bennett trim tab troubleshooting

[brian]

I have one remaining issue to fix on my explorer, the trim tabs do not operate at all.  When I try to use it, nothing happens at all, I do not hear the HPU attempting to move either tab.  I checked the fuse in the orange wire behind the switch and it is in good shape.  When I took a look at the HPU, I can see it is very low on fluid which is a problem.  I don't know if it is unusual for them to loose fluid over time, but it is well below the low level line.  

I would like to start by filling it to proper capacity and testing it, but access is tricky and I couldn't tell how to open it for filling.  I'm also concerned that if I add fluid it may be leaking somewhere and don't want to create a big mess.  I suspect the previous owner didn't do much to regularly maintain this so not sure if just adding fluid is a good idea. Since it is a 20 year old boat this may have lost fluid gradually over time, but I don't know if this is a leak or normal loss over time. The boat is in a slip and I cannot easily remove it from the water to get access to the actuators.

Any words of wisdom?

[seabob4]

First, verify that you actually have 12V on the center strip (where the orange wire is terminated) of the switch.  Once you've determined that (assuming you do have power), the next part is hard.  Remove the pump from it's mounting bracket, on the back side of the motor is the ground.  Determine if it is a "good" ground by checking for continuity between the ground stud on the motor and your ground bus bar.  If both those check good, we'll go from there.

To add fluid, remove the screw in the top of the cover, remove clear plastic cover.  On the left front side of the top of the reservoir you'll see a small round dipstick.  That is your fill port.  Use a ketchup squeeze bottle to fill ($1 at wally world), spread out some paper towels below the pump as you ARE going to spill.  The pump takes regular ATF...

[Capt. Bob]

While this isn't going to help your electrical troubleshooting, scroll down to the second post and you can see the fill port SB mentions (yes that's his hairy paw).
viewtopic.php?p=85408#p85408

Good luck.

[wingtime]

Bob the ketchup squeeze bottle to fill the HPU is a great friggin idea...  And to think I actually made a small funnel on my 3D printer to fill mine....  

[seabob4]

Wally world sells them in 3-packs for a buck...ketchup, mustard, and clear...maple syrup?

[flounderpounder225]

my tabs were giving me a headache a few weeks back, intermittent operation on one of them.  Had voltage everywhere went back to the HPU, and there was this small black box that was electrically connected in between the power and the HPU, looked it up, apparently this is the Anti-Idiot box that prevents the operator from selecting up/down at the same time, an interloc device.  disconnected it, and plugged straight into the HPU with the harness. Problem solved.  Just my .02.

[wingtime]

Wally world sells them in 3-packs for a buck...ketchup, mustard, and clear...maple syrup?

I use them for oil and such for cooking...

[seabob4]

my tabs were giving me a headache a few weeks back, intermittent operation on one of them.  Had voltage everywhere went back to the HPU, and there was this small black box that was electrically connected in between the power and the HPU, looked it up, apparently this is the Anti-Idiot box that prevents the operator from selecting up/down at the same time, an interloc device.  disconnected it, and plugged straight into the HPU with the harness. Problem solved.  Just my .02.

Marc, that is the infamous "interrupter relay", I had more problems with that stupid relay when I would do final QC on an Osprey.  But typically, if they are bad, they're bad right out of the box.

Brian, another thing you definitely want to do is to pull apart your connectors and inspect the pins and sockets.  The 4-pin flat connectors Bennett uses are notorious for corrosion...

Edit:  For those with newer sets of Bennett tabs, the interrupter relay is no longer part of the install.  Bennett (Tom actually did the design) incorporated the relay functions into the switch several years ago...

Another helpful hint.  Always check that every screw on the switch, regardless of whether it has a wire attached to it or not, is tight.  Loose screws?  Tabs no workie...

[brian]

thanks guys, I have a good starting point now.

So is it normal for these units to need fluid added periodically and if neglected for a long time would explain the very low level?  I was wondering if the fluid fell to a certain point if there was some regulator that would prevent the motor from turning on.

[seabob4]

thanks guys, I have a good starting point now.

So is it normal for these units to need fluid added periodically and if neglected for a long time would explain the very low level?  I was wondering if the fluid fell to a certain point if there was some regulator that would prevent the motor from turning on.

Brian, typically, Bennett pump reservoirs almost never need topping off.  If you can see back to where the actuators hoses come through the transom, look for any telltale red staining.  The pump will operate with no fluid in the reservoir, so that's not the deal there...

To access the hoses running out to the actuators, do it from the outside of the hull.  Remove the 3 screws that secure the triangular mounting pad, pry up under the pad to break the grip of the adhesive, then pull straight out.  Once I'm at this point, I go ahead and install new compression nuts and sleeves.  You can get them from HD cheap.  Just cut off the hose an inch or so past the compression nut, bring it with you so you get the right size nut and sleeve...

Oh, forgot, you're wet slipped.  Well, if you get her on the hard, that's how you do it...

[wingtime]

Make sure the tab is fully retracted before you crack open any of the fittings! If you don't you'll have "cherry juice"  spraying all over the place! Don't  ask me how I know this!

[seabob4]

Make sure the tab is fully retracted before you crack open any of the fittings! If you don't you'll have "cherry juice"  spraying all over the place! Don't  ask me how I know this!

Bruce, how do you...uh, never mind...

[brian]

Well I finally got the trim tabs fully operational.  Spring was slow to arrive in NY so I have not had much time to work on the boat until the last few weeks now that it is out of the water from the winters storage.  I replaced the seals in the  actuators since I had next to no fluid in the HPU.  After pulling the HPU to test and try to figure out why it wouldn't power up I found it had a lot of corrosion on the motor itself.  I'm guessing at one time it got exposed to saltwater by the looks of the motor.  To be on the safe side I decided to replace the motor and the wiring while at it.  The power feed wasn't tinned copper so I figured it was bound to be part of the problem or become a problem in the near future. After replacing all wiring and motor still no power!  I ended up removing the main power from the buss bar and connecting directly to the battery terminal and everything magically started working!

Now I know I'm loosing some voltage at the buss bar and there is a lot of other items fed from that buss bar.  There is a fuse box between the battery and the buss bar and I expect i'm dropping voltage as a result of that.  So my next concern is what damage to other items could be occurring if they are not getting the required clean voltage.  Seems like most accessories now have there own in-line fuses for protection so I'm wondering if this main fuse to the buss bar is even needed or is it just causing more problems than it solves.

Thanks again for all the guidance so many have offered, it has been very helpful.