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malfunctioning depth sender

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rbpc25
1st Mate

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USA
86 Posts

Initially Posted - 07/13/2016 : 15:59:32

just replaced my depth gauge with a new unit (Faria had a recall on my model/year)

but the new one blinks stupidly too (0.0' in 6' of water)

so I am looking at the sender

already suspicious with one loose and one missing screw on the top of its dim head

any thoughts on how to troubleshoot? anyone heard of Airmar?

thanks all!

Rolf in MA
C25 #4959

Edited by - rbpc25 on 07/15/2016 09:00:16

Lee Panza
Captain

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Response Posted - 07/13/2016 : 21:16:59

quote:
Originally posted by rbpc25

...any thoughts on how to troubleshoot? anyone heard of Airmar?

Rolf: Airmar is the primary manufacturer of sending units. Most of the units provided by the big brand names in electronic toys come from Airmar.

I'm pretty certain this one's a P79 sender, which shoots through the hull with no hole. The base portion is just a well, but the flange at the bottom is on an angle to the main axis, so it can be placed on a sloping portion of the hull and still point the sending head downward. The sending head itself is also cut on an angle, so by rotating the two sections in opposite directions it's possible to aim downward from a wide range of angled surfaces. All of this is irrelevant to you at this point, however, because it's already installed.

However, since the signal from the head doesn't travel well through air, it's necessary to fill the lower section with fluid before inserting the head. The white gunk around the bottom is a sealer as well as an adhesive, which is supposed to keep the fluid from leaking out. The instructions talk about filling it with propylene glycol (a particular type of radiator anti-freeze), but if any of it has leaked out leaving air space the unit will not work.

I found I was getting unreliable and intermittent operation when I first installed mine, using propylene glycol, and I was getting really annoyed until I replaced that stuff with ordinary sea water. It has worked fine ever since (and after calibrating my display unit it is giving accurate and reliable readings).

If your read-out unit was designed to work with this sending unit, and the read-out unit is not defective, the problem is likely that the well under the sending unit is not full (even bubbles will seriously interfere, and if there is any air gap at all it simply will not function). The sending unit unscrews from the base by turning counterclockwise after removing both screws. The screws simply keep it from rotating, and the single one partly in could probably do the job. On the other hand, without both screws driven home it might be loose enough for some of the fluid to have sloshed out. I can't remember if it's important to have both screws in tight.

Hope this helps.

There's plenty of literature on this unit available online from Airmar - including the owner's guide.

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

Edited by - Lee Panza on 07/13/2016 21:20:31

rbpc25
1st Mate

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Response Posted - 07/14/2016 : 10:54:19

thank you Lee, that is outstanding information - hope to have her up and running in short order

Rolf in MA
C25 #4959

delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 07/14/2016 : 11:01:20

Mine (also an Airmar) stopped sending a while ago too. I get mostly 0.0 wherever I am, but every once in a while it'll get what appears to be a "real" return, but I've learned to ignore it. It just blinks stupidly most of the time. When I really need to know my depth (mostly when we're crabbing), I've got a Humminbird fish finder rigged up with the transducer right next to the old Airmar, shooting through a wad of toilet wax which works pretty well.

Next time I take the boat out of the water, I want to try to either replace the Airmar, or put in a completely new depth/speed system.

Edit: when I talked to the manufacturer about it, they told me to listen to the transducer with a piece of hose. You should hear a distinct "click" noise as it transmits. Mine makes no such noise, but the Humminbird does, so that might be worth trying just to see if you're getting a transmission at all.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - delliottg on 07/14/2016 11:06:11

rbpc25
1st Mate

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86 Posts

Response Posted - 07/14/2016 : 11:05:46

delliottg, did you try re-filling the 'tank' with PG or seawater?

Rolf in MA
C25 #4959

delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 07/14/2016 : 11:07:53

No, I was unaware. I'm pretty sure mine's a through hull and doesn't sit in a puddle, but it might? I'm not sure how to tell, I'll read through this thread again when I'm not so crushed at work so I can better understand what to try.

I'd love to get the depthsounder working again without having to replace it.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

rbpc25
1st Mate

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86 Posts

Response Posted - 07/14/2016 : 11:13:27

I thought mine was a thru-hull too, but apparently it just sits in a splat of goo, and in order to read properly, some kind of internal reservoir must be filled entirely with fluid - Airmar recommends antifreeze (propylene glycol), but my hero, Lee Panza, says sea water works better - I am heading over shortly to disassemble and see what's what - will report back

Rolf in MA
C25 #4959

islander
Master Marine Consultant

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Response Posted - 07/14/2016 : 11:41:02

Im surprised about using sea water, Sea water is just not sterile and I would think it would get nasty over time but if it worked for Lee... I guess your out of luck if you sail on a lake

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 07/14/2016 11:58:40

delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/14/2016 : 15:24:50

quote:
Originally posted by rbpc25

I thought mine was a thru-hull too, but apparently it just sits in a splat of goo, and in order to read properly, some kind of internal reservoir must be filled entirely with fluid - Airmar recommends antifreeze (propylene glycol), but my hero, Lee Panza, says sea water works better - I am heading over shortly to disassemble and see what's what - will report back

Can you take some pictures as you go and post them? If I can fix mine without taking the boat out of the water, that'd be great.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Voyager
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Response Posted - 07/14/2016 : 17:11:46

Not for nothing but when it gets cold enough even seawater freezes. 28� or 29� if memory serves, and that could create problems due to ice expanding.
My transducer is bedded in toilet bowl wax and so far, so good.
In the case of this configuration, I'd recommend using a big wad of petroleum jelly inside the transducer tube to eliminate any air.
Both PG and seawater are prone to seeping out of the 'seal', but petroleum jelly would just stay there in place unless the temperature inside the boat exceeded 150�F+ for an extended period. Being in contact with the hull in the water, this is extremely unlikely.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

islander
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Response Posted - 07/14/2016 : 17:35:19

Bruce, Good point on the sea water freezing. Not a good idea for us northerners. I guess that's why they use antifreeze.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

sethp001
Mainsheet C-25 Tech Editor

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Response Posted - 07/14/2016 : 18:03:54

quote:
Originally posted by delliottg
Edit: when I talked to the manufacturer about it, they told me to listen to the transducer with a piece of hose. You should hear a distinct "click" noise as it transmits. Mine makes no such noise, but the Humminbird does, so that might be worth trying just to see if you're getting a transmission at all.

