Thanks for the reply Larry.

The Bennett website only gives basic info but the coils should measure 220
to 260 ohm when measured between the two inner wires of the screened cable
to the tabs. My port one is open circuit.

At the rear the cable disappears through the transom so I cannot determine
if there is a plug and socket and the Bennett site gives no clear info. I
cannot get at the outside when the boat is in the water as the tab is under
the bathing platform so further investigation will have to await my next
liftout.

The hydraulic fluid has now been checked and is OK.

I have located the UK agent for Bennett and conveniently they are less than
1 mile from my home. I shall visit them tomorrow.

Alec





"Larry" wrote in message
...
On Wed, 13 Sep 2006 19:15:36 +0100, Alec wrote:

I have Bennett trim tabs on my boat, fitted with trimindicators.

The port indicator has ceased to indicate showing full down at all times,
this happened suddenly with no apparent warning. One day in the Seine it
worked and the next in the Bay de Seine it did not.

I have read the advice on the Bennett site and determined that the sensor
appears to be at fault, that is the two red wires appear to be open
circuit.
Plugging the starboard sensor into the port socket confirms that the
indicator circuitry works OK.

I cannot easily get to the tabs whilst the boat is in the water. How does
the indicator sensor work? Can low hydraulic fluid level affect the
operation? How does the sensor wire get into the hydraulic ram?(plug and
socket?)

The tabs appear to work OK.

Alec

For some reason, I cannot always get into this newsgroup, so you may have
to email me.

The indicators work (I think) by measuring the inductance or reactance of
a
coil. A metallic rod is inserted into this coil, the distance determined
by the amount of extension of the hydraulic cylinder. Low hydraulic fluid
will certainly affect the operation, BUT the cylinder will not extend when
there is a lack of fluid. I cannot remember how the wires to the sensor
go
into the ram, but I think there is a connection directly through the
transom and the wire runs through a hole there. At the end of the wires
there must be a plug which plug into a harness.

The first place to look is the wiring going through the transom. Make
certain that the plug and socket are connected. Since you say the things
still work, it is unlikely that you have low hydraulic fluid.

Good luck. I have a pair of tabs on my 18.5' jet boat and they have
dramatically reduced the speed necessary to get on plane.
--

Larry
email is rapp at lmr dot com
9/17/2006 1:00:53 PM