Variable Trim System Analysis

By Dr.Volts

9-21-00

Rev.0.6

This article is intended to demystify the Bombardier electronic Variable Trim System (VTS) used on many Sea-Doo Personal Watercraft. It is based on the failure analysis of several units removed from a 1996 Sea-Doo SPX. The article should probably be titled More Than You Ever Wanted to Know About Bombardier Electronic VTS. There is a mixture of easy to understand information as well as fairly technical electronic data. The article is arranged in a question-answer format in an effort to allow non technical people to find what they need and can understand. Dont feel bad if you dont understand all of this stuff. Dont let the length of the article scare you. The article is long because it contains detailed descriptions that you can follow step by step. If you have a friend that understands fundamental electronics, get that person to look at this article, particularly the tests. The only instrument that you will need to perform the tests is a multimeter. This can be purchased for less than $50 at an auto parts store, electrical supply, or Radio Shack. The VTS is not a complex circuit as circuits go.

Summary:

This article provides comprehensive test procedures to determine which part of the VTS system (including the electronic gauge) is at fault. This will keep Sea-Doo mechanics and owners from purchasing and installing incorrect parts while trying to fix VTS problems.

The article provides the schematic circuit diagram of the VTS system in its entirety. This is the circuit that is encapsulated in the black box. The article also provides the description of how the VTS system operates, and how the VTS indicator gauge works.

This article attempts to pinpoint the root cause of the repeated VTS failures that Sea-Doo owners and mechanics encounter.

Figure 1. VTS Handlebar Pushbuttons Figure 2. VTS Analog Gauge

This article answers some important questions about the VTS system and its repair.

Here are the questions, the answers follow.

1. What is causing the repeated VTS failures?

2. How do I remove the VTS from the boat and reinstall it?

3. Can the black box be tested? How do I test it?

4. How do I test the motor?

5. How do I test the gauge?

6. How do I test the wiring in the boats harness to see if power is getting to the VTS? And how do I test the pushbuttons on the handlebar?

7. Is there a simple troubleshooting chart that I can use to determine what is wrong?

8. What is causing the fuses to blow?

9. Can problems with the VTS box create problems elsewhere in the PWC?

10. What can owners and riders do to prevent or minimize the problem?

11. Is the VTS black box repairable?

12. How much will it cost to repair the black box?

13. Is Bombardier doing anything about the problem?

14. How does this system actually work, and what did Bombardier have in mind when this system was designed? Is there a schematic diagram of the circuit? What does the circuit look like?

Here are the answers to the questions:

1. Q: What is causing repeated VTS failures?

A: One of the primary causes of VTS failure is water entering the VTS housing and then getting into the motor and its gearbox. Any water in a DC motor of this type is bad, salt water is really bad. A wet motor will corrode internally and potentially lock. This will cause the motor to overload the circuits in the VTS box. Salt water will directly short circuit the motor and overload the VTS box. The electronic portion of the VTS is located in a second box and is encapsulated in a flexible material similar to silicon. Water rarely gets to the electronic circuit board, but it is possible. Water in the VTS is bad.

Figure 3. VTS Box Installed in Bilge Figure 4. VTS Motor

Water gets into the VTS because the rubber boot on the stern of the boat somehow gets punctured. Usually it is punctured by the metal worm drive clamps that hold the boot in place. It is easy to over-tighten them and break the boot. Also, if they are too loose they will let the boot leak.

Sealant 1-5/16 Nut Worm drive clamp Boot Sliding shaft

Figure 5. Boot Assembly

Water could also get into the VTS box from inside the boat if the boats bilge was flooded and the gasket on the VTS box was faulty. Humidity could enter the VTS housing if the gasket is bad. But the most likely cause of water entry is from a faulty boot.

