Airmax transponder for Garmin Map 235 sounder

[Ferring]

looking for any advice regarding the above
which started showing weird depth readings over the weekend (90m jumping to 20m and so on). The Transponder is in hull fitting and the Garmin is working for all other functions. Today I scrubbed the hull (but minimal growth), checked all the cables and connectors were good. I understand that there should be an oil bath internally in the hull fitting? How do you remove the top section to check if the oil is still present?
Grateful for any hints as to next steps please?

 

[pvb]

If it's a circular Airmar fitting, the transducer should rotate anticlockwise and then lift off.

 

[rob2]

As in the first reply, the manufacturer is Airmar. Their website includes a cross reference search which should get you nine references for Garmin compatible transducers (actually I think there are four models used in different applications. Each has a link to the installation instructions, so you should be able to find all you need there.

http://www.airmar.com/xref.html

Rob.

 

[ex-Gladys]

Have to disagree, my Airmar, you have to unscrew the top ring until it's completely loose, and then pull it out

 

[pvb]

Have to disagree, my Airmar, you have to unscrew the top ring until it's completely loose, and then pull it out

Is that an in-hull fitting? Or a through-hull fitting?

 

[ex-Gladys]

Both... Log thru hull, sounder in hull

 

[pvb]

Both... Log thru hull, sounder in hull

And is it a dual frequency transducer like the OP's?

 

[Ferring]

Thanks all, yes it is Airmar. I will try and unscrew it tomorrow. I believe there should be an oil bath and if not can be re-filled with olive/cooking oil?

 

[PaulRainbow]

Thanks all, yes it is Airmar. I will try and unscrew it tomorrow. I believe there should be an oil bath and if not can be re-filled with olive/cooking oil?

Yes.

 

[pvb]

Thanks all, yes it is Airmar. I will try and unscrew it tomorrow. I believe there should be an oil bath and if not can be re-filled with olive/cooking oil?

Airmar specify propylene glycol (antifreeze).

 

[PaulRainbow]

Airmar specify propylene glycol (antifreeze).

It can be used as anti-freeze but isn't the typical automotive stuff. It's sometimes marketed as "marine antifreeze" because it's not as toxic to aquatic organisms as ethylene glycol. That said, ethylene glycol will work fine, pretty sure Airmar recommended that for a time, until someone presumably complained that it was toxic. The only benefit i can see with either of them is if you spill it, it isn't as messy to clean up as oil.

However, any veg oil, baby oil etc that doesn't attack the plastic housing will be fine.

 

[Ferring]

Well thanks again for the inputs. I removed the unit today and the reservoir was full of oil. Carefully examined the cable and no obvious signs of damage, also the connections look good.
I have removed the unit completely. Is there any way / anybody to test the unit before lashing out for a replacement?

 

[ex-Gladys]

Dangle the transducer in the water - only an inch or so in....

 

[Ferring]

Thanks but tried the dangle test and no change in readings. It has been suggested that the unit should 'hum" if active but no obvious sound coming from it?

 

[ex-Gladys]

YOu can also hold the transducer close to a radio with LW, and you may here the clicks on long wave

 

[pvb]

Thanks but tried the dangle test and no change in readings. It has been suggested that the unit should 'hum" if active but no obvious sound coming from it?

Depth transducers usually make a clicking noise. You can sometimes feel the pulsing by fingertip, or hear it if you point the transducer at a hard surface.

 

[Ferring]

Thanks again all. i have sourced some used units in USA and am n the negotiation phase of replacing the transponder.

 

[PaulRainbow]

Thanks again all. i have sourced some used units in USA and am n the negotiation phase of replacing the transponder.

By the time you've shipped a used one from the states, is it really worthwhile ?