Repairing Fuse Inside Fuel Sender Aluminum tube style, NO red lamp / Low Fuel warning

[D007]

Hi everybody!

Currently helping a buddy with his ski that has a broken fuel sender (no signal from unit), and would like to save on the cost of a new one. I was reading thru posts about how some people with some late 90's sea doos were repairing the fuse inside the fuel baffle by bypassing the fuse and hooking up an external fuse outside the fuel tank. Hadn't been any posts of any explosions or problems with the repairs.

Compared the two and they seemed pretty similar just different casings, boards inside almost identical and both in contact with the fuel. Figured i'd open up the sender on his to see if this was the problem after checking the resistance on the pink and black wires for the sender and finding open circut and checking at the mfd and finding no signal.

After probing around on the circut, there is a fuse at the top of the sender's circut board that was blown like in the posts i'd found for the seadoos. I bypassed with solder and hooked up an external fuse and fuel level worked perfect . Question is... Is this relatively safe to do?

It now has the enclosed fuse before going into the sender so it would be protected from spikes/surges/fuel vapor inside hull (enclosed fuse), etc so it would seem there would be minimal chance of an "incident" as would be the case without a fuse, and seeing how there are already electrical circuts in contact with the fuel. Basically just moved the fuse outside rather than in.

Fuse inside on his (and opened up mine to see if same) was a 1/8amp fuse on the board. 99 & 00 Slx's.

Just figured i'd ask to see if anybody has any input on this as I havent seen any posts dealing with this on the polaris skis. Seems on the other forum people have opinions going both ways.

Thanks for any input on the topic!

[K447]

Repairing the fuse inside the magnetic float type fuel senders, carb models 1995-2004

Could you post some clear photos of the repair and changes you made?

The repair you describe sounds reasonable. What Amp rating is your replacement fuse?

I have not seen any reports of Polaris fuel level senders which have failed due to a blown fuse.

The most common failure for Polaris fuel senders is the magnet float sinks, and always shows low fuel even when the tank is full. Replace the float and the sender works properly.
MFD Fuel level reads low, but the fuel tank is full

Perhaps other Polaris owners with failed senders have not realized they could bypass the internal fuse.

The important difference is that a sender with a sinking fuel float will still measure 240 ohms or less between the Pink and Black sender wires and the red MFD warning lamp will flash. This problem is corrected by replacing the internal float with a new float.

If the small fuse inside the sender fails then the ohm reading will be much higher than 240 ohms, probably reading an open circuit. The MFD will show nothing for fuel level, and the red warning lamp will not flash for Low Fuel. As you have described, an open circuit condition requires the original fuse to be replaced, or as you have done, bypassed and an external fuse provided inline with the Pink wire.

[D007]

He was having the problem of nothing showing up for fuel on the display. When i checked everything there wasnt a signal to the mfd and open circut when testing the blk/pink wires in e-box. Was pretty sure beforehand it wasn't the float because id had that problem on my 900 and there was still a bar on the mfd before replacing the float, he didn't have anything there and the display wasn't saying "fuel".

Im thinking the same that it should be good to go as everything seems protected, just moved the fuse.

The sender is already in the tank but im sure i can at least get pics of the fuse I put in before the pink wire goes into the sender, just gotta get over there to take pics.

Figured this could be good to share as it could help others with the same issue and save some cash vs cost of new whole unit. Guessing that there are probably a few other models with the same setup on the sender. Could probably make up a guide with pics and specifics when i get them. Just wanted to get some feedback on what others thought about the repair. Hadn't seen anything dealing with this and a polaris ski.

Thanks K447

[K447]

MFD display always shows Low Fuel - Sinking fuel float or blown sender fuse?

He was having the problem of nothing showing up for fuel on the display. When i checked everything there wasn't a signal to the MFD and open circuit when testing the blk/pink wires in e-box.

Was pretty sure beforehand it wasn't the float because id had that problem on my 900 and there was still a bar on the mfd before replacing the float, he didn't have anything there and the display wasn't saying "fuel".