Figure 6. VTS Box Potting compound

There appears to be a failure of the potting compound that is used to encapsulate the VTS printed circuit board. This is a major cause of blowing your 7.5 amp fuse. The potting compound is intended to be an electrical insulator, but after a period of time it allows a conductive path to develop between the positive and negative power wires that feed the VTS board. This puts a continuous drain on the PWC battery and puts a continuous load on the 7.5 amp fuse. The area that appears to be causing the problem is around the varistor RV1 that is located between the up and down relays K1 and K2. There may be some other problems that cause the unwanted conductive path to develop. The encapsulation may be degrading when it is overheated by the copper electrical conductors on the printed circuit board. This situation could occur if water has entered the trim motor and caused it to lock. The circuit could also overheat if an overtravel situation develops. Overtravel will be discussed later. An analysis of more VTS boxes may help pinpoint the root cause of the problem.

Up Limit Switch (S1) Transistors Relay K1 Relay K2

Figure 7. VTS Circuit Board Gauge resistors Down Limit Switch (S2)

There are two limit switches that sense when the VTS is full up or full down (limit of travel). They are made of glass and are somewhat fragile. These switches fail in the on position. This is a major cause of VTS failures. One of these switches was found stuck on (closed) on one of the VTS boxes that was analyzed. If the up switch sticks on, it prevents any motor movement in the up direction. So if the rider trimmed full down, the trim could never be moved back up. The opposite situation would occur if the down switch sticks, the trim would eventually become stuck in the up direction.

If one of these switches fails open (off) when the rider is trying to trim full up or full down, the motor will continue to operate even though it is mechanically locked because the trim cannot extend or retract any further. This is a condition called overtravel. This overtravel condition could mechanically damage the screw threads on the sliding shaft and/or worm gear, making them subject to locking again later. An overtravel condition, or any condition that locks the motor would cause excessive current to flow in the motor circuit and would overheat components on the circuit board or the board itself. The heat could damage the potting compound and the relays. The glass limit switches are magnetically operated, and if the rider hit a large wave at the same instant he was trimming full down or up, the switch could momentarily open and allow overtravel to occur. Most circuits of this type would

simply blow the 7.5 amp fuse and would work properly again when the fuse was replaced. So the problem is more than just fragile switches. The switches are covered with a layer of duct tape before the encapsulation process. Corrosion was found on the switch leads even though the encapsulation was completely intact. Perhaps the adhesive on the duct tape is incompatible with the metal in the lead wires of the switches. The lead wires on these switches are ferrous and are probably somewhat subject to corrosion.

Water may be entering around the edges of the potting compound where it meets the plastic case of the VTS box. Water may also be entering at the points where the motor wires come out of the VTS box. However, none of the boxes analyzed showed any evidence of water penetrating the encapsulation.

It is also very possible that there were problems when the circuits were encapsulated at the factory. Moisture in the air when the potting compound was poured could cause problems. Impurities in or improper composition of the potting compound itself could be responsible for the problems. There is evidence of corrosion on some parts on the printed circuit board even though the potting compound was completely intact. The potting compound may be having a chemical reaction with the coating on some of the parts on the circuit board.

Relays K1 and K2 sometimes stick in one position, or develop stray electrical paths around their intended paths. The relay contacts are rated at 30 amps resistive load, but they are being used to switch an inductive load (motor) of about 3 amps. This should be completely adequate. There is a varistor installed across the motor to help protect the relay contacts. None of the analyzed relays showed any problems with the contacts. The relays are rated as being capable of being dropped from a height of 6.6 feet onto a concrete floor and still operate according to specifications. There is no clear reason why they should not work properly. They appear to be properly applied according to accepted engineering standards. They are made by Aromat which is a well known brand. They are sold as suitable for automotive and similar applications.

Any problems with the worm screw and the sliding shaft could cause an overtravel situation, or simply lock the motor down and burn out the VTS box. The system is electrically protected from overload by the 7.5 amp fuse. Be aware that fuses only protect the wiring from catching on fire. They do not protect the motor from burnout, nor do they protect the delicate electronics in the VTS box. If your fuses are blowing, there is a pretty serious problem. It would be nice if Bombardier had designed some electronic protection circuits into the VTS. Although, sometimes these protection circuits can cause a whole new set of problems. They can also be very confusing to troubleshoot. A 2 or 3 amp slow blow fuse would probably have been a better choice than the 7.5 amp automotive fuse.

