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costaricanwannabe 12-31-2007 07:12 PM

Troubleshooting Depth Sounder
I have a Garmin 198C Sounder chartplotter that came with the boat (a Cal 39) when I bought it in 2006. The depth sounder function started to fail intermittently last spring, and by mid-summer it completely stopped working. The chartplotting function still works fine. I canít find any troubleshooting information in the owners manual. I have tried contact cleaner on the two cables that plug into the back of the unit, but that didnít help. The boat was out of the water recently for other work, and I had hoped the spraying down of the hull would clean the transducer, but that didnít help either. Does anyone have suggestions on how to troubleshoot the problem?

TThomsen 12-31-2007 07:54 PM

First make sure all your fittings and connectors are clean and dry.

Then see if you can beg, borrow or steal a transducer that will work with your system if it works now buy a new transducer, if not then it would be a good chance that it is the wiring. Try running a new wire from your transducer to the dept sounder and see if you get a reading. If neither work call Garmin and see if they have any suggestions.


jaschrumpf 12-31-2007 08:14 PM

This probably won't help you, but it's a funny story regardless.

This summer my nephew and I took my 1975 Newport 28 over to a local marina for haulout and bottom washing. The guys were waiting for us to pull up into the slip, lifted us right up and got to work, and we were back in the water in a half-hour or so.

However, when I turned on the depth sounder before leaving, it was dead -- nada, nothing. I went back to the guys and told them what was happening, and if they could think of any way the power washing could have damaged it.

They had no ideas, but they volunteered to pull us up again so I could have a look at the hull to see if anything had come loose, or whatever. This they did -- for no extra charge -- and nothing did we find. I resigned myself to a pricey fix, and when they dropped me back in my nephew went below to check it again as I was tipping them an extra $20 for their trouble.

He came up with a big grin on his face and told us all, "It's working now! I just wiggled the wires on it and it came right up." All of us looked around at one another, rolled our eyes and had a good laugh.

I thought it was GREAT of them to offer to lift us again to have a look, without asking for more money. I will definitely go back to them for more work when necessary.

So, have you tried "wiggling your wires" yet?

HoffaLives 12-31-2007 08:16 PM

most likely a connection problem or something in the circuits like a cold solder joint or a faulty component. the depth sounder is a high power circuit and a failure of something internal not unlikely.

fortunately basic depth sounders are pretty inexpensive.

thekeip 12-31-2007 09:25 PM

Is your boat in or out?
Is your transducer external (thru-hull) or shoot thru?
Howard Heiper

costaricanwannabe 12-31-2007 09:25 PM

trying new transducer
I tried wiggling the wire, all the way from the transducer back to the engine compartment, where it gets difficult to trace. My wife thought at least one time that the wiggling helped, when it was in the intermittent phase, but I couldn't replicate the "fix" again. This may be a dumb question, but is there any way of trying a new transducer without pulling the boat out of the water?

haffiman37 12-31-2007 09:34 PM

The transducer is in general as a loud-speaker, coil and membrane.
OHM test and check for open/short circuit. Depending on Your test multimeter, You may even test the output from the instrument.

thekeip 12-31-2007 10:46 PM

If your boat is in the water with an external transducer, you're SOL. Your only realistic recourse is to temporarily connect a transducer with a similar instrument connector and drop it over the side.
If it's a shoot thru, check for oil or alcohol in the transducer well (whichever) and be sure the face of the transducer is "wet" bubbles. Top off if necessary. You may still need to swap transducers, as above.
I'm beginning to think you've a bum transducer...maybe it was a victim of a wayward travellift strap.

All (almost all) transducers are made by one manufacturer...Airmar. They are ceramic or sometimes crystaline, but hardly ever magnetostrictive anymore and so cannot be checked with an ohmeter.
What you can do however, if you're so inclined and have a lot of time on your hands and can get to your transducer, is to connect the transducer connector to the input of a small audio amplifier and headphone of the sort sold by Radio Shack. If your transducer is good, you'll be able to hear it in the phones or speaker if you tap it. This is vaguely related to the sort of microphone used in hydrophones. I should say that this doesn't really test the functionality of the instrument..
Howard Keiper
Sea Quest

Gryzio 12-31-2007 11:11 PM

I may be confused.

Originally Posted by costaricanwannabe (Post 243848)
I have a Garmin 198C Sounder chartplotter that came with the boat (a Cal 39) when I bought it in 2006. The depth sounder..........

We are talking Depth and not GPS? :confused: Not that it matter.

I would try some of what already mentioned, first being a borrowed Transducer if possible.

Also, check the "Pins" at the plug, are they nice and clean or green/dull? Then they need cleaned.

Another may be lose connection. Even, if, you wiggled things around. Depending how often we unplug and vibration (Coupled with other factors) the "Pin Holes (Not Pins)" may become lose and need tightened up some. I not say what you do, I have used a pair of Needle-nose Pliers and I have used something sharp like the end of a Test Light. But, I not there to see and not want to say you need to start squeezing on something with pliers when I not see what we doing. :(

Also, look at the pins! Are they split so you can slide a Feeler Gauge or something thin into them to sread out a little?

sailingdog 12-31-2007 11:34 PM

A visual inspection of the pins and socket will generally tell you if corrosion is the issue. I don't believe that's your problem—since it works intermittently, without your wiggling the wires.

It could be internal corrosion or a bad IC chip. My bet is that there was a flaky chip that had a thermal fault and as you used it, the heat from use caused it to become progressively worse, until it has basically failed completely.

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