Trim Tabs run down, but not up

jpherron

New Member
Feb 19, 2011
11
Virginia Beach
Boat Info
240 SD 1999
Engines
5.0 MPI
I held the trim tab switch too long and blew the 15amp fuse on the engine pig tail. (Kills entire boat electrical system BTW.) This happens a lot, I can't tell when tabs are all the way up or down, and if I hold the switch for more than a second or two after reaching full travel the fuse will blow. I've gotten used to it and just carry lots of extra 15amp fuses. This weekend it happend again, but afterwards I've been unable to trim up. Press to trim bow down and motor runs, but nothing happens if i press to trim bow up. Seems like a bad connection type problem to me, but not sure where to look. The splice plug at the trim tab motor seems to be seated, the fuse behind the instrument panel looks good. What should I do next?

-john

Irish Wake
1999 240 Sundancer
5.0 MPI Alpha One
 
John,

The Fuse for the Bennett Trim Tab system should be 20 amps, and holding the Trim Tab swich too long should never blow the fuse. I suspect that it is wired incorrectly, and that the Trim Tabs need to be on a circuit that does not include a 15 amp fuse.

Here is a link to a video that covers how the system works and basic troubleshooting http://www.bennetttrimtabs.com/videoplayer.php?vID=10


Below you will find troubleshooting you can print and take to the boat.

I would make sure that the ground wire at the pump has clean connections at both ends and all the other electrical connections are in good shape. Then check out step 3.

Let me know what you find.

Tom McGow
Bennett Marine

Fluid: Automatic Transmission Fluid (ATF) any type. Hydraulic Power Unit is self bleeding, running the Trim Tabs up and down 3-4 times will purge air from the system.

Fuse: 12 volt system use 20 amp in-line fuse on positive. (24v & 32v use proportionately smaller)

Red= Port Valve
Green= Starboard Valve
Blue=Motor Forward (pump pressure)
Yellow= Motor Reverse (pump retract)
Black on HPU=Ground
Orange on Helm=Control Positive

Troubleshooting

1.If one side is not operating reverse hydraulic lines on the front of the Hydraulic Power Unit to determine if the malfunction is in HPU or actuator / hydraulic lines. If after reversing the lines symptom shifts to the other side the malfunction may exist in HPU. If the symptom remains on the same side, malfunction may exist with the actuator / hydraulic lines

2. Is the unit receiving a solid 12 volts? Low voltage will some times cause the solenoids to not open preventing the tabs from moving even though the pump motor is running.

3. Conduct the following test:
Remove the wires from the helm control and touch together as follows:

Operation=Reaction
Orange (+), blue, red= Port trim tab down
Orange (+), blue, green=Starboard trim tab down
Orange (+), blue, red, green= Both trim tabs down
Orange (+), yellow, red= Port trim tab up
Orange (+), yellow, green=Starboard trim tab up
Orange (+), yellow, red, green= Both trim tabs up

If the trim tabs function correctly for each wire grouping then the switch is at fault. Also note that any loose or missing screws on the back of the switch (whether a wire is connected there or not) can cause the pump to malfunction.
 
John,

... holding the Trim Tab swich too long should never blow the fuse. ...

Tom, that's nice to know. I have never had a fuse blow in mine, but have always been overly cautious since taking delivery of my boat. I bought in new and during delivery, the SR Dealer made it a point to advise me that;
1.) You can hold the buttons to retract the tabs all day long and no problem, but
2.) When putting them down, do not hold them too long or you will blow the fuse.

Seemed rather "fragile" to me at the time and I always wondered about this, but never took the time to dig into it.

Thanks,
 
Great info! Thanks Tom. The only thing I might not have been clear enough about is that the fuse I keep blowing isn't anywhere in the trim system as far as I can tell. It's a 15amp fuse in a small four fuse pigtail that hangs off the top of the Mercruiser, and it first blew when I tried to run the tabs in opposite directions at once. (I didn't know that would comand the HPU to run two directions at same time.) When the fuse blows the entire electrical system dies, engine stops, VHF dies, everything. It now blows anytime I hold the switch too long at full travel. The trim system fuse on the back of the instrument panel never blows...I'll go check all the connections, hopefully i won't have to remove the HPU to troubleshoot since it's extremely tight and hard to reach with the engine installed.

-john
 
Chuck,

As long as the system is fused properly (20 amps) you can hold down the down buttons with no worries about blowing a fuse. The pump motor has a thermal disconnect that protects it if it gets too hot, but your fingers would get a cramp if you held the switch that long :)

Tom
Bennett Marine
 
John,

If the Trim Tabs are blowing that 15 amp fuse, then it's in the same circuit and should not be. The Trim Tabs should be protected by their own independent 20 amp fuse. Yes, on older systems running one Trim Tab up while running the other down at the same time can blow the fuse. Currents systems utilize a lock out feature in the switch to prevent this from occurring.