There also may be other problems causing the VTS boxes to fail.

2. Q: How do I remove the VTS box from the boat and reinstall it?

The Bombardier Shop Manual contains a good description of how to do this. They have a lot of good illustrations. Its not hard to do, here is a summary.

VTS Removal:

Disconnect the battery.

On the outside of the transom, disconnect the ball joint on the link rod. Remove the clamps from the rubber boot. Remove the boot.

Ball joint nut Worm drive clamp Boot 1-5/16 Plastic nut Worm drive clamp

Figure 8. Boot and Sliding Shaft Lock nut, Adjustment Nut, Disconnect here

From inside the bilge, remove the VTS cover by pressing the three retainer tabs. Remove the four 10mm motor retaining nuts. Unplug the motor wires and remove the motor. Remove the worm gear and sliding shaft.

Press here. Retainer tabs

Figure 9. How to remove the VTS Cover

Figure 10. Motor 10 mm nuts Disconnect motor wires here.

Now, go to the outside of the transom and use a 1-5/16 socket with a long extension or Bombardier tool 295-000-133 to loosen the large plastic nut that holds the VTS box. If you have the Bombardier tool you can loosen the nut without removing the sliding shaft. Their tool is essentially a VERY deep well socket.

Figure 11. Bombardier VTS Tool 295-000-133

From inside the bilge, grab the VTS box and pull it forward and remove it. Trace the wires from the VTS box to their electrical connectors and unplug them. Loosen the cable ties that hold the wires to the hull as necessary to remove the entire cable lengths up to the connector plugs. There are two connectors (plugs) to disconnect. On SPX and some XP models there are three. Now you can remove the box and its wires.

VTS Installation:

The assembly procedure is essentially the reverse of the disassembly But here are a few things to look out for. Make sure the sliding shaft and the worm gear are in perfect condition and properly lubricated. Sea-Doo synthetic grease is recommended. Replace the worm gear and sliding shaft as a pair if there are problems with either. On some models (mostly SPX) there is a collar on the round tube that extends out of the back of the VTS box. If you have this collar, make sure that you remove it from your old VTS box and put it on the new box before you install the box through the transom. It is a good idea to chamfer (round off) the sharp edges on the sliding shaft where it goes into the boot. This will reduce the chance of damaging your new boot when the sliding shaft is inserted. Use a good marine sealant to seal the gasket and area where the VTS goes through the transom. When replacing the round gasket seal on the large plastic nut, use sealant and make sure the lips on the gasket are facing the hull. 3M Marine Adhesive Sealant 5200 works well and can be removed if you need to change the VTS box again. This sealant takes a long time to dry, up to several days, so plan ahead. Torque the large plastic nut to 10 ft-lb.

Figure 11. VTS Box with collar for SPX and some XP Models Collar

Make sure you match up the colors on the wires when you connect the motor. The connectors are made so that you can only connect them if they are matched properly. But if you did get them backward you will run the trim in the wrong direction and the motor will not stop at the end of the trim travel. Something will then be destroyed. Install the ball joint to the sliding shaft. Check that when the VTS is full up that there is 0.039 clearance between the nozzle and the venturi. See the Sea-Doo Shop manual for details on this adjustment. If you have too much clearance you will loose top speed. If you have less clearance you will go faster, but your nozzle could hit the jet venturi and cause steering problems or VTS problems. The spec of 0.039 is for a 96 SPX. Other models may have a different spec. Check your manual.

3. Q: Can the black box be tested? Can the up and down glass limit switches be tested. How do I do it?

A: Yes! The box can be tested with a multimeter which is a tool that is required for almost all electrical and electronic work. Any good quality analog multimeter will work, but a digital multimeter (DVM) is easier to use. Do not use extremely inexpensive analog meters, because they often put up to 9 volts into the circuit being tested when used in the ohms test setting, and can burn out fragile transistorized circuits. The Sea-Doo service manual gives a good test procedure for the trim gauge sending unit. But this is only part of the VTS box and is not the part that typically causes problems. They even admit that their test does not guarantee that the VTS box is in perfect condition. It sounds like the person who wrote that test was intending to complete the writeup but went out to lunch and never came back.

