How in the hell do you re-calibrate the tachometer? - Third Generation F-Body Message Boards

Electronics Need help wiring something up? Thinking of adding an electrical component to your car? Need help troubleshooting that wiring glitch?

How in the hell do you re-calibrate the tachometer?

Thread Tools Search this Thread
Old 12-22-2004, 02:23 AM   #1
Senior Member
Thread Starter
Join Date: Apr 2003
Posts: 3,563
Car: 1991 RS Camaro (Jet Black)
Engine: 95 383 CI (6.3) LT1
Transmission: 95 T-56

How in the hell do you re-calibrate the tachometer?

I just scored a 90-92 145 mph speedo and installed it and the damn tach was idling at 6000. So I took the glass off and moved the needle and it idles at 1000 (grrrr). I couldn't get this sucker to stay at 800 for crap. Not only that but when I rev it seems to move double the distance. at 3200 rpm (verified through datamaster) this thing is already past 6000. How in the hell can I re-calibrate it? Thanks.
pasky is offline vBGarage Page   Reply With Quote
Old 12-22-2004, 03:27 AM   #2
Senior Member
Join Date: May 2002
Posts: 4,099

YOU can't. There are some places that will repair/recalibrate it, prices range from $85-$125.
Morley is offline vBGarage Page   Reply With Quote
Old 12-22-2004, 07:09 AM   #3
Join Date: Jun 2003
Location: Eastpointe Michigan
Posts: 254
Car: 87 IROC
Engine: mini-rammed 350
Transmission: WC T-5

I saved this thread when I bought a 6 cyl cluster ,(not knowing the difference)..It might help
I'm not to slick on posting,so try cut/paste
hope that helps
Brock's91RS is offline vBGarage Page   Reply With Quote
Old 12-22-2004, 10:46 AM   #4
Supreme Member
iTrader: (3)
BigBadLou's Avatar
Join Date: Jul 2004
Posts: 2,989
Car: '91 Z28 convertible
Engine: TPI
Transmission: T5
Axle/Gears: 3.27 posi disc

That thread is about the older tachs. The newer 90-92 instrument cluster has different gauges and uses a bit different technology.

The tach is calibrated by precision cut resistor module that's soldered onto the driver module board in the instrument cluster box right below the tach.

It is not easy to adjust but if one has access to the right equipment (Fgen, meters, scope, parts), it's not impossible. I myself am thinking about adjusting mine (got sold a dud that shows way off) but can't find the time. If I succeed, I might offer this service to fellow 3rdgenners.

Hope this helps.
BigBadLou is offline vBGarage Page   Reply With Quote
Old 12-23-2004, 03:45 PM   #5
Senior Member
Join Date: Oct 2002
Location: Edmonton AB Canada
Posts: 386
Car: 86 Firebird
Engine: 355 4 bbl
Transmission: TKO 600
Axle/Gears: 3.73 L/S

Bad Capacitors?

I think it is likely that a capacitor has gone out of tolerance like the specified link talks about replacing. If you're handy with a soldering iron it would be quite cheap to replace all the capacitors on the circuit board with new ones.

Certain capacitors lose their value over time and this could easily cause the tach to go way off.
Rustydawg is offline vBGarage Page   Reply With Quote
Old 12-23-2004, 10:32 PM   #6
Supreme Member
iTrader: (1)
DENN_SHAH's Avatar
Join Date: May 2004
Location: houston
Posts: 2,247
Car: 83 POS monte carlo
Engine: 92 5.7 tpi
Transmission: 700r4
Axle/Gears: 2.42

pasky, does the tach board you have look like the 1 from the other thread or this 1?
Attached Thumbnails
How in the hell do you re-calibrate the tachometer?-tachboard.gif  
DENN_SHAH is offline vBGarage Page   Reply With Quote
Old 12-27-2004, 01:57 PM   #7
Senior Member
Join Date: Jul 2003
Location: Detroit, MI, USA
Posts: 509
Car: '82 Trans Am
Engine: Blown 540 BBC
Transmission: TH475
Axle/Gears: Dana 60, 4.10 w/spool

I have a friend that works in an instrumentation/calibration lab where I work verify the accuracy of my factory tach (also had him do some other tachs I have). Basically you just hook the tach up to a piece of equipment called a signal (frequency, pulse) generator, determine your pulses per rev, and set the machine at a specific rpm, and verify if the tach is reading the same. We did mine in 200 rpm increments, and it was amazingly accurate up to 6000 rpm - after that, it read about 200 rpm low up through 7000. Since it was overall pretty close, I decided not to try and recal it.
Motor City Mike is offline vBGarage Page   Reply With Quote
Old 12-31-2004, 08:32 PM   #8
Senior Member
Join Date: Apr 2003
Location: Albany GA
Posts: 582
Car: '90 RS Vert
Engine: 305 TBI
Transmission: 700-R4

Try This

I work on electronic equipment at work a lot. I have not experienced the problem you describe but I would suggest that the first thing you should probably do is be dang sure that the contacts on both the cluster and the car are clean. What you describe could be the result of the tach getting erroneous signals through bad contact... Sometimes those contacts look clean but there is some accumulation of oil.dust etc that is just bad enough to cause a poor contact.

Worth a try before you spend any money...

Speedgraphic is offline vBGarage Page   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
Was I too Optimistic ? TPI L98 Power FormulasOnly TPI 54 02-07-2016 06:01 PM
Just wanted to say thanks Rocket-Doc TBI 1 11-14-2015 03:08 PM
Sputter on acceleration 92camaro350cci TBI 8 10-14-2015 10:29 AM
Water leak above pedals... ideas? aaron7 Interior 1 09-30-2015 10:15 AM
Morel hydraulic race lifters: new design = tappity tap tap tap? dimented24x7 Tech / General Engine 4 09-06-2015 04:51 PM

Go Back   Third Generation F-Body Message Boards >

86, calibrate, calibrating, calibration, camaro, carlo, electronic, electronics, jet, monte, rpms, speedo, tach, tachometer, tachometers, technology

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 03:09 PM.

All content copyright 1997 - 2014 All rights reserved. No part of this website may be reproduced without the expressed, documented, and written consent of's Administrators.