Tachometer gauge check - RX7Club.com - Mazda RX7 Forum

3rd Generation Specific (1993-2002) 1993-2002 Discussion including performance modifications and Technical Support Sections.

Tachometer gauge check

Old 12-30-18, 03:21 PM
  #1  
Full Member
Thread Starter
 
tomatoto's Avatar
 
Join Date: Apr 2018
Location: France
Posts: 136
Thanked 8 Times in 8 Posts
Tachometer gauge check

Hey,

I encounter a problem with my Tach, it occurs sometimes right after I start the car, or after driving it for a couple minutes. When it occurs, it's actually working 'almost' normally, except that it is inaccurate, the needle pointing to a little higher rpm (like +1000rpm or so / e.g : needle pointing on 4k rpm when I'm actually at 3k rpm).
I've found many thread about the tachometer/speedo gauge fix, so I wanted to give a try to fix it.
I expected to find some leaky capacitors, but they seem pretty clean. What do you think ?




I've read in this thread that the gauge is powered via the 3 screws in the back of the gauge. I will clean those screws, and hopefully it will work better.


tomatoto is offline  
Old 01-01-19, 09:02 PM
  #2  
Full Member
 
Join Date: Apr 2018
Location: NC
Posts: 109
Thanked 1 Time in 1 Post
Following. My tach also floats and from what I’ve been told, I’m better off getting a speedhut gauge vs trying to fix it. If you find a fix, I’d love to know. I know mines off because my Apexi FC shows the RPMs.
Djseto is offline  
Old 01-02-19, 06:29 AM
  #3  
Full Member
Thread Starter
 
tomatoto's Avatar
 
Join Date: Apr 2018
Location: France
Posts: 136
Thanked 8 Times in 8 Posts
I've cleaned the screws and the small washers, and the soft circuit board with contact spray...
I should remount it in the next couple days/weeks, so I'll let you know if the problem still occurs.
tomatoto is offline  
Old 01-02-19, 06:15 PM
  #4  
Full Member
iTrader: (3)
 
Ricebox's Avatar
 
Join Date: Nov 2016
Location: Palm Beach, Florida
Posts: 182
Thanks: 0
Thanked 13 Times in 11 Posts
completely re solder that IC chip on the board there, seems to have done the trick for some people with the jumpy tach issue.
Ricebox is offline  
Old 01-07-19, 09:06 AM
  #5  
Full Member
Thread Starter
 
tomatoto's Avatar
 
Join Date: Apr 2018
Location: France
Posts: 136
Thanked 8 Times in 8 Posts
So, I test drived it but it still the same.
The more I look into it, the more I'm thinking it happens when I start the car, then after 20min or so, it gets back to normal... But I'm not sure it's always the case, it's actually pretty hard to monitor while driving ^^

Ricebox : thanks for the tip, I'll try this next time !
tomatoto is offline  
Old 01-09-19, 09:25 PM
  #6  
Full Member
iTrader: (3)
 
Ricebox's Avatar
 
Join Date: Nov 2016
Location: Palm Beach, Florida
Posts: 182
Thanks: 0
Thanked 13 Times in 11 Posts
Originally Posted by tomatoto View Post
So, I test drived it but it still the same.
The more I look into it, the more I'm thinking it happens when I start the car, then after 20min or so, it gets back to normal... But I'm not sure it's always the case, it's actually pretty hard to monitor while driving ^^

Ricebox : thanks for the tip, I'll try this next time !
mine does the same, its a very common problem. i havent taken it apart to re solder the chip on the tacho board but i'll be doing it soon.

there is alot of good information in this thread

https://www.rx7club.com/3rd-generati...1118446/page2/
Ricebox is offline  
Old 01-10-19, 05:19 AM
  #7  
Full Member
Thread Starter
 
tomatoto's Avatar
 
Join Date: Apr 2018
Location: France
Posts: 136
Thanked 8 Times in 8 Posts
thanks a lot for this topic ! Let us know if it works for you.
My problem is not very similar to the jumpy/crazy tachs I've seen on videos, mine looks steady all the time, it is just not accurate all the time... I only saw it "jump" once in months of use. Anyway, I'll try the resolder fix as well when I get some time.

By the way, anyone knows if the redline/gear change beep is still working normally when the tachometer is out of service like this ?

Last edited by tomatoto; 01-10-19 at 05:21 AM.
tomatoto is offline  
Old 01-10-19, 01:33 PM
  #8  
Senior Member
 
Join Date: May 2018
Location: South FL
Posts: 418
Thanks: 0
Thanked 7 Times in 7 Posts
Mine alarm/beep works without tach. I am not sure if it is intermittent like the tach or not though.
Testrun is offline  
Old 01-10-19, 01:58 PM
  #9  
Moderator
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 1,531
Thanked 136 Times in 123 Posts
tomatoto,

As Ricebox pointed out, there is a lot of good information in the link he provided. Page 5 of that thread discusses another member's repair to the IC chip on the tach board. Be sure to read through that section because damage to the chip and circuit board could easily happen. Please do not bypass any wiring from the instrument cluster to the tachometer from the link you provided in your 1st post. Do you have any electrical soldering skills?

Alternatively, you may post your repair journey to that thread. Meanwhile, would you please post a few photos that clearly show the solder joints of IC1 and capacitor C1?
Gen2n3 is online now  
Old 01-10-19, 07:16 PM
  #10  
Moderator
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 1,531
Thanked 136 Times in 123 Posts
Originally Posted by Testrun View Post
Mine alarm/beep works without tach. I am not sure if it is intermittent like the tach or not though.
Testrun,

What alarm/beep do you refer to? Is it the over-rev warning buzzer? What does it sound like?
Gen2n3 is online now  
Old 01-23-19, 11:17 AM
  #11  
Full Member
Thread Starter
 
tomatoto's Avatar
 
Join Date: Apr 2018
Location: France
Posts: 136
Thanked 8 Times in 8 Posts
Hi Hen2n3

Thanks for your help. I've remounted the cluster by now, but as soon as I find some time, I'll unmount it again and check closer to the IC chip and solder joints.
About the "gear change buzzer", I meant the one we hear in this video near 7400rpm :
tomatoto is offline  
Old 01-23-19, 11:47 AM
  #12  
Moderator
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 1,531
Thanked 136 Times in 123 Posts
tomatoto,

Thank you, glad to be of help. The buzzer in that video clip is known as the over-rev warning alarm. I suspect the over-rev buzzer will sound (without a tach) because it is an output from the (factory) ECU that is sent to the Body CPU.
Gen2n3 is online now  
Old 01-23-19, 01:00 PM
  #13  
RX-7 Bad Ass
iTrader: (52)
 
DaleClark's Avatar
 
Join Date: Jan 2002
Location: Pensacola, FL
Posts: 11,068
Thanked 244 Times in 209 Posts
The buzzer for the over-rev, low coolant, and low oil is in the CPU in the driver's foot well. One buzzer for all 3 items.

I think the CPU gets a tach feed and triggers the buzzer at the appropriate RPM.

Dale
DaleClark is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Hellemyr
New Member RX-7 Technical
3
08-31-09 09:45 AM
chnsx7
2nd Generation Specific (1986-1992)
2
02-29-08 10:42 AM
cloudx189
2nd Generation Specific (1986-1992)
9
07-17-07 04:44 PM
RX7Wishing
3rd Generation Specific (1993-2002)
9
11-27-04 08:23 AM


Thread Tools
Search this Thread
Quick Reply: Tachometer gauge check


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.