VTS Box Test Procedure Summary

This is a test for the wires going INTO the VTS black box. The box does not have to be removed from the boat. Disconnect the battery and unplug the VTS cables.

Power wires: (Step A)

Red/purple to black wire = infinite resistance in both directions. It should read at least 1 Meg ohm. This is a critical measurement, if it is between 1 Meg and 10 K ohm, you may be able to use the VTS box but it has begun to fail and will be running down your battery. Less than 10 K, get a new box.

Purple/white to black wire = 10 k ohm in both directions when the trim is in the middle point or with the sliding shaft removed. It should read about 5K to 6K if the trim is in the full up or full down position. You should be able to see the change in resistance when the trim reaches full up or full down.

Purple/white to red = infinite resistance in both direction.

Pushbutton wires: (Step B)

Blue/white to black wire = 32 k ohm in both directions.

Green/white to black wire = 4 m ohm or infinite, depending on polarity.

Blue/white to green white = 4 m ohm or infinite, depending on polarity.

Gauge sending unit wires: (Step C)

Brown /white brown/black = 24.3 ohm (+/- 20%) with VTS down, 171.3 ohm with VTS up. With VTS in between, the resistance should be between 24.3 and 171.3 ohms, in steps of 14.7 ohms.

Motor wires: (Step D)

Green/orange to blue/orange = 0 ohms in both directions.

Figure 12. Connectors SPX Model
Here are the details of the test:

Step A, Testing the Power Circuit and Limit Switches:

A-1. Disconnect all of the wiring from your VTS box. You do not need to remove the box from the boat. There are connector plugs on the wires that come out of the VTS box. The wires are quite long and the connectors are located in the front of the boat under the cargo compartment. Unplug both of them (3 on SPX and some XP models). Set your multimeter to the ohms setting. Be sure to connect your meter to the connectors (plugs) that go to the VTS box, not to the ones that go back to the boats wiring harness. Connect one lead of the meter to the black wire on the connector that has three wires. Connect the other meter lead to the red wire. The meter should indicate infinite resistance between these wires. A defective unit will typically read 180 ohms or less. If the reading is less than 10,000 ohms the box should be replaced. At 10,000 ohms the VTS will be draining the battery at one milliamp ALL THE TIME, even though the lanyard is removed. Less than 10,000 ohms will mean that the battery is running down even faster. 180 ohms will run the battery down in a few weeks or less if the boat is not operated.

Figure 13. Worm Screw Spin this to move trim.

A-2. Make sure that the trim system is not full up or full down. You may have to remove the motor and spin the screw with your fingers to get the trim to about mid point. Again with the multimeter set to ohms, connect the multimeter to the black and purple wires going to the VTS box. Put the red meter lead (+) on the purple wire. Put the black meter lead (-) on the black wire. The resistance should be 10,000 ohms, +/_20%. A very low resistance could cause a burnout of the boats computer module. A high resistance indicates that the VTS box will probably not work. A resistance of about 6.7 K ohm or 3.3 K ohms indicates that one or both of the magnetic limit switches are stuck (failed) in the on position.

Figure 14. Sliding Shaft w/worm removed. You can slide this to move trim up

and down.

A-3. Now you can test the operation of the full up and full down magnetic limit switches. Connect the multimeter to the black and purple wires like you did in step A-2 above. Move the trim rod (sliding shaft) to the full forward position. The resistance between the purple and black wires should drop from 10 K ohm to about 6.7 K ohm. You should be able to move the trim rod back to where it is not quite at full forward and the resistance should go back to 10 K ohm. Likewise when you move the trim rod to the full aft position, the resistance should drop from 10 K ohm to 6.7 k ohm. This test tells you if the two magnetic switches are working. These switches stop the motor from running when you reach full up or full down. Their proper operation is critical to the reliability of the VTS. If they fail to close when your trim reaches full up or full down you will have an overtravel situation probably blow the 7.5 amp fuse if you are lucky. If one of the switches sticks closed then your trim will only operate in one direction until the end of travel is reached and then the motor will stop. If you are not lucky, other bad things could happen.

