Hey guys...I have a 1993 TBI 350 Caprice and I am having a tach problem. Yesterday I was cruising down the road at about 60 mph and the tach needle started fluttering...then it jumped down to 0 rpm's and stayed there for like 2 minutes before jumping back up to cruising rpm's. I have been told that the RPM sensor for the tach is located at the distributor? Is this correct? How would I go about diagnosing the condition? Any suggestions?

JB

 

There's no "sensor" for the tach, the tach is wired directly to the coil primary. If you're having problems with it that aren't caused by a wiring fault, then the problem is with the tach itself.

 

Ah. Dang. I guess its a good thing I got a back up cluster laying around huh?

Thanks for the reply Apeiron.

JB

 

Apparently this is similar to how the tach takes its reading off the distributor:

http://en.wikipedia.org/wiki/Hall_effect_sensor

 

Some distributors use hall-effect sensors, but that doesn't have a direct effect on the way the tach works.

 

O.K. I just found it online and wanted to post it up. I guess what I am wondering is if in the event that I needed a new cap and rotor...that the spark inside the cap may be arching and causing a weird reading. I am due for a tune up so...it has crossed my mind.

But...when I tap on the dash board...my tach jumps by me tapping my finger on the lead edge of the dash....so this indeed seems to confirm your idea that my tach in general may be going bad.

 

I had the same problem in mine, except it only did it when it was extremely cold, during the winter, as soon as the car warmed up it was fine

Kinda weird

 

Yeah man. This old Cappy has seen better days. I hope it will at least get me through for another 6 months....I'll be in a lot better shape then to decide if I want to fix this car anymore or get rid of it. Kind of sad...car has been pretty good until this last year...many many headaches.

 

Id just check the wiring, and its probably just the tach assembly. Its no biggie, I never really checked my tach anyway

Now doing a tranny swap to a th350, not doing the output shaft right to correspond with your speedo gear and having no speedometer

Thats a big deal haha.

 

Yeah...I got an extra cluster I picked up a while back. Hopefully that will solve it when the time comes.