Tach filter/erratic/unresponsive/etc.

Doober

Moderator
Jun 2, 2003
14,704
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Catalina, AZ
www.cardomain.com
Below is the original post, but I'm hoping this will be a thread to help correct an erratic/inaccurate/unresponsive tach. From everything I've read it's a resistance value on a resistor 'pack' on the board for the tach that goes out of spec (small, white ceramic piece that looks like an IC chip). I'm hoping to fix mine, putting the details here (see page 2).
Well, seems like I'm one that needs one (others have said it's not needed). My tach isn't accurate, and I got what I almost positive (after online searches) is the tach filter from the same Monte the cluster came from. It's round with leads coming out each end (like an axial capacitor). I found a schematic for one (online here), looks like if this isn't one I'll probably just build one myself, simple enough.

If anyone else is looking for a replacement (one of the sites said GM disc. it) you can look here<i></i> (click Engine, then click Tachometer filter). These specific ones are on a Fiero store site, but I'd imagine it's the same part. If not, one of the resistors or the capacitor is probably just a different value. There's also a Corvette tach filter under the Electrical section if you prefer a Vette style one :p
 

littlboo1

Amateur Racer
Dec 21, 2006
119
1
18
Rick Nichols, Maryville Tenn
filter

i have a couple off of monte carlo ss

littlboo1
 

redneckerson

Frequent Racer
Nov 20, 2007
336
0
0
Kansas City Area
I may be having a similar issue.
On my 70 Chevelle I converted from a points distributor to an HEI, my factory tach is all jacked up now even with a tach filter. The tach will be correct for the first several minutes and then basically fall off into too few RPMs or just unresponsive.
Thoughts???
Gene
 

Doober

Moderator
Thread starter
Jun 2, 2003
14,704
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38
Catalina, AZ
www.cardomain.com
85_SS said:
Have you run completely without one (is this where you are at now)? My 84 SS tach was acting up due to the tach filter - bypassing it solved the problem.

Really? I don't currently have one and thought it might fix the problem. There weren't any v6 cars with tachs were there?
 

85_SS

Dragway Regular
Aug 13, 2004
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www.cardomain.com
Doober said:
85_SS said:
Have you run completely without one (is this where you are at now)? My 84 SS tach was acting up due to the tach filter - bypassing it solved the problem.

Really? I don't currently have one and thought it might fix the problem. There weren't any v6 cars with tachs were there?

I know Cutlass' could be had with a V6 and tach, but there was jumper that had to be positioned on the back to match. My Monte tachs do not have this, and I am not sure if a V6 Monte could come with a tach.

What problem are you having? Mine would jump around and read high before I bypassed the filter.
 

ready961

Frequent Racer
Dec 21, 2003
349
0
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Mass
Doober said:
85_SS said:
Have you run completely without one (is this where you are at now)? My 84 SS tach was acting up due to the tach filter - bypassing it solved the problem.

Really? I don't currently have one and thought it might fix the problem. There weren't any v6 cars with tachs were there?

Yes, there are v6 malibu tacs. You can usually tell by the low red line.
 

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