Step B, Testing the Pushbutton Input Wires:

Next find the connector with the blue wire with white stripe and green wire with white stripe. These wires should go to the VTS box, not to the boats wiring. Connect the black meter probe to the black VTS wire. Connect the red probe to the green/white wire. The resistance should be about 4 meg ohm. Reverse the meter leads and the resistance should be infinite. Then connect the meter to the black wire and blue/white wires. With the red meter probe on the blue wire you should read about 32 K ohm. Reverse the meter probes and you should get the same reading. Significant deviations from these readings indicate problems with the VTS box.

Step C, Testing the Gauge Sending Unit Wires:

To test the operation of the trim gauge sending unit, remove the cover from the VTS box and disconnect and remove the motor. You will then be able to slide the trim rod back and forth manually. Connect your multimeter to the connector that has the two brown wires. Put the red meter lead (+) to the Brown wire with the white stripe. The black lead should go to the brown wire with the black stripe. Slide the trim rod forward and aft. The multimeter should go from 171.3 ohms (rod full aft) to 24.3 ohms with the rod full forward (full up trim). The reading should change in 10 or 11 distinct steps. Dont worry if your readings are off somewhat, 20% is probably ok. Just look for at least 10 distinct steps. You will have to move the rod fore and aft very slowly. If these readings are incorrect, the VTS box may still work, but the trim gauge will not work correctly.

Step D, Motor Wires:

Test the resistance between the wires that go to the motor. They are blue with orange tracer and green with orange tracer and are shown in Figure 11. The resistance should be nearly zero (2 ohms or less). If not, one of the relays is probably stuck.

4. How do I test the motor?

Step A

Disconnect the boats battery. Remove the oval cover from the VTS box. Disconnect the two wires that go to the motor (see Figure 10). Remove the motor by removing the four 10 mm elastic nuts that hold the motor in place. Connect the motor to a 12 volt battery and connect the multimeter in series with the motor. Set the multimeter to the amp setting. You can use your boats battery if you are careful, but use your buddys car battery if you are accident prone.

Figure 15. VTS Motor & Gearbox dissassembled (not recommended)

The motor should run and should draw about 1.7 amps. When the motor starts it should draw about 3.8 amps peak. If there is a mechanical load on the motor, it will draw more current. These readings are for the motor and its little gearbox connected together.

Do not remove the gearbox from the motor for this test.

Step B

Reverse the wires to the motor. The motor should run in the opposite direction. The amp readings should be the same in both directions.

If the motor current is over 2.0 amps there is probably binding in the motor or gearbox, or other problems. If the current is significantly higher in one direction, there is probably a problem with the gearbox. Typically the motors are fairly reliable. However, a motor that has been flooded with water caused by a leaking rubber boot could have problems. If you suspect the motor has been flooded with water, especially salt water, it would be smart to replace it. A good electric motor repair shop or an automotive starter shop might be able to repair the motor. This motor and gearbox looks a lot like an automotive windshield wiper motor. Dont forget to switch your multimeter off of the amp setting when you are done with the amps test.

Step C

The motor itself should measure 0.8 ohms resistance between the blue/orange and the green/orange wires (see Figure 20). The resistance from either of these wires to the frame of the motor should be 5 megohm or more.

5. How do I test the trim gauge?

Disconnect the sending unit connector plug on the VTS cable. It will have two wires, both brown. One brown wire will have a white stripe and the other will have a black stripe. With this plug disconnected, actuate the boats electrical system. The trim gauge should go full up when the timer is engaged. Connect a wire jumper between these two brown wires. The trim gauge should go full down. If the gauge passes this test it is probably ok.

If you really want to test it further heres how. Obtain three resistors, one 24 ohm, one 100 ohm, and one 171 ohm. If you cant get these values, use anywhere between 20 and 30 ohms for the first, 90 to 110 for the second, and 160 to 175 for the third. With the plug removed as described above, connect the 24 ohm resistor to the two wires that go back to the boats wiring harness. Activate the boats electrical system and the gauge should read full down or nearly full down. Remove the first resistor and connect the 100 ohm resistor. The gauge should read midpoint. Remove the second resistor and connect the 171 ohm resistor in the same way and activate the electrical system. The gauge should read full up or nearly full up.

