Trim tab position indicator problem

[kashurst]

I have a set of Bennet hydraulic trim tabs, hydraulically everything seems great. They work correctly. I have separate port and starboard indicator meters at both helms, with Carling switches used as the control switches. The starboard indicator dials seems to have a mind of there own. Sometimes it reads correctly, most times it indicates fully down. Upper and lower helm indicators seem to behave in the same way.

Almost certainly a dodgy connection somewhere, probably at the sensor. First place to check is the sensor in the hydraulic ram. Rummage around in the lazarette, hydraulic pipes all there but no wires coming through the transom. Can't see any wires on the outside of the transom. Anyone know what my indicators could be measuring?

 

[Portofino]

There are 3 " hydraulic " pipes identical on appearance except one is a Boden cable . It's wire is attached with an adjuster on the flap .
Obviously 2 are actually hydraulic pipe to the ram
They all enter the boat above the WL under the platorm
Presume the boden cable is attached to the inside of the transom to a potential ohmmeter which gives a signal to the gauge S ?
Point is it looks like a H pipe but it's not

 

[volvopaul]

I have a set of Bennet hydraulic trim tabs, hydraulically everything seems great. They work correctly. I have separate port and starboard indicator meters at both helms, with Carling switches used as the control switches. The starboard indicator dials seems to have a mind of there own. Sometimes it reads correctly, most times it indicates fully down. Upper and lower helm indicators seem to behave in the same way.

Almost certainly a dodgy connection somewhere, probably at the sensor. First place to check is the sensor in the hydraulic ram. Rummage around in the lazarette, hydraulic pipes all there but no wires coming through the transom. Can't see any wires on the outside of the transom. Anyone know what my indicators could be measuring?

The bennet had a potentiometer inside the ram cylinder that gives a signal as the ram rod passes over it . If it's faulty usually means a new ram .

 

[AllanG]

The bennet had a potentiometer inside the ram cylinder that gives a signal as the ram rod passes over it . If it's faulty usually means a new ram .

You can buy just the Bennett upper hinge assembly from Magic Marine Ltd, which includes the potentiometer coil, and it's very easy to change this part.

 

[vas]

reviving an older thread on a similar topic just to have possible solutions together...

so bought new Bennett upper hinge assemblies for myself and a friend.
I bought (STUPIDLY!!!) the NMEA2000 kit which only works with Lowrance displays (but that's not the point), and for him I just got normal upper hinges only.
Have one on my desk trying to figure out how the hell this thing works.
OK, I can see there's a coil on the hinge assembly and a metal rod that fits in it (and all together screw in the ram)

Now, no matter what I do I only measure 240 Ohms on the two wires coming out of the sensor, no matter in or out I do, that's it. Occasionally will flash 239 Ohms for a sec and then back on 240.
Note I'm at home so obviously I have the thing running DRY, no oil around it, could that be the problem?
Note2 i've tried both assemblies both do the same, so cannot really be that I've got broken kit.

any ideas?

cheers

V.

 

[aquatom]

They are inductive sensors so the resistance will not change.

 

[vas]

They are inductive sensors so the resistance will not change.

I thought as much, but then it doesn't make any sense... will try with another (better) multimeter and give it 12V and measure drop or whatnot.
BTW, 220-260 Ohms is the factory spec value for the coil.

V.

 

[BartW]

I thought as much, but then it doesn't make any sense... will try with another (better) multimeter and give it 12V and measure drop or whatnot.
BTW, 220-260 Ohms is the factory spec value for the coil.

V.

are you sure that it is not AC on the sense wires in a standard bennett system ?
then inductive sensors make sense,

I have such a system on the Karnic,
tomorow we go out with her,
I'll try to have a look, but acces to the system is very is tough...

 

[BartW]

thinking about it,
the sensor in BA is also a old Bennett system,
its a floater with a metal shaft, gliding in a opening / coil ?
most probably the predecessor of the more modern compact system

 

[vas]

no idea Bart,

would rather it's not AC, as how the hell am I going to produce AC Voltage to feed the thing???

yes that's the one Bart

https://www.hodgesmarine.com/BENNETT-MARINE-NMEA-2000-TRIM-TAB-INDICATOR-KIT-p/bennmea1.htm

cheers

V.