7.5 amp fuse burns instantly

[Evan_Docotrian]

Hello. This is my first post on the forum. I could not find my specific problem anywhere. I was out on the water the other day when my VTS on my 1996 seadoo xp 800 stopped working. I've tested the VTS motor to find it works like it should. I traced the problem to a burnt 7.5 amp fuse in the black box in front of the battery. All I had on hand was a 15 amp fuse so I decided to throw it in just to see if that's the problem. As soon as I put the fuse in I smelt burning electrical so I pulled the fuse out and looked at it and it had already been burned in two (note the ski was off and the key was out). I tested the battery and the hot wire that goes to the fuse and they both had the same reading on my multimeter. Y'all got any ideas where my problem is?

I appreciate the help - Evan

 

[etemplet]

Not sure where your problem lies but if you keep messing with that 7.5 amp fuse people say it will burn out the MPEM. I'd check the grounds. You likely have a bad control box in the rear of the ski. Check the connections up front for shorting. Might be the switch. Gotta find the problem or it can do serious damage. Personally I don't like the trim on any of the skis but I understand people like to stunt them and such. For me I could just set the trim in the middle and disconnect everything. Good Luck !!

 

[Evan_Docotrian]

Not sure where your problem lies but if you keep messing with that 7.5 amp fuse people say it will burn out the MPEM. I'd check the grounds. You likely have a bad control box in the rear of the ski. Check the connections up front for shorting. Might be the switch. Gotta find the problem or it can do serious damage. Personally I don't like the trim on any of the skis but I understand people like to stunt them and such. For me I could just set the trim in the middle and disconnect everything. Good Luck !!

Thanks for the help that's what I was planning on doing but everything on this ski is mint and the VTS worked great until it suddenly didn't so i thought id give fixing it a shot. If it come down to just setting the trim manually is there a proper way to disconnect everything in regards to the VTS?

 

[etemplet]

I believe just leaving the fuse out is sufficient. On a side note it was a really really bad idea to put that 15amp fuse in there but looks like you did no harm. I've read some bad stuff about Trim issues and MPEMs. Just be careful. Sometimes you can find a donor ski with the trim box working. Your trim motor might be working but drawing too many amps. Was it wet in there? That boot on the back of the ski gets dry rot and lets water into the motor section. Good Luck.

 

[Evan_Docotrian]

I believe just leaving the fuse out is sufficient. On a side note it was a really really bad idea to put that 15amp fuse in there but looks like you did no harm. I've read some bad stuff about Trim issues and MPEMs. Just be careful. Sometimes you can find a donor ski with the trim box working. Your trim motor might be working but drawing too many amps. Was it wet in there? That boot on the back of the ski gets dry rot and lets water into the motor section. Good Luck.

Yes I figured it wasn't the best move after I did it. When I pulled the cover off the VTS motor housing earlier there was water in the motor area. Thats why the first thing I did was hook the motor directly to a battery to make sure it still works.

 

[Evan_Docotrian]

If its the motor would it be safe to disconnect it and put a 5 amp fuse in place of the 7.5 amp and test the 2 wires that connect to the motor to see if I have power there?

 

[etemplet]

If it had water in it your motor likely needs to be replaced or at least dried out. Those are not too expensive used. I don't think your idea would be an issue as you're only checking power TO the motor and not trying to operate it.

ALSO replace the rubber boot to keep water out of there.

 

[Evan_Docotrian]

Ok, I did my little test this morning. Leaving the ski off and the key out I unplugged the 2 wires that go to the VTS motor, put a 5 amp fuse where that 7.5 should go. Without pressing any buttons on the ski I watched it physically pop and blow the fuse in about 3 seconds. So are we thinking I need to check and clean all my grounds next? I cleaned them all at the start of the season so they should be pretty shiny. With that being said I changed the battery about a month ago and could have messed something up then.

 

[etemplet]

Download the repair manual and look at the wiring diagram. If the fuse is blowing something is drawing a lot of current. Might have an issue with the VTS block. They go bad. I'd check those wires going to the Block. Should be easy to isolate. You're on the right track.

