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Need Speedo Help, 1998 Sunsetter Lx


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Hi Guys, I'm hoping you can help me a out with some speedometer issues.

Here are the symptoms:

When starting the boat, the left speedo goes through it's whole cycle (zero to full speed, then drops back down), it then pegs itself at 50 mph once the motor is all the way started.

The right speedo kind of jiggles up and down, but never high then 10 mph, then when the engine is started it never comes up above zero.

Where do I go from here? All of my other guages work great.

Here's what I've done so far:

I've cleaned the pitot pickups (the left was clogged, the right one is broken!), and taken the lines off at the dash and blown then out. I did not get any water out of them, or find any in them.

Thanks in advance for all your help.

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Hi Guys, I'm hoping you can help me a out with some speedometer issues.

Here are the symptoms:

When starting the boat, the left speedo goes through it's whole cycle (zero to full speed, then drops back down), it then pegs itself at 50 mph once the motor is all the way started.

The right speedo kind of jiggles up and down, but never high then 10 mph, then when the engine is started it never comes up above zero.

Where do I go from here? All of my other gauges work great.

Here's what I've done so far:

I've cleaned the pitot pickups (the left was clogged, the right one is broken!), and taken the lines off at the dash and blown then out. I did not get any water out of them, or find any in them.

Thanks in advance for all your help.

That is about the weirdest thing I've heard on this forum. Your symptoms would suggest the dash gauges are electronic while your pickups are mechanical. I would snoop around the brass tubes on each side of your gas tank, maybe there is a sending unit somehow wired to them.

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The guages are electric. I forgot to mention that I pulled the dash plate (or whatever you want to call the wood trim looking piece your guages mount in) to see if I had any loose connections. There is a 3 wire plug going into each speedo guage.

The pitot tubes under the dash connect to the mdc which turns that air pressure into an electric signal that controls the guages.

I'm not sure if I have any brass tubes (unless everyone has them and I just can't see them). I pulled the cover off the gas tank, and can see the lines drop down below it, but don't see any brass tubes.

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Ok, so I pulled the dash again this morning to check my connections, everything is good.

To clarify my symptoms, when I turn the key on, all the guages twitch then go to their level (example, fuel goes to half a tank). The left speedo then jumps to full speed! While the right stays at zero.

I pulled the three wire plugs off of the back of the speedo (the appear to be the same on all the guages, even the wire colors are the same) and swapped them, there was no change left to right. I then pulled a plug off of the water temp and plugged it in to the left speedo, it still pegged out full speed. I disconected the pitot tubes and gently blew a little air in the direction of the mdc pitot connections, and there was no movement of the speedo guages.

Any other ideas?

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Seems like you've done most of the troubleshooting & your MDC or gauges are the two issues.

The MDC converts the various analog signals from the boat into digital signals that are sent to all the gauges on the same wires (seems you know that). Not sure if the signals for the speedos are differentiated right & left, but would guess that they are. My '01 has only one speedo, with a selector switch for which pitot is used.

Since the gauges all initialize correctly, and you didn't get any movement when you blew into the pitot connections, I'd guess that the MDC is the issue. IIRC - you can find them for around $230 - 240 at a few sites - including Bakes as well as others.

One thing you may want to try is to disconnect your lanyard while the key is on & gauges are initialized, then reconnect it & restart. I've had that reset a non-functioning tach/speedo in my '01.

If you have brass tubes, they should be run vertically inside the transom - very close to your pitots. Since you cleared the pitots from the dash area, the brass tubes shouldn't be the issue.

Edit: You can give the guys at Bakes a call, other have said that they are very helpful & willing to troubleshoot over the phone with you.

Edited by wienrdog
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Here's a weird thing, my lanyard switch does not need a lanyard on it for the boat to run. I looked behind the dash, and there are 4 prongs on the lanyard switch, only two of which have any clips / wires on them.

If I pull a line off of the lanyard, the guages shut off, and when I put it back on, they restart and go back to their above mentioned positions. Likewise, I pushed the lanyard button in, with both wires connected, and the guages shut off. To get them to turn back on, I had to pull of one of the wires and push it back on, and when I did so the guages jumped back up to their positions mentioned above.

Thanks for the advise, the search goes on!

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Sounds like somebody switched the wires on the back of the lanyard. One pair of pins is connected with the clip on (button in), the other pair is connected with the clip off (button out). Some run their switches like that as the lanyard switches have been known to fail or the clip doesn't push the button in quite far enough. They can still use it to kill the engine by pushing in on the lanyard switch, if you're in the boat... I'm not a particular fan of that modification other than as an emergency fix.

It does sound like something has gone awry in the MDC and the speedo circuits are damaged... Best of luck with your trouble shooting... Let us know what you discover.

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  • 2 weeks later...

I have a similar problem with my 2002 Sportster.

First of all, the wires on the back of the gauges are not analog, they are ModBus communications, this is typical in the auto industry. You can move the gauges around and it doesn't matter.

Does anyone know if the speedometer is supposed to go to full up when first powered up for gauges that are electronic?

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The guages are electric. I forgot to mention that I pulled the dash plate (or whatever you want to call the wood trim looking piece your guages mount in) to see if I had any loose connections. There is a 3 wire plug going into each speedo guage.

The pitot tubes under the dash connect to the mdc which turns that air pressure into an electric signal that controls the guages.

I'm not sure if I have any brass tubes (unless everyone has them and I just can't see them). I pulled the cover off the gas tank, and can see the lines drop down below it, but don't see any brass tubes.

they are on the starboard side in the very back just forward of the gas filler tube. you probably have a breach in the lines somewhere. did you have a tower installed?

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Yes, I do have a tower. I'll check the lines again, but I believe (I had my wife checking) that air came out of the pitot tubes in the back when blown from under the dash.

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Yes, I do have a tower. I'll check the lines again, but I believe (I had my wife checking) that air came out of the pitot tubes in the back when blown from under the dash.

Are thy Airguide speedos?

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Airguide, no paddle wheel. I don't have any signs of water under the dash that others have described shorting out their computer; all my other guages work correctly.

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Just to add, I made a mistake earlier, the gauge does not go full until after is "initializes" (as in jiggles around). At that point, the one gauge goes to full speed, and the other to zero. Sorry about the mistake.

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Just to add, I made a mistake earlier, the gauge does not go full until after is "initializes" (as in jiggles around). At that point, the one gauge goes to full speed, and the other to zero. Sorry about the mistake.

you might want to call a priest

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Hybrid dude,

If you look down the list you will find my thread concerning the same issue on my 1998 Response LX. I finally got my right speedo to work but it is now reading way too high. The toggle switches that are supposed to calibrate the speedos don't work properly. Both speedos and the tach have a plastic ring around the outside of the gauge under the clear plastic lens. This ring is drooping and my right speedo needle was hanging up. I took it apart and removed the ring but it still reads too high. I have come to the conclusion that the MDC-1600 (MDC stands for 1600 in roman numerals) is bad even though all of my other gauges work fine. I use my tach to determine speed. 3000 RPM is about 30-31 MPH. You can also mount your GPS on the windshield to the right and that works great since there's a power source by your right knee.

Now if you want to spend the $$ to get it fixed, plan on shelling approx $230 for the computer and $200 each for the gauges and I think you can still get the switches but I don't think I want to go that route. I'd rather save the money to replace seat skins down the road.

If you send me an email, I'll forward you a troubleshooting pdf file on the MDC.

cgpilot at yahoo dot com

Wood

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