... I can at least get pics of the fuse I put in before the pink wire goes into the sender...

Figured this could be good to share as it could help others with the same issue ... Guessing that there are probably a few other models with the same setup on the sender.

Could probably make up a guide with pics and specifics when i get them. Just wanted to get some feedback on what others thought about the repair. Hadn't seen anything dealing with this and a Polaris ski.

The same type of fuel level sender was used in almost all 1996-2004 Polaris carburetor models, and I think also in a few 1995 models. Differences between the various senders were mainly in the length of the metal tube (differences in fuel tank depth) and the number of hose nipples on top (Reserve+Main or no reserve on fuel selector valve).

The observation that the MFD acted differently with the open circuit (blown sender fuse) is useful. That can be the diagnostic observation that differentiates between a blown sender fuse and a sinking fuel float.

MFD always warns Low Fuel = replace fuel float
MFD fuel level is blank, with no warning about low fuel = repair sender fuse

Your contributions are appreciated. A tidy little 'How to' guide and photos would be great to have.

[D007]

I'll definately post some pics and details with a how to. Not sure if this would be the forum for it or not so i'll just add it on here. Below is a rough schematic of the board and a summary of the repair.

The view is the inside of the board - towards the center of the fuel sender.

The fuse was bypassed on the opposite-facing outward- side of the board that has the soldered circut paths, bridging the gap of where fuse's path would have been with solder. External, glass enclosed, fuse added to the pink wire above where the wire goes into the sender unit.

[K447]

... External, glass enclosed, fuse added to the pink wire above where the wire goes into the sender unit.

What Amp rating external fuse did you use?

A minor problem we have seen with the 1/4 Amp fuse (located inside the electrical box) for the MFD display is that the thin wire inside the fuse tends to be fragile.

I have never looked, but I expect we could find a source of replacement 1/8 Amp solder mount fuses for inside the sender.

[D007]

Bypassing Fuse Inside Fuel Level Sending Unit

This was the procedure to I used to fix a problem with the MFD not showing anything on the gas gauge. Would show full bars when the MFD was "woke up" but went blank after that.

If the fuel gauge is showing empty or 1 bar and saying Low Fuel, most likely a fuel float replacement would be needed. This procedure will NOT fix those issues with the MFD fuel reading.

If you suspect the fuel sender is broken it would be necessary to check the resistance between the pink and black wires to the sender from the e-box. If there is no resistance and a short or open circuit is suspected check the wires and connections first before attempting to bypass the fuse inside the fuel level sending unit.

This was done on a 99 SLX and I also checked to see if my 00 SLX had the same fuse and they were both the same, so I'm guessing there are other non fuel injected models with the same sender.

Working with fuel/fuel tank = NO SMOKING or OPEN FLAMES!!
This worked for my particular situation and may not be the cause of yours as there could also be damaged resistors in the circuit that could cause this also. I read about this being done on a sea-doo and the circuit board appeared very similar to the ones on my buddy's SLX so i figured I'd investigate and see if same would apply to the Polaris'.
Not responsible for any damage.


1. Mark and remove the fuel lines from the sending unit, then remove the screws holding the sender to the fuel tank

2. Take out the fuel sender from the tank. Remove the nut and washer on the bottom cap of the sending unit. I used a 9/32 socket. Careful to catch the washer after the nut comes off.


3. To remove the top of the sender with the board I had to gently tap the flange on top of the unit that mounts it to the fuel tank. Gentle taps and it came off pretty easy. Pull out the top with circuit board attached.

4. On the side of the board that has the resistors and magnetic sensors there should be a fuse at the top labeled F1. This was the fuse on my friends SLX that was blown causing the MFD to not have a fuel reading (and there was no 'Low Fuel' message).


5.You now have two options, try to find an appropriate replacement fuse (the ones on his and mine were 1/8 amp fuses) or bypass the fuse. I bypassed the fuse and installed an external sealed fuse just outside the sending unit.

