Motor Vehicle Maintenance & Repair Stack Exchange
Motor Vehicle Maintenance & Repair Stack Exchange

Questions tagged [tachometer]

20 questions
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How does the tachometer on my dashboard actually work?

Recently, I asked a question about the speedometer, how it works and how accurate it is. But that got me thinking... how does the rest of the dash actually work? I understand that the RPM measurement is a measure of the rotational speed of a…
Max Goodridge
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Connecting to the Battery During Emissions Testing to Measure RPMs?

When doing emissions testing, they connect to the battery, either directly, or using the cigarette lighter socket. I'm assuming that this is to measure the RPMs, as the only other thing connected to the car is a gas analyzer in the tail pipe. I'm…
Robert S. Barnes
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Overlay tachometer with clutch plate RPM

I've been thinking about this for manual transmissions, to ease RPM matching. Has anyone ever seen an additional dial (on the same tachometer) that shows the clutch plate RPM? In order to match RPM, one would line up the two tach…
Brydon Gibson
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Checking the motor's RPM without an in-dash tach

I'm going to be doing a carb rebuild this weekend on an 84 Ranger. The truck doesn't have a tach, but I'll be needing to read the RPMs to properly adjust the carb once its rebuilt. Is there a way of getting this information without having to install…
Kevin Evans
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Tachometer reading fluctuates at constant engine load/speed

The car in question is a 93 Miata, the tachometer needle fluctuates very randomly at random times (did it while idling and while I was driving). But the engine load does not change, it is the gauge it self that is reading incorrectly. What could…
method
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2013 Hyundai Elantra Speedometer, Odometer, Tach, and Gas gauge have stopped working

I am new to this site and found that someone has previously asked this question, but they did not indicate if they ever found a fix for the problem. Their post is here How Do Get My 2011 Hyundai Elantra Tachometer, Speedometer and Fuel Guage Display…
C Rose
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Replacing a 1985 Fiero GT Tachometer

I am working on a 85 Fiero GT which has had its tachometer go bad. I have managed find the signal wire coming from the Ignition coil producing AC voltage bottoming out a 7v while idling, increasing with the engine speed. How would I go about finding…
Tyler B. Joudrey
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Squealing and uneven idle, then tachometer drops to zero but engine keeps running

When I start my car, a belt seems to slip and then the tachometer reads zero RPM but the engine keeps running, but has weak power and only runs at low RPM. Any idea what's going on? The Symptoms: When first started, or after sitting idle and trying…
askewchan
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Tachometer Oscillating in Cold Weather

My 2012 Mazda3 appears to have some engine difficulty in cold weather (below 10F) when at operating temperature. As I hold the gas pedal steady to maintain speed, the tachometer will jump back and forth by about 100 RPM. I can feel the oscillating…
Mr. Cheezits
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How can I troubleshoot a dead tachometer in a 1998 Toyota Carolla?

My daughter bought a 1998 Carolla with a manual transmission. All the gauges work fine except the tachometer. I used a BlueDriver to get the ODB2 data and it shows the RPMs in live mode (I'm guessing the engine wouldn't run if the ECU didn't know…
Steve Hiner
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Hyundai i10 EPS error

I was driving my 2008 Hyundai i10 (1.1-litre IRDE) when suddenly the steering became very hard and the EPS warning light turned on. Later I realized that the tachometer had also conked out. I searched the internet for similar cases and discovered…
Karan
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Tachometer/Speedometer drop to zero and engine wont accelerate

today my car had the following problem: I was driving with about 80 km/h (ca. 50 mph) when suddenly my Motor didn't react to the gas-penal anymore and I wasn't able to accelerate. The tachometer and the speedometer dropped to zero, while I was still…
Yannick Huber
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Is 4000 RPM a normal rpm for a diesel school bus at 55 mph?

I have a Thomas 1991 school bus (36K gvwr) with a CAT 3116 engine and an Allison MT 643 transmission. I purchased it quite recently and when driving it on the highway, the engine RPMs are at 4000 driving at 55mph. I don't believe the transmission…
Joe B
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Why are tachometers scaled in tens of hundreds?

I live in Europe, but I think it's not really relevant. Personally I use japanese car, which always have the rev-counter scaled in thousands: 1, 2, 3, 4, 5.. However, often you can see cars with RPM scaled as 10, 20, 30, 40... Mostly VW, some…
user2461440
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How do I remove a tachometer cable from a motorcycle engine?

I am trying to remove the engine from a 1978 Yamaha XS400. The tachometer cable goes directly into the top of the engine - I'm guessing it runs off a worm gear on camshaft. There is a screw at a 90 degrees to where the cable joins the top of the…
MeltingDog
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