2001 Challenger 2000 speedometer bouncing around

[mmclean]

I know there have been many speedometer threads, but I think my symptoms are a bit different.
After running the batter flat (installed a new stereo that apparently draws a lot of current), my speedometer works intermittently - but this could be coincidental. It normally works at slow speeds (under 10mph, but not always) and fast (above 35mph, again but not always). In between, it reads zero. Sometimes it bumps and reads properly for a second or two.

Does this sound like a speedometer, sensor, or voltage issue? The wheel looks and spins good (I was wondering if there was some obstruction).

 

[Dr Honda]

It's the sender. The little paddle wheel wears, and then doesn't roll smooth.

 

[mmclean]

Do you think this is something I can temporarily fix with some lubricant to confirm? It feels smooth when I flick it (and keeps spinning).

 

[Dr Honda]

Try blowing it with some compressed air. I bet when it speeds up a little... it will vibrate, and chatter. Basically... if you can rock it back and forth on it's axle... it's going to be goofy since it won't be spinning with the flow of water.


But, if it's tight, and runs smooth... then I would check the connectors between the sender, and speedo. You could have a corroded connection somewhere.

 

[ialonso]

These tend to not match GPS speed in most cases. usually they are 5-15 miles above actual speed when going fast.

I replaced mine with a GPS Speedometer and I have been very happy with its performance and I don't depend on the paddle wheel anymore. Also it is accurate even at low speeds.

 

[mmclean]

Update on this: I replaced the wheel (but used the same axle), and it's a bit more reliable, but around 45mph, or whenever i do a sudden turn or hit a wave, it starts to jump around. I'm not sure if it's getting pushed against the side wall, stopping it from spinning. Is the there supposed to be a bushing to keep the wheel from sliding sideways on the axle? It seems to work reliably at lower speeds, so I'm a little stumped at what the issue is.

 

[drjack]

The paddle wheel needs constant contact with water flow to spin. The faster you go, or wave bouncing, etc, there's a great chance that air will be part of that water flow. Thats why slow speeds are reading stable speeds.
There should be some side play but how much is tolerable is something I'm not sure. Possibly add a stainless washer to minimize the gap.

The sensor has three wires. Two are dedicated for 12 volts and ground. The third is the pulse created by the hall effect transistor, thats generated when the N/S magnets from the paddle wheel spins pass near the transducer body.
Its not the most accurate setup, just a ball park reading can be achieved, especially when high speeds are involved. More expensive knotmeters will have calibration capabilites. The units on the Seadoo are simply general factory setup.

Possibly your stereo is messing with the 12 volt reference line?