Electrical interference with depth finder

[lancelot9898]

I have an old 25 year old Impulse digital depth finder at the helm with the transducer installed in a thru hull fitting. It's worked fine for the past 24 years, but recently it gives bad readings whenever the engine is running. Under sail it still does fine so there must be some degradation in the transducer cable as it passes through the engine space. Is there a simple and easy fix such as wrapping the cable with some shielding as it goes through the space? Replaceing that cable would not be easy since it's difficult to access on both ends plus not sure if even possibe since the transducer end in potted in epoxy.

[kd3pc]

your old gear reached the end of it's useful life some years back, you will likely find that disturbing the cable run will cause even more issues.

Best bet, replace the entire system with one of more current technology and reliability.

If you want to trouble shoot, would need more info...gas or diesel. I suspect gas as there is really not much "electrical" about the diesel. You may find that battery cables or other signal cables have moved in relation to the pulse finder cable...

Best of luck

[Cptken]

Have you changed anything in the charging circuit? Just because it happens when the engine is running doesn't mean it has to be isolated to the engine comptartment. Might also ensure the connections are tight and corrosion free.

[lancelot9898]

Nothing has changed in the past 4 or so years. It's a Balmar high output alternator with an external regulator on a Perkins 4-108 and that alternator is what I suspect is where the interference is coming from......so it's maybe a degradation of the cable or possibly a problem with the alternator

[Hartley18]

See my reply on the other site.