Let me know what you find and I will be delighted to help.

Tom
Bennett Marine
 
Tom,
Thanks for the info, I think I got it fixed. The troubleshooting info with wire colors helped a lot when I started jumping the leads to see whether the HPU and solenoids worked. I cleaned everything, checked all connections, and now it seems to work fine. I also spliced in a device to prevent the HPU from being commanded to operate in opposite directions at the same time.

I would like to know why there's a 15amp fuse on the engine that can be blown by the trim tabs, and where the 20amp inline fuse is that you talked about. I don't see it down by the HPU or in line with the switches behind the instrument panel. The 15amp fuse seems to be protecting a lot more than trim tabs, judging by the fact that everything electrical on the boat dies when it blows. (Including the engine.)

Anyway, thanks again for the responsive Labor Day help!

-john
 
John,

That sounds good, but you are right about worrying about that 15 amp fuse! Normally the 20 amp fuse for the Trim Tabs is on the orange wire that leads to the back of the Trim Tab switch:
sys.jpg


Number 34 in the drawing.

This circuit should be separate from the 15 amp fuse you keep blowing.

Tom
Bennett Marine
 
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Ok, I'll look again in the area behind the panel. I probably just missed it, not following the wires far enough.
 
15 amp fuse

I'm bringing this thread back up. I bought jpherron's boat from him last month and it still has that 15 amp fuse on the pigtail that blows and kills EVRYTHING on the boat anytime the trim tab switches are held down too long. It did it to me when we took it out for the sea trial and he was so experienced with the problem he had it fixed in less than a minute, including time to show me where the fuse pigtail was. John kept a bin full of 15 amp fuses just for this problem and the bin is about half empty so I assume he ended up just learning to live with the problem and replacing that fuse became a normal part of his boating experience. I'd prefer it not become a normal part of mine.

I am attaching two photos; one of the pigtail, and another showing where its circuit joins the wiring loom at the rear of the engine. The lines on the pigtail go into a main wiring loom and there is no way to know where they go from there apart from cutting the loom's wiring shield off of all of the wires letting them all go loose and following the lines from there... no way I'm going to do that and is probably why John quit before he figured it out.

As he stated, this boat had a new 5.0MPI swapped into it in late 2009 or early 2010. I don't know what the original engine was but it was probably a carbed 5.7. I am hoping that by showing photos of the actual pigtail, fuse, and routing into the main wiring loom that someone here will recognize what this circuit is and tell me how in the world the trim tabs got into it and why it kills the entire electric system on the whole boat when it goes.

It would be a real shame if that single 15 amp fuse in a pigtail block of 20 amps is there only because the mechanic ran out of 20 amp fuses so he just stuck a 15 in the pigtail while a 20 was supposed to be there the whole time... I would love to be assured by someone here that I can safely replace that 15 amp fuse with a 20 which probably will fix this problem (opinion based on prior posts in this thread stating that the Bennett trim tabs need 20 amps).
 

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Bennett Trim Tabs need to be protected with a dedicated 20 amp fuse or breaker. It will blow a 15 amp. So it needs to be changed :)

Tom McGow
Bennett Marine
 
Thank you Tom, I put one in and the fuse does not blow now. However.... with the pump working and not blowing fuses, this has revealed that I do have a version of the problem noted in the original title subject of this thread.

Now that the fuse does not blow I have discovered that the starboard trim tab will not retract/go up. I unscrewed the actuators and switched sides and it stayed on the starboard side so it is not the actuator. I assume it is not the line since it does a great job of forcing ATF fluid into the actuator and pushing the tab down. However, once down it will not release the fluid back into the line to allow the tab to spring back up. I can hear the HPU working and it does raise the port side, so the pump itself has power and is good.

This morning I just re-read your troubleshooting post #2 that suggests reversing the lines on the front of the HPU to determine if it is the HPU or the actuator/line that is the problem. I think I sort of did the same thing by unscrewing the actuators and swapping them to the other side, right (?) Following the logic, I assume that something internal in the starboard tab control of the HPU is stuck and not opening the line to allow the fluid back into the HPU. Does this sound right to you and does it sound like a problem you’ve seen before and know what is wrong….. would it be a fixable problem or would it require replacing the entire HPU?

I appreciate any insight you can provide. Thanks!
 
Gerald,

Since the starboard Trim Tab will go down, but not come up, the actuator is likely fine as confirmed by your swapping them side to side.

Also since it went down it means the the solenoid valve on that side is working. And since you hear the pump motor running when you try to retract it this indicates that the valve for the starboard side is not getting power when you push the switch to bring it up. So this points to a switch failure or a loose or missing connection at the switch. It is also very important that the system is getting good voltage since the valves require more current to open when bring the Tabs up (so cleaning both ends of the black ground wire at the pump is always a good idea).

