tach jumping all around

[BIGSIX]

Just like the subject says, what would cause this? The tach was working great until yesterday (great meaning....not accurate)
I have a scanmaster, so I know the tach has know clue, the car runs great

Any ideas, the coil pack and module are pretty old and crusty looking. Thanks

Travis

 

[turbo buicks]

do you have the stock tach? if so they are like the stock boost guage...notoriously crappy and break after awhile. according to my stock tach i turn 6K+ rpm @ idle and at 10 vacuum i make a whopping 17 psi!

 

[BIGSIX]

Great

I was just wondering if a specific problem could cause the tach to freak out?????

Later

Travis

 

[turbo buicks]

i dont know what causes them to go bad, maybe a sensor or something.

 

[BIGSIX]

Come on!!!!

I cannot have the only TR with the tach that jumps around.

Anybody else!!!

Travis

 

[Turbo Brian]

My tach jumps around too, when cold. The problem started when we pulled the dash cluster during troubleshooting when the car would not charge. I have since installed a different cluster to check the tach and the problem persists, leaving me to believe that the pins at the dash cluster connecter are not properly seated when the car is cold.

 

[hot6-231]

Re: Come on!!!!

Originally posted by BIGSIX
I cannot have the only TR with the tach that jumps around.

Anybody else!!!

Travis

Had this same exact problem............Turned out the wire leading into my "hot" connection in the fuse box was loose. Might give that a try! Hope this helps............KB

 

[rick j.]

I had a similar problem a few years back. The tach started jumping and reading incorrectly. Finally, one night the car quit and rolled to a stop. No SES light but the interior lights worked. I unscrewed the under dash panel and found a thick red wire by the steering column that had green corrosion on it. Turns out the wire was hanging on by a thread, and eventually broke. I'm not an electrical guru, but I am assuming that it went to the ECM somehow. Anyway, I snipped the ends, spliced it, and I haven't had the same problem since. Don't know if this is your problem, but it was mine. Good Luck.

 

[GNVenom]

One of the biggest problems with the tach and boost module is the degradation of these two IC's:

http://www.casperselectronics.com/c...cgi?search_request_button=yes&keywords=103070

They deal with calibration of each of the sections in the boost/tach module. We have them available from stock and once they're gone - they're GONE. Last of the production parts! You need to be able to desolder and replace the chips. We can do it too, if you don't have the capability. Remember, these are unique to the turbo Regal and GN ONLY.
-John Spina
http://www.casperselectronics.com

 

[BIGSIX]

Thanks

Thanks for the info, I will check it out this weekend.....

Travis

 

[GNVAIR]

I just found out that an inoperative tach can be the circuitry inside the module. I installed an after market control module on the Monte and the tach stopped working. I installed the one from my GN and it worked fine. Keep this in mind as well if the other things dont solve it.

 

[GNVenom]

That is an interesting scenario. I have found quite a few problems with the 'aftermarket' CCCI modules, many of which will not even test with our CCCI Simulator. That's odd, since it would seem that the aftermarket part would've been designed to exactly replace the AC Delco unit. So, this is why I always recommend the OEM replacement part instead of aftermarket. I'm gonna put a new post up regarding this problem, and see if anyonel else has had this happen.
The boost/tach module accuracy problem: We have seen a number of them with all of the same problems - which led us to purchase these IC's to repair them. It seems the problem is showing itself quite frequently now since the age of our GN's is a factor. We've seen this same type of problem with the digital dash cars where they all seem to exhibit a peculiar problem as they age.
We'll keep you posted,
John Spina
http://www.casperselectronics.com
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