 What is happing to my tach?, TAch drops out at about 4500 rpm Also drops if I use directional swithch. Then bounces all over |
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| moneysmarts |
 May 11 2026, 09:48 AM
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#1
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Member  Group: Members Posts: 174 Joined: 2-March 04 From: Central Massachusetts Member No.: 1,745 Region Association: None 
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What's going on here? I've had the same set up for 20 years (2.0 D-Jet with MSD 66AL)
Now at 4500 rpm the tack drops out, then bounces wildly. Also if I use the directional signals, the tack drops. Ill try to add a little video |
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| moneysmarts |
May 11 2026, 09:49 AM
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#2
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Member Group: Members Posts: 174 Joined: 2-March 04 From: Central Massachusetts Member No.: 1,745 Region Association: None
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Hmmm
Video wont upsoad |
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| IronHillRestorations |
May 11 2026, 10:01 AM
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#3
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I. I. R. C. Group: Members Posts: 6,938 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None
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Try changing the points
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| moneysmarts |
May 11 2026, 10:08 AM
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#4
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Member Group: Members Posts: 174 Joined: 2-March 04 From: Central Massachusetts Member No.: 1,745 Region Association: None
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QUOTE(IronHillRestorations @ May 11 2026, 08:01 AM)  Try changing the points Thank you. I will try that. Since I've owned the car (25 years +) I have never gapped the points. I thinks Slits told me they were useless with the MSD, and to just leave them alone. |
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| moneysmarts |
May 13 2026, 02:41 PM
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#5
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Member Group: Members Posts: 174 Joined: 2-March 04 From: Central Massachusetts Member No.: 1,745 Region Association: None
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Well. I have a nice clean dizzy with new points and condenser, but my tach still drops to zero and bounces back up and down at high revs. Smooth and steady from 1000 to 4500, then, boom. falls right off as the car is still reving higher.
I also noticed that at any RPM, if i use my directionals, the tack also freaks out. Almost like some electrical gremlin. I think all my grounds are good. Maybe I have bad bulbs that are causing feedback?? open to any recomendations |
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| Spoke |
May 13 2026, 03:41 PM
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#6
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Jerry Group: Members Posts: 7,390 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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QUOTE(moneysmarts @ May 13 2026, 04:41 PM) I also noticed that at any RPM, if i use my directionals, the tack also freaks out. These 2 electrical systems should be isolated from each other. Sounds like you've lost the ground on the tach or some other wiring issue. |
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| porschetub |
May 13 2026, 03:58 PM
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#7
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914 Guru Group: Members Posts: 5,105 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
QUOTE(moneysmarts @ May 14 2026, 08:41 AM) Well. I have a nice clean dizzy with new points and condenser, but my tach still drops to zero and bounces back up and down at high revs. Smooth and steady from 1000 to 4500, then, boom. falls right off as the car is still reving higher. I also noticed that at any RPM, if i use my directionals, the tack also freaks out. Almost like some electrical gremlin. I think all my grounds are good. Maybe I have bad bulbs that are causing feedback?? open to any recomendations Is your tach to coil wire in good condition/ connection ?, it seems to me the tach may have a poor earth or worst of all the tach is failing which due to age (ask me how I know ) my 911 tach pretty much did what yours is doing before total failuure . Worth checking all the wiring and maybe try a secondary tach to body ground wire and see what you achieve ? ,good luck cheers. |
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| moneysmarts |
May 13 2026, 04:38 PM
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#8
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Member Group: Members Posts: 174 Joined: 2-March 04 From: Central Massachusetts Member No.: 1,745 Region Association: None
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Thank you
Is there a wire that runs from the tach through the tunnel directly to the coil? |
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2 Members: moneysmarts, Spoke
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