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FerrariChat.com » Technical Q&A Archives » Archive through September 04, 2002 » 90 TR Tachometer only shows 1/2 of actual RPM « Previous Next »

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Steve Magnusson (91tr)
Member
Username: 91tr

Post Number: 980
Registered: 1-2001
Posted on Friday, August 23, 2002 - 11:50 pm:   

Alex -- Although James solved his tach problem, the diagram he mentioned was related to verifying if the tachyometric relay was working correctly or not (not the tach itself). The tachyometric relay operation relies on a signal from the LH (IIRC) coil/power module (and that same signal goes to the tach) so I just passed on the previous good advice from Brian stewart that if your tach or your tachyometric relay stuff is misbehaving the first thing to do is unplug/inspect/reseat the coil/power module connections in the engine bay and my own experience that the other ignition-related connectors on the LH side in the engine bay (sort of under the expansion tank) are also in a tough place and can use an occasional touch of TLC. I don't know for sure if there's a particular line in the 4 white connectors at the bottom of the TR fusepanel that would cause your tach problem, but if you've been on the board lately you know that those 4 white connectors are a trouble-spot for TRs, and it sure wouldn't hurt IMO to unplug/inspect/reseat those as a first step if you're having an electrical problem on a TR. The (slightly incorrect :-() diagram showing the line to check in order to verify the tachyometric relay operation is in this thread:

http://server.ferrarichat.com/~ferrari/ferrarichat.com/discus/messages/112/105812.html
Alex Vivaldi (Vivaldi)
New member
Username: Vivaldi

Post Number: 20
Registered: 8-2001
Posted on Friday, August 23, 2002 - 9:28 pm:   

Can you share that JPEG with the rest of us that have similar problems. Would really appreciate it!!!
James Pai (Jaymus)
Junior Member
Username: Jaymus

Post Number: 91
Registered: 2-2001
Posted on Monday, August 19, 2002 - 1:06 pm:   

Steve Magnusson sent me a great jpeg of all the 4 connectors on the fuse board and told me the one that controls the tach. He also told me to check the connection on the coil in the back. After resetting everything and pinching the pins together, my tach is restored!

Thanks again, Steve!
Edward Gault (Irfgt)
Intermediate Member
Username: Irfgt

Post Number: 1808
Registered: 2-2001
Posted on Friday, August 16, 2002 - 8:09 am:   

It is probably in the Tach itself as the 328s have the same problem.
James Pai (Jaymus)
Junior Member
Username: Jaymus

Post Number: 89
Registered: 2-2001
Posted on Friday, August 16, 2002 - 4:42 am:   

My tach been acting up lately. It seem to only register 1/2 of the RPM on the meter. Everything is running fine, speedo is correct speed, engine is all firing on all 12.
It sometimes corrects itself showing the correct RPM, so it was intermittent for awhile. Now it only show 1/2 of what it suppose to be.

The engine revs to say 4000 rpm in 1st gear (It sounds like 4000rpm. but tach only shows 2000 or lower.

It idles at 1000 normally, but it only shows 500, so basically through all gears it shows only ~1/2 the actual rpm.

Can anyone shed some light? Is there an RPM sending unit? Like the speedo? I just replaced my speedo sending unit, now my speed is correct, but rpm is wrong.

Thanks

James

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