Do you know if it a Bennett Switch on your dashboard? SeaRay has used other manufactures switches on some models.

If it is a Bennett switch the first thing to check is if all 12 screws on the back are clean and tight (even if they don't carry a wire).

In the troubleshooting below check out step 3. That will allow us to isolate the problem if you do it right at the pump and right behind the switch. If you energize the yellow wire and the green wire at the same time the starboard Trim Tab should retract.

Also look at step 6. Given the age of the boat you may have that relay.

Let me know what you find!


Tom
Bennett Marine

Tom McGow
Bennett Marine

Fluid: Automatic Transmission Fluid (ATF) any type. Hydraulic Power Unit is self bleeding, running the Trim Tabs up and down 3-4 times will purge air from the system.

Fuse: 12 volt system use 20 amp in-line fuse on positive. (24v & 32v use proportionately smaller)

Red= Port Valve
Green= Starboard Valve
Blue=Motor Forward (pump pressure)
Yellow= Motor Reverse (pump retract)
Black on HPU=Ground
Orange on Helm=Control Positive

Troubleshooting

1.If one side is not operating reverse hydraulic lines on the front of the Hydraulic Power Unit to determine if the malfunction is in HPU or actuator / hydraulic lines. If after reversing the lines symptom shifts to the other side the malfunction may exist in HPU. If the symptom remains on the same side, malfunction may exist with the actuator / hydraulic lines

2. Is the unit receiving a solid 12 volts? Low voltage will some times cause the solenoids to not open preventing the tabs from moving even though the pump motor is running.

3. Conduct the following test:
Remove the wires from the helm control and touch together as follows:
Operation=Reaction
Orange (+), blue, red= Port trim tab down
Orange (+), blue, green=Starboard trim tab down
Orange (+), blue, red, green= Both trim tabs down
Orange (+), yellow, red= Port trim tab up
Orange (+), yellow, green=Starboard trim tab up
Orange (+), yellow, red, green= Both trim tabs up

If the trim tabs function correctly for each wire grouping then the switch is at fault. Also note that any loose or missing screws on the back of the switch (whether a wire is connected there or not) can cause the pump to malfunction.

This test may also be done right at the pump by substituting a "hot lead" for orange. There is usually a connector to the wire harness within a foot or so of the pump. You want to check this connection for corrosion. You may wish to cut the connector off on the pump side and try the test on bare wires.

4. If you suspect corrosion on the wire connector near the pump, cut it out, test as above and reconnect using butt splices.

5. If you conclude the problem is in the pump, contact me. Bennett Trim Tab Systems carry a five year warranty.

6. Check to see if there is a relay in line on the wiring harness near the hydraulic power unit. If there is it is an Interrupter Relay (IR1000). It prevents the system fuse from blowing if you try to actuate one trim tab up and the other down at the same time. After you test as outlined above, try removing the relay from the wiring harness and retest the unit.(Note: the interrupter relay is no longer used in current Bennett Trim Tab systems and has been replaced with a Switches that "lock out" preventing a blown fuse).
 
You are a wealth of information. Thanks.

I don't know if it has a Bennett switch or not; I'll note if it is when I remove the access panel to the helm tomorrow and start troubleshooting per your instructions.

I was really confused because I thought the switch was good because I could hear the pump working when I used the switch. From your post (and I just viewed your troubleshooting video in this thread) it is obvious that the switch activates two functions - it powers the pump and also engages the solenoid valve. The yellow wire is obviously working/hot when I press the switch. It does sound like a bad connection of the green wire on the switch board when the switch is pressed to bring the tab up. After viewing your video and reading you reply, that sounds like the prime suspect and will be my first check - if that is not the problem, then I'll continue with the rest of the troubleshooting process.

I did notice jpherron's post long ago in this thread when he followed your instructions and cleaned the connections on the board and it seemed to fix a problem for him at that time. These are 14 year old wires/connections on a saltwater boat and may need some more attention.
 
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Sounds like a good plan!

Yes, it is likely a a faulty connection for the green wire or an internal failure of the switch. Step 3 right at the switch is really a great way to test it, as well as cleaning and tightening all the connections on the back of it.

While you are at it check out all the connections in the system, particularly both ends of the black ground wire at the pump and the system will likely run for another 14 years :)

Below you will find a system diagram and a picture of the back of the switch you may find helpful.

Tom
Bennett Marine




12 volt positive is connected to any screw on the "+" strap.
 
I cannot tell you how much I appreciate your help. Before receiving your input, I was resigned to thinking I might have to crawl upside down into the awkward back corner of a crowded small engine bay to mess with the HPU and possibly completely replace it. Your direction nailed the problem precisely - it was a green-wire faulty connection on the switch (not Bennett, BTW). A ten minute fix with a small file and contact cleaner to clean up the connection. Thank you, thank you, thank you.
 
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