 

[jim downing]

Gene I have rebuilt several of the VTS modules. It is a bit of a job but possible. I suggest you unplug the 6-conductor plug that runs from the MPEM to the VTS unit and the 2 conductor plug (black and red/purple) that also runs from the MPEM to the VTS (the latter is hot all the time). Now there should be no load on the VTS circuit. Put in a new fuse and test it again. If the fuse blows then you have a serious MPEM problem or there is a bare and shorted wire somewhere between the MPEM and the connectors. Hope for a shorted wire. Otherwise, if you are familiar with the circuit diagram for your model you will see that the conductors in the MPEM are basically pass through and you can wire around the MPEM. It is a bit messy but possible and much cheaper than buying another MPEM. If the fuse does not blow then you know the problem is in the VTS unit. In that case unplug the two wires inside the module going to the motor and try again. If the fuse blows either with or without toggling the up/down switch then there is a short inside the potted circuitry (probably due to a bad relay). If the fuse does not blow then the motor is probably shorted. Reconnect the motor, put in a new fuse and see what happens. Note, you can test the motor by putting clip leads on the motor pigtails and hooking them directly to the battery. If it runs clockwise then flip the clip leads to see if it runs counter clockwise. If it does not run you can either buy a new motor (easy to find on Ebay or try to fix the one you have) If it filled with water then it is probably frozen up and can be cleaned and made to work again. I will provide more assistance if you still have questions.. Jim

 

[etemplet]

<snip> Otherwise, if you are familiar with the circuit diagram for your model you will see that the conductors in the MPEM are basically pass through and you can wire around the MPEM. It is a bit messy but possible and much cheaper than buying another MPEM. again. I will provide more assistance if you still have questions.. <snip> Jim

I'm not the original poster but I'm curious where you find these circuit diagrams? I have a few MPEMs I'd like to fix for sure.

 

[jim downing]

Are you referring to my comment about wiring around the MPEM?

You can find most of the Seadoo manuals at SeaDoo Manuals - FREE PDF Download! . At the end of the service manual you will find the main circuit diagrams for your Seadoo.

This is how the VTS unit works: There is a low current circuit that activates two relays that route the high current 12v (red/purple & black) to the motor. When the toggle switch is set to UP then the UP relay is activated and the motor pulls the plunger in. As the plunger goes in a magnet passes over a series of small magnetic switches, each attached to a resistor of increasing ohms. When the motor has driven the plunger up to a certain point, the last magnetic switch deactivates the relay, thus preventing overrun. When the toggle is moved to Down, the Down relay is activated sending current in the opposite polarity to the motor. As the plunger moves out the magnet activates one magnet switch after another each time sending a decreasing voltage (via purple/white wire) back to the console display. When the plunger reaches the last magnetic switch the relay is deactivated to prevent overrun. This logic is powered by 12v sent to the VTS module from the MPEM via the green/white wire.

Test MPEM circuitry: (1) make sure the red/purple wire is hot (red oval) all the time. If not disconnect the 2 wire connector and run a clip lead from red/purple wire to the positive side of the battery and a clip from the black wire to the negative side of the battery. Test.
(2) make sure the green/white is hot. This wire powers the logic in the potted VTS module. Hook a test lamp to ground and the the green/white wire from MPEM. Put security key in. Light should stay one till the MPEM times out. If not, run a hot wire from battery to the green/white wire and test the VTS. If that fixes the problem, you can tap into the MPEM 12v circuit by splicing into the purple wire that powers the instruments. See the green ovals. To test the UP/DOWN toggle circuit disconnect the 6 pin connector and run a clip lead from the positive side of the battery to the brown/black wire from the MPEM. Hook your test lamp to the brown/white and ground. Press the up/down switch. The light should turn on in one position or the other. Hook your test lamp to the black/white and ground. Press the up/down switch. The light should turn on in one position or the other. If not, you can wire around the MPEM by cutting and splicing the wires in the pink ovals.

If the MPEM circuits check out and the VTS still doesn't work then you most likely have a failed VTS module. Usually this can be repaired but it is a major task getting the PC board out without destroying it. Even then I would not recommend trying to do this unless you know how transistor switching logic works. My experience has been that the switching logic is usually ok and the fault is in the board itself or the relays. Water can get below the potting material and cause the small conductors to corrode or a high current relay gets struck. When that happens the motor drives the plunger to its limit and cuts off power.

The second attached photo shows one of the VTS units I rebuild. After I fix the logic I put the PC board back in the box and line the box with a kitchen plastic wrap. I then pour a layer of clear epoxy and let it dry. This provides a tight fitting new cover for the PC board. I seal it with RTV. Not the prettiest thing but it works.

If you need additional help, please ask. Jim

 

[etemplet]

yes I know where those drawings are located. Thanks. Prices on these MPEMs are absolutely insane along with everything else plus.... I love a challenge. "D