To bypass the fuse I soldered a connection on the reverse side of the board where the soldered circuits are, parallel to the fuse on the opposite side. Then clipped out the fuse and soldered the small tips where the fuse went through. Did the connection on the reverse side just because the other soldered circuit paths were on that side and would be farther away from the inside metal casing. Tried to have a nice path that was not sticking up any farther than the other solder points on the board.


6. I Let the solder dry completely then reinstalled everything in the reverse order of removal. May have to tap gently to get the board and top back on the metal housing. When putting in the float the metal tabs face towards the center of the unit. Also when putting the washer and nut on, don't overtighten or the stud on the circuit board may break off and cause a whole new problem.

7. After the sending unit was reinstalled, I soldered in an enclosed fuse holder on the pink wire going into the sender, fuse holder was rated for marine use.

If you can find a 1/8amp fuse that would be an exact match for what was in the unit. I used a 1/4amp glass encased fuse as that was the smallest enclosed fuse i could find locally for testing purposes, but ordered him some 1/8amp fuses online that will be swapped out with the 1/4amp. Don't think that small of increase would cause any problems but wanted to get him some of the 1/8amp fuses to be sure. Checked at a local radio parts supply store and they had the circuit board fuse, but I wanted to have the fuse easily accessible if the problem ever occurred again.
Wrapped the end that opens/separates for the fuse to keep any water from sneaking in the fuse holder and still leaves easy access if fuse blows in the future.


Tested it out a few times and everything is now functional with the fuel gauge on the MFD. Basically just moved the fuse that was inside, outside.

Hope that this info is useful to someone out there, good thing to check before buying a new unit or when troubleshooting the issue of no signal for the fuel gauge/blank fuel gauge.

[K447]

Good job! It is good to have the repair process so nicely documented.

As far as I know, these fuel sender fuses don't fail very often.

Your repair method with the external fuse holder looks just fine, but if I was fixing my own sender I think I would just directly replace the tiny fuse on the sender board with another new 1/8 amp fuse. That would keep the sender wiring looking factory original, which would be my own preference.

Either repair method will work, of course.

For others who need their sender fuse repaired, any local electronics repair technician should be able to replace the original small fuse and solder in a new fuse in a few minutes.

Originally I thought that you would need to first remove the aluminum sleeve from the circuit board (as described by D007) and just take that to the repair shop.

Given further thought, the replacement axial lead fuse can simply be soldered to the back side of the circuit board with the board still in the sender. No need to disassemble the sender at all. The solder traces on the back side would need to be gently cleaned first, then just solder the replacement fuse in place to the circuit traces where D007 shows his solder bridge. Once repaired in this manner, there is no need for an external fuse holder as the repaired sender will work just like a factory unit.

Any competent electronic repair shop should be able to handle this repair in short order. The only question would be whether they have the appropriate small replacement fuse on hand.

The replacement fuse that would fit right on the sender circuit board would be something like Digi-Key Part Number 507-1005-ND

These axial lead fuses are physically quite small, and don't even look much like fuses.


Note: photo happens to be a 3/8 Amp fuse, but the sender requires 1/8 Amp fuse

[heebeha]

How did you test to see if that F1 fuse was blown?

It looks ok and mine looks ok too.

[K447]

How did you test to see if that F1 fuse was blown?

It looks ok and mine looks ok too.

Ohm test the fuel sender after disconnecting the wires from the electrical box.

If the ohm reading is below 300 ohms (approximately) then the fuel sender fuse is good.

An ohm meter reading across the sender wires that is way too high (way way higher than 240 ohms) or an infinite ohm reading suggests there is a broken wire or the sender fuse is blown.

[heebeha]

I soldered a wire between the fuse connectors on both sides and added an exteranl fuse from radio shack with a .312 fuse. She is working again YEAH. Great help here. Thank you.

[dajson]

Removing sending.

I can't remove the sending unit . It comes almost all the way out but end of tube seems to have a flange so it blocks it from coming out of tank.

