Topic: SOS - Erratic Depth Readings ???

[MTBob]

Re: 998c, installed in 2013
After working fine last year and the beginning of this year, all of a sudden the depth readings are jumping all over the place.  At first it was in shallow water less than 20 feet.  The readings would go from 1 to X and then eventually begin apparently reading correctly at deeper water. 
I did a full reset and that seemed to help - for a while.
But, then today, running along at 25mph at depths of 150 feet, the readings went to 1, 2 , 3 feet, jumping all over the place.  The screen often goes blank or does not adjust automatically to correct screen display (auto depth).  I am using a Y splitter and currently have the boat in the water - will be pulling it out tomorrow.
Can anyone give some advice about what cause this problem?
Thanks in advance, Bob

[biggs aquaholic]

I have a 998c hdsi unit that does the eratic depth readings when on clear mode. I have already ruled out everything except that my unit is faulty. We have two of these and one works perfect, but the one  does this eratic depth reading but my water collum is always showing the correct depth even when the number is jumping around eratically.What software are you using? my software is 7.090.

[ljbev]

If you have a flip up mounted transducer, it may have flipped up  It measures the distance in which ever direction its pointed....mine did this shortly after I installed it.  I kinda thought the tension was not tight enough.  I now have to get wet or haul the boat.  I plan on squeezing the bracket with a channel lock before snapping it back into place...
Good luck to you

[rnvinc]

ljbev makes a good suggestion to check...

If that shows no issue...:

(I'm assuming your AS SIDB Y cable setup includes a shoot thru hull Dual Beam xducer for the 2d readings)...

To test for other issues...disconnect the AS SIDB Y cable and plug the Dual Beam xducer directly into the back of the unit...(change the Transducer Select menu to the Dual Beam so that the unit does not ping the SI channels while testing the Dual Beam xducer..)...

If the issue is fixed...then the AS SIDB Y cable is defective...

If the issue is still present...then the Dual Beam xducer or the unit has a problem...(or possibly the Dual Beam xducer has come loose from its epoxy and allowed air to get between the Dual Beam xducer and the hull )...

Test this 1st to eliminate the chance that the AS SIDB Y cable is bad and then post back with results...where we can continue to troubleshoot your issue...

Rickie

[MTBob]

Thanks ljbev, position of the transducers was one of the first things I checked.  Both were in the down position.  While the boat was in the water I backed into a sand beach and did a hang check for position & whether any gunk had stuck to the units.  It all looked fine to the eye and touch.
However, now that the boat is out of the water, I need to recheck alignment of the transducers.
Bob

[MTBob]

Rickie: (Sorry for the delay in responding, I've been in a remove location on the Snake River on the Idaho/Oregon border.)
I use two transom mounted transducers.  Your process of elimination makes sense.  However, it seems unlikely that the y-cable would all of a sudden become defective after more than a year's use.  I see no abrasion or worn cables going to the transducers.
But, I've got a small problem now.  I've taken the boat out of the water and will likely not get it back to water for several weeks.  Where I live in Montana, the nearest water is about 1 1/2 hours away, so trying to run tests gets to be a bit problematic.
Making this issue even more frustrating is that the erratic readings don't seem to behave with any regularity - seemingly random.  I made a series of screen shots (.png files) of the events if that helps.
I must confess, it is disappointing that this $1500 fish finder doesn't have a self test to determine whether either the transducers or the display unit is defective.
Before I start taking cables apart and reconnecting them (not a particularly easy job), I'll see if I can determine some kind of correlation to what causes the faulty readings when I'm on the water next. 
At this point I've lost confidence in the accuracy of the depth readings (and somewhat the reliability of the whole system), a really big problem when trying to navigate unfamiliar waters.
Bob

[rnvinc]

As the AS SIDB Y cable is basically nothing more than a cable splitter, I know it seems unlikely that any part of it can fail...

More often with the AS SIDB Y cable ...it's the added cable connections than create more possibilities of a bad connection...

If you determine that your issue is narrowed down to the AS SIDB Y cable, you can try bending the pins in all the connectors slightly to try and get better contact...

Rickie

[MTBob]

Thanks Rickie.  I agree pins in the cable could be an issue.  That suggestion makes a lot of sense.  I've wiggled the cable assembly connector at the head and visually check for bent pins.  I now need to look at the Y splitter and see if everything is OK.  It will be a week or two before I can get to this again.
Regards,
Bob

[Humminbird_Greg]

Bob,
If this happens while idling along or drifting, try taking the AS-Si-DB-Y cable out as Rickie suggested but plug in each transducer separately to see if either/both work correctly.  You should do what troubleshooting you can but an intermittent connection somewhere can drive you nuts trying to figure it out.  It is rare but the AS-Si-DB-Y cables do fail.

If you have access to another Humminbird unit (a non-DI model) try connecting it to your transducer and power connections to see if the same thing happens or not.