erratic Tach
05-08-2009, 10:24 PM
#1
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erratic Tach
Started my '84 911 for the first time in 2 weeks because of weather and business trips. The tach was OK for the first few miles and all of a sudden it was totally erratic. It went to red line and back to 0, then back to red line and then to 4K. The trip down was 70 miles and after about 50 miles it all started to be just fine. I stopped for an hour and then headed back and it started all over again. There was no correlation between tach performance and any other electrical items such as radio, A/C, wipers or lights. Before I take it to the shop on Monday I thought I would see if any of you guys had any ideas. Your input is greatly appreciated. Thanks,
05-09-2009, 12:11 AM
#2
I haddah Google dat
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That tach is not long for this world. It might be time for a refresh at one of the Speedo shops. Check out Iceman's comments on the recent Hershey thread. He found one at the swap meet I guess.
Here you go, I found it for you.
https://rennlist.com/forums/911-foru...s-stories.html
Here you go, I found it for you.
https://rennlist.com/forums/911-foru...s-stories.html
05-09-2009, 10:42 AM
#4
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Yup. Mine would just drop to nothing while driving.
Sent it out to NH speedo to be fixed, they initially sent it back & it was still doing it so they told me it was the Voltage Regulator. VR tested ok, but I changed it anyway. No dice, it was the tach all along. 2nd time, they got it right & it's been fine since.
I would imagine it COULD be a frayed wire / intermittently grounding out or something, but suspect the tach itself.
Sent it out to NH speedo to be fixed, they initially sent it back & it was still doing it so they told me it was the Voltage Regulator. VR tested ok, but I changed it anyway. No dice, it was the tach all along. 2nd time, they got it right & it's been fine since.
I would imagine it COULD be a frayed wire / intermittently grounding out or something, but suspect the tach itself.
05-10-2009, 12:14 PM
#6
Drifting
If your battery is being overcharged the CD ignition will cause the tach to be eratic and eventually the rev limiter will lock up and the only way you can restart the car is to turn the ignition completely off and back on.
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05-11-2009, 12:43 AM
#8
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Thanks for all the input. She's going to the wrench in the morning. I've had no personal time to check anything but did talk to my buddy that is the local expert on the older 911's and he promised to treat her right. I'll post verdict once I have her back. Should be Wednesday of this week.
