... figured it was like the flux capasitor or something like that

 

[elkabong]

If it is flakey it could also be a grounding problem in the back of the cluster.