Bypassing Fuse Inside Fuel Level Sending Unit

This was the procedure to I used to fix a problem with the MFD not showing anything on the gas gauge. Would show full bars when the MFD was "woke up" but went blank after that.

If the fuel gauge is showing empty or 1 bar and saying Low Fuel, most likely a fuel float replacement would be needed. This procedure will NOT fix those issues with the MFD fuel reading.

If you suspect the fuel sender is broken it would be necessary to check the resistance between the pink and black wires to the sender from the e-box. If there is no resistance and a short or open circuit is suspected check the wires and connections first before attempting to bypass the fuse inside the fuel level sending unit.

This was done on a 99 SLX and I also checked to see if my 00 SLX had the same fuse and they were both the same, so I'm guessing there are other non fuel injected models with the same sender.

Working with fuel/fuel tank = NO SMOKING or OPEN FLAMES!!
This worked for my particular situation and may not be the cause of yours as there could also be damaged resistors in the circuit that could cause this also. I read about this being done on a sea-doo and the circuit board appeared very similar to the ones on my buddy's SLX so i figured I'd investigate and see if same would apply to the Polaris'.
Not responsible for any damage.


1. Mark and remove the fuel lines from the sending unit, then remove the screws holding the sender to the fuel tank

2. Take out the fuel sender from the tank. Remove the nut and washer on the bottom cap of the sending unit. I used a 9/32 socket. Careful to catch the washer after the nut comes off.
[ATTACH]234347[/ATTACH]

3. To remove the top of the sender with the board I had to gently tap the flange on top of the unit that mounts it to the fuel tank. Gentle taps and it came off pretty easy. Pull out the top with circuit board attached.

4. On the side of the board that has the resistors and magnetic sensors there should be a fuse at the top labeled F1. This was the fuse on my friends SLX that was blown causing the MFD to not have a fuel reading (and there was no 'Low Fuel' message).
[ATTACH]234348[/ATTACH]

5.You now have two options, try to find an appropriate replacement fuse (the ones on his and mine were 1/8 amp fuses) or bypass the fuse. I bypassed the fuse and installed an external sealed fuse just outside the sending unit.

To bypass the fuse I soldered a connection on the reverse side of the board where the soldered circuits are, parallel to the fuse on the opposite side. Then clipped out the fuse and soldered the small tips where the fuse went through. Did the connection on the reverse side just because the other soldered circuit paths were on that side and would be farther away from the inside metal casing. Tried to have a nice path that was not sticking up any farther than the other solder points on the board.
[ATTACH]234350[/ATTACH]

6. I Let the solder dry completely then reinstalled everything in the reverse order of removal. May have to tap gently to get the board and top back on the metal housing. When putting in the float the metal tabs face towards the center of the unit. Also when putting the washer and nut on, don't overtighten or the stud on the circuit board may break off and cause a whole new problem.

7. After the sending unit was reinstalled, I soldered in an enclosed fuse holder on the pink wire going into the sender, fuse holder was rated for marine use.

If you can find a 1/8amp fuse that would be an exact match for what was in the unit. I used a 1/4amp glass encased fuse as that was the smallest enclosed fuse i could find locally for testing purposes, but ordered him some 1/8amp fuses online that will be swapped out with the 1/4amp. Don't think that small of increase would cause any problems but wanted to get him some of the 1/8amp fuses to be sure. Checked at a local radio parts supply store and they had the circuit board fuse, but I wanted to have the fuse easily accessible if the problem ever occurred again.
Wrapped the end that opens/separates for the fuse to keep any water from sneaking in the fuse holder and still leaves easy access if fuse blows in the future.
[ATTACH]234349[/ATTACH]

Tested it out a few times and everything is now functional with the fuel gauge on the MFD. Basically just moved the fuse that was inside, outside.

Hope that this info is useful to someone out there, good thing to check before buying a new unit or when troubleshooting the issue of no signal for the fuel gauge/blank fuel gauge.