328 tachometer

Hi Brian

This may or may not be helpful. I have not seen the problem that you are experiencing with the 328. The few that I have had to deal with either worked or they did not. Does this car still have the original ignition electronics? I just had a 246 here that was running an MSD in place of the DinoPlex and it seemed the tach was about half speed. The owner wasn't concerned, so I did not try to investigate.

I was able to have several tachs repaired at Paul's Speedometer service in California.

 

If you've got another 328 available, you might consider swapping the MicroPlex ignition ECUs as an easier first test along the lines of sowest's thought -- if the trouble doesn't go away, at least you know you've got no choice but to pull out the tach (although the alternative ain't so great either ).

 

Brian,

I experienced this many years ago on my own 328. Oddly, when the tach was "tapped" with the finger, she would then indicate the correct RPM. I purchased a new tach...and all was fine.

David

 

Does the engine sound like its reving ok? Strange thing to say I know but I had problem with my tac. Would drive along the road but tac would read may be 4k but my ears were telling me different. My problem tuned out to be a pot on the back of the tac needed cleaning with contact cleaner. Real P.I.T.A to get out... well the lights are with out breakin em to get at the screws. Then be real careful removing the bezel around the tac to get at the pot at the back. Make sure you mark the pot before you move / work a little contact cleaner in there or you will have to get it reset. good luck, loads of info on here if you seach taco.

Mark.

 

This is a very common problem with tachs on 3.2 motors. Do a search and you will find where to send it for rebuild.

Dave

 

@ RossoGTS

the tach on my 87 328GTS only reaches 2000 rpm and stays there until I slow down or stop at which time it works great below 2000 rpm??..i gotta try reseating the connection or smackin it around a bit too!

 

Mine does this some times including after I replaced the original Magneti Marelli ECU with an Electromotive system. Certainly, in my case, the problem is very likely in the tachometer and the pot would seem like the most obvious culprit, as you indicate.

 

I had the same problem this past week. Sent the tach to Hollywood Speedo for recalibrating. All fine now.

 

Yup, both Hollywood Speedometer and Palo Alto Speedometer are well versed in the repair of Ferrari 3.2 V8 motor tachometers. I forget what component in there that fails, but it is a common problem. I sent mine out to Palo Alto, and they turned it around in a week, and had it on it's way back to me. I think it was perhaps $140 or so...5 years ago.