Thank you for this troubleshooting clue, David!

Seth
"Outlier" 1987 Catalina 25 SR/SK/Traditional Interior #5541
"Zoo" 1977 Morgan Out Island 30
"Nomad" 1980 Prindle 16
"Lost" 1988 Catalina Capri 14.2 (sold - yay!)
"Marine Tex 1" Unknown Origin POS 8' Fiberglass Dinghy
https://whichsailboat.com/2014/07/27/catalina-25-review/

rbpc25
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Response Posted - 07/14/2016 : 20:09:33

got postponed a day
will send pics when I get 'er apart
and ditto on the tube-listening tip!

Rolf in MA
C25 #4959

rbpc25
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Response Posted - 07/15/2016 : 08:23:18

OK, so this a remarkably low-tech

there is a housing that bonds to the hull (it has no bottom, so will leak if not perfectly sealed - hence the seeping, the petroleum jelly suggestion, etc)

the sensor itself has an angled bottom, so it can rotate to match the slope of the hull

there are multiple screw holes to secure the desired angle, and prevent unwanted rotation

my 'resevoir' had precious little antifreeze

so I am about to fill up, re-install, and see what happens

(there is not much room for any liquid of any kind, once the sensor is re-inserted - it's a fairly snug fit
I am guessing frozen seawater wold not be a big problem, given how little liquid is in there, and the likelihood of breaking the caulk seal before cracking the housing
in any case, would be simple enough to unscrew/remove the top as part of winterization routine)

Rolf in MA
C25 #4959

rbpc25
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Response Posted - 07/15/2016 : 08:25:30

(I am not a fan of the caulking job the PO did, so I will likely remove at some point, scrape, and re-caulk, with a fairly robust and resilient caulk, hitting both sides of the joint)

Rolf in MA
C25 #4959

rbpc25
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Response Posted - 07/15/2016 : 08:48:10

well, that was easy

all of a sudden, we have depth :)

thanks all!

Rolf in MA
C25 #4959

islander
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Response Posted - 07/15/2016 : 12:51:37

Without re caulking the little bit of liquid won't take long to seep out. I would also try the antifreeze if that's what the manufacturer calls for. It wasn't the antifreeze that caused the problem but rather the lack of it.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

rbpc25
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Response Posted - 07/15/2016 : 13:03:38

I did use PG antifreeze

and I have dried/cleaned thoroughly around the caulk and will be able to monitor any 'seepage'

seems to me liquid can escape via evaporation, too (or even excessive heeling)
not the tightest of fits, that cap

Rolf in MA
C25 #4959

delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 07/15/2016 : 13:21:35

quote:
Originally posted by rbpc25

well, that was easy

all of a sudden, we have depth :)

thanks all!

That's great! But looking at your photo I know for a fact that my transducer penetrates the hull, so I don't think this fix is going work for me, but it won't stop me from looking. Maybe I'll get lucky.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Lee Panza
Captain

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465 Posts

Response Posted - 07/16/2016 : 08:57:07

...toldja so!

Sometimes we 'know-it-alls' around here really do know what we're talking about. Most of the time, actually, from what I've read. This forum is an invaluable asset. I'm glad you got it fixed, Rolf. Now, check the instructions for your display unit and see if you can calibrate it, so you don't have to do a mental calculation every time you read the gage.

BTW, you may already be aware of this, but the more "robust" caulking materials attack some plastics. Look into this before you do the upgrade you intend.

- Lee

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

Edited by - Lee Panza on 07/16/2016 09:01:01

rbpc25
1st Mate

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Response Posted - 07/21/2016 : 07:00:03

OK, so the fresh coolant all drained out in a few days - nice green puddle 8" away in the lowpoint of the forward bilge

I am cutting away the old sealant, removing the container, and replacing

any idea what is recommended sealant, and how to install it?

thanks

Rolf in MA
C25 #4959

rbpc25
1st Mate

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Response Posted - 07/21/2016 : 09:06:49

looks like Silicone I or II (definitely not what the PO used)

Rolf in MA
C25 #4959

rbpc25
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Response Posted - 07/21/2016 : 09:21:34

P79 install guide: http://www.airmar.com/uploads/InstallGuide/17-217-01.pdf

Rolf in MA
C25 #4959

islander
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Response Posted - 07/21/2016 : 10:29:50

Definitely use the sealant that is called for in the install directions. Anything else might soften with the antifreeze.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

rbpc25
1st Mate

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Response Posted - 07/21/2016 : 10:43:20

yup, fresh tube of S2 ready to go

Rolf in MA
C25 #4959

sweetcraft
Admiral

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Response Posted - 07/31/2016 : 14:32:14

Just adding in with my experience. Used silicone over 30 years ago and sounder still works great. In the 79 it could be even longer. Have had issues with other boats too close and their sounders signals interfer. A new discovery is when a celphone charger is on the depth sounder does new numbers.

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