Tach is acting weird

[subaru_terrence]

I noticed my problem recently in my BE....
every once in a while, the tach needle will rev up and down itself but there's nothing wrong with my car.
According to my scangauge, everything is fine including the rpm. It's the tach needle that is acting weird.

does anyone know what problem could it be? Do I have to replace the actual cluster?

[chuckthefuk]

Is the engine rpm accurate to the tach? When it jumps up a few rpms does the engine sound like its reving? If so you may want to check your IACV (idle control valve)

If not take the tach apart and re-seat it and clean the connectors.

OBDII diagnostics never picks up sketchy idle control valve issues. 100%!!

- Chuck

[subaru_terrence]

the engine idles just fine...
there is nothing wrong with the engine....just the tach only

[chuckthefuk]

0) How many electronics have you added. Sometimes ground noise / interference play around with your tach.
1) Clean the connectors on the back of the tach and the harness itself.
2) Reset your ECU. pull the ground off step on the brake pedal and play with your accessories for a few minutes. Then plug it back in.
3) You VSS sensor could be the problem giving your tach strange readings. I think VSS controls tach at least.
4) If not take the tach apart and re-seat it and clean the connectors.
5) Try a different tach.

Good luck
-Chuck

[subaru_terrence]

prior to the tach problem.... i added 1 more amp to my system recently so now i am running 2 amps and 1 sub
I guess it might be the amp that interference with the tach?

[chuckthefuk]

I was more specific to the front/cab of the car not the trunk. It is possible that your ground wire is not properly grounded (attached to the chassis)

Try to disconnect the entire sound system (main power wire) or unplug the remote 5-volt from your deck. Check your tach. If its fine then you got interference.

-Chuck

[ouch1011]

AC interference will mess with the tach. I've actually seen a failing alternator leaking AC voltage and cause an engine misfire (which also caused the tach to jump around a lot because the AC voltage was causing the ignition system to fire erratically)

BTW, AC=Alternating Current, A/C=Air conditioning...just so nobody gets lost in translation.

[LIMITED]

Check your battery.
my whole cluster died on my BE, a day later the battery died.

[subaru_terrence]

voltage is fine with my battery so far....the tach is acting normal these 2 days as well