RPM Gauge Question

I have an 80 SC coupe. My rpm gauge works, but when I change gears, it takes a while to settle down.....it moves back and forth a few times until it settles down. I think I have seen others act this way, but mine seems a bit extreme.

What do you think? Is there a fix or is this normal?

------------------
Donald Weintraub
1980 Porsche Red 911SC Coupe

Mine jumps all over the place sometimes too. I just accept it and do not worry about it.

... I wonder how accurate they really are? The jumping does not enspire confidence.

------------------
Adrian Pillow
1979 911 SC
1966 VW Microbus
PCA - Peachstate Region

Hi Donald: Mine does the exact same thing. Still need to call you to get together and talk P cars. John

I think the cause of jumping RPM gauges has something to do with your points. You might want to check your distributor. When I cleaned my points my gauges stopped jumping around.

------------------
Jeff
1976 911S

I don't believe your 80SC would have points as electronic ignition was installed at the factory. But ther is definatly a problem. The tach on my 78 is solid as a rock, as was every other tach I've ever owned. Sorry but I can't be of help in solving the problem. I guess I'm just the bearer of bad tidings.
--------------------
Paul
78SC Targa

A 'bouncing' tach can be an indicator of improper system Voltage, and failed/failing alternator or Voltage regulator. Check it with a digital multimeter, and cross-check the Voltmeter function against other known-good systems. Normal range for system Voltage is 13.2 to 14.5 Volts ... check both at idle and above 2500 rpm!
------------------
Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 03-08-2001).]

My 82 has had this symptom the whole year I have owned it. I also thought it was voltage related, and hoped one of the silver linings to my alternator ordeal would be a steady tach after shifting, but it is the same as ever. The voltages seemed in specs with both alternators. I suspect a ground somewhere or maybe something in the distributor (maybe CIS somewhere?) one of the long-term things that keeps me busy.

Olivier
82 SC

Let me define my version of jumping. The tach is steady when the engine is stedily reved up or down, normal driving. When you blip the throttle in neutral it goes from 1K to 5-6K when the actual RPM is more like 3500RPM.

I have seen this in other 911s so I think this overexcited tach is just part of the electronic ignition or tach itself.

Try to blip your throttle this weekend and see what happens.

------------------
Adrian Pillow
1979 911 SC
1966 VW Microbus
PCA - Peachstate Region

I put a msd on my 74911 and the tac didn't work. I tried all the tack adapters still did not work. So I got a auto meter tack and it worked. And the needle didn't jump and take all the time to settle down. I think it's like an enursha thing. The auto meter needle went as far as the ignition told it to do not boing! boing! boing! like the stock one did. Like when you are clearing your sparkplugs the tack looks like its going to 8000 but the speed of the needle carries it farther than than the real rpm level of the engine. A real big differince from one to another

it's internally defective. send it to north hollywood speedometer.( 818.761.513) around $100. w/MSD order their tach stabilizer.

I thought this was normal too, on my older 73S, when I blip the throttle the thing revs so fast the needle looks like it can't keep up so it bounces around a little. When I mean 'bounces around' it seems like it has a little inertia to it (laggy).

Brad

Not normal!

The tach in my '79 930 is awful, at an idle it is fine, get it over 1200 rpm's and it drops to zero. Unless I turn on my headlights and fog lights, sometimes that will work. It also bounces all over. I will be sending it in to have it fixed upon advice from my "high paid wrench". I hope it's not an electrical problem as some have mentioned.