6. Q: How do I test the wiring in the boats wiring harness to make sure that the proper power and signals are getting to the VTS box? How do I test the handlebar pushbuttons.

Step A

Disconnect the two connectors (three for SPX) as described in Question 2 . Set the multimeter to read DC volts. With the boats electrical system turned off, but the battery connected, connect the multimeter to the red wire and black wire on the connector plug that goes to the boats wiring harness. There should be 12 volts (battery voltage) between these two wires + red, - black. Any voltage other than battery voltage indicates a blown 7.5 amp fuse or a bad connection somewhere between the battery and your measuring point. Check for corrosion in the electrical box (fuse box). Check for loose red wire connections. Check for a blown 7.5 amp fuse.

Step B

Connect the voltmeter between the purple wire (+) and the black wire (-) on the connector plug that goes to the boats wiring harness. Activate the boats electrical system (timer). You should measure about 12 volts. You should actually get about 1.3 volts less than battery voltage as your reading. If you are not getting this, there is a problem with the electronic module, the MPEM, or the wiring harness, connections, or battery. A blown fuse to the electronics could be the problem also.

Step C

Now you will check the pushbuttons on the handlebars. Locate the connector that has three wires, Green w/white stripe, blue w/ white stripe and black. Unplug the connector and connect your multimeter to the wires that go back to the boats wiring harness (not to the VTS box). Set the multimeter to measure ohms. Connect the black probe of the multimeter to the black wire, and the red multimeter probe to the blue wire w/white stripe. You should read infinite resistance (ohms). Press the UP pushbutton. You should read nearly zero ohms. 1 to 2 ohms is fine. Repeat the procedure but connect the red probe to the blue wire w/white stripe. Again you should have infinite resistance. When you press the down button you should get less than 2 ohms. If you dont get these readings, you have a problem with your pushbuttons, or with the wiring to them.

7. Is there a simple troubleshooting chart that I can use to figure out what is wrong with my VTS without having a multimeter?

Yes, its not real simple but here it is. However the best way to diagnose the system is by using the tests in questions 3,4,5, and 6. This summary is provided to hopefully make things easier for the non-technical folks.

Simplified Troubleshooting Chart

Trim wont move at all when buttons are pushed and gauge is stuck. Check and or replace the 7.5 amp fuse in the electric box. Check the 5 amp fuse also. If the fuse blows again then most likely it is the VTS box. If the fuses blow, see the sections below on 7.5 amp and 5 amp fuse blowing. If the fuses dont blow, see if the system works. If the system works, carefully run it up and down, dont run it all the way to either end. See if the gauge works. If so run it up to the top. The motor should stop by itself. If it doesnt, then it may blow the 7.5 amp fuse and the VTS box is bad. Try the same test going down.

If the trim sticks when it gets to either end, tap the VTS box sharply with the handle of a screwdriver. A tap on the top or bottom is preferable to tapping on the side. This may dislodge a stuck limit switch. Then try to operate the trim.

Most of the time, VTS problems require replacement of the black box. Always check the sliding shaft and the gears and make sure they are in perfect condition. The definitive test for the VTS box is given in question 3.

Gauge stuck full up (trim works when buttons are pressed). Check for bad connections in the two brown wires to the VTS box. Make sure the connector is plugged in securely. With the connector unplugged, connect a jumper wire between the two brown wires that go to the boat (not to the VTS). If the gauge doesnt go down, then the gauge or wiring is bad. If it does, then the VTS box is probably bad. To make sure, run the gauge test described in question 5, and test the VTS box as described in question 3.

Gauge stuck full down (trim works when buttons are pressed). Unplug all of the VTS connectors. The gauge should go full up. If it does, the VTS box is bad. If not, check 5 amp fuse and power to gauge. There should be about 11.2 volts meas