95 SN Fuel Sending Unit problems |
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CrazyCanuck
Senior Member Joined: July-21-2013 Location: Vancouver B.C. Status: Offline Points: 254 |
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Posted: May-25-2014 at 3:40pm |
I just did my sending unit the other day. In my case it was the sending unit. I touched the 2 wires that connect on top of the unit to confirm the gauge and wiring were okay. ( the gauge should peg to full when wire touch)
Then I took apart the sending unit and repaired the broken wire. The little hair like wire that is wrapped around the board that becomes the resistor was broken right at the rivet where it connects to the black internal wire. I had to drill the rivet and use a small machine screw and nut to rebuild it. I was very happy to have been able to fix it. I wish I had taken pics....sorry. |
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https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcRtW3vJrMHLdqBzndt9VX3oOpBuRopGlzKq9Ea7pAO7wnTuoD8E8g
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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It looks like a new thread was started with the final outcome:
It was the Guage |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Run a separate wire to a known good ground and make sure it's grounded to the sender not to a screw on the sender. If you have to even hold it there to test that's fine. See what than happens. I had grounded to the screw on mine with a metal tank,it did not work,I ended up soldering a ground to the sender itself. Some senders have a separate ground lug.
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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There should not be any voltage on the pink,that would very dangerous having that going right into the tank. The gauge will have 12v but the pink will just have the resistance to ground on it. If that's what is going on there is your problem,but if your confusing your terminology all bets are off.
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JB1995Ski
Groupie Joined: July-22-2013 Location: SE Georgia Status: Offline Points: 60 |
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Brian,
A picture is worth a thousands words!!! No, my set-up was not like what you submitted. The green wire used to connnect to the ground terminal on the sending unit was spliced from a black wire up underneath the stern, but there is another green wire back by (for) the stern light. I was having a hard time trying to understand how the circuit works as it was wired. I had a pink (12v) and a green (spliced w/black) to the grounding tab. Originally, that ground wire split off and went to a screw on top of the gas tank. There are not two separate ground wires, but there will be come Friday. Thanks! |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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Hold off on buying a new gauge...
Does your wiring setup look roughly like this?: http://www.correctcraftfan.com/forum/uploads/6518/Sender.JPG That pink wire is the sender wire. The black is/should be ground to either the engine block or the dash ground or the battery. The shortest and best route would be just the engine block if you're adding new. I believe the green is the ground for the stern light. It may also ground the fuel filler neck. A fuel gauge works the same as the temp gauge and oil pressure gauge. The gauge itself is essentially an Ohm-meter and the sender just provides variable resistance to ground, the engine block. The gauge reads that change in resistance. Of course, in the case of the fuel gauge, the engine block isn't nearby, so that metal ring is essentially "the engine block", the thing is, that ring needs to be grounded to the block. So, if that black wire is sketchy or loose, your not going to get a good ground. If you're blue lighting wire is hitting anything in the vicinity, that's going to screw up your whole deal! That's essentially carrying un-metered positive intended for your stern light. Before you chuck money at a fuel gauge, at least post a pic of how you have your sender wired. Also, run an additional ground from the metal ring/tab direct to your block, and see if that helps things. |
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JB1995Ski
Groupie Joined: July-22-2013 Location: SE Georgia Status: Offline Points: 60 |
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WEEKEND RESULTS:
Not favorable for this boat owner. The only thing I didnt do in this thread was continuity checks of the wires. The gage deflects to full with 10-12vdc. Returns to empty with one or both leads disconnected. Switched leads, same result. Connected both leads, same result. Connected sensor directly to gage with separate leads, same result. Connected DMM to the sensor leads and raised/lowered arm, resistance was good and read 30-246 ohms. Did the same with sensor connected directly to gage with the separate leads, no gage deflections, full with wires connected, empty with one or both wires disconnected. Wires to the gage: pink-line in; black-ground, purple-safety switch circuit; lt blue-illumination. None of the wires appear to be out of place by looking at the other gages. I'm going to order a new gage to see if it's that. |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21184 |
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After checking to make sure you dont have a gauge/sender mismatch, I'd clean the connections and test for continuity from front to back. If that checks out, I'd probably disconnect the wires entirely and run a few test ones to see if behavior returns to normal. If it does, you know youve got an issue in the wiring somewhere.
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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240 to 30 should work great if that is your gauge. I don't know the years that they changed from American Standard to European Standard.....or the PO replaced the gauge with the opposite type (that would be overly messy).
It would be really strange for it to be a wiring harness issue if the gauge works "generally" but perhaps not "accurately"....."Accurately" suggests gauge/sender mismatch or bad sender resistance. Once you are at the boat, remove the sender, attach the wires and play with the float. If it moves the gauge generally in the right direction, you are OK..... if it's generally backwards you have a gauge/sender mismatch. Hey Zach/Townsend/GodFather - When (What years) did the fuel gauge resistance specs change? |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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BTW - the need for a wiring diagram is probably moot. The gauge is your multi-meter. If it does anything that I didn't specify in the troubleshooting, you have a wiring issue.....then go mucking with dash wiring (yuk!).
If it behaves in the ways listed, get the right sender..... |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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Also, clean off your tank top VERY WELL before removing the old sender. All that crud, your old broken gasket pieces, screws and nutdriver WILL FALL into your gas tank hole.
Be very intentional and clean - IT WILL HAPPEN! You have been warned...... |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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BTW - the need for a wiring diagram is probably moot. The gauge is your multi-meter. If it does anything that I didn't specify in the troubleshooting, you have a wiring issue.....then go mucking with dash wiring (yuk!).
If it behaves in the ways listed, get the right sender..... |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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For WEMA senders, you measure the distance from the bottom of the tank to the top of the tank (through the hole) then subtract for clearance (On the site they mention subtract 1 inch for SSS/SSL type).
Art may have one the right length...if not, order from WEMA and mention my name - Steve Karras -and CCFan for a discount (That's right, I'm kinda a big shot with WEMA). |
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JB1995Ski
Groupie Joined: July-22-2013 Location: SE Georgia Status: Offline Points: 60 |
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Kris, Steve, Peter:
Thank you all for the information you have provided. The boat is at my in-laws, covered in a barn so I can't get to it during the week right now. So as not to put anybody on report, I am asking for recommendations on where to get a replacement sending unit vice telling you where I bought my current one. The replacement unit came with no paperwork, no tech specs or instructions. Since I ran out of gas on my first endeavor in the middle of a river, I assumed it was the sending unit. The gage would deflect from empty to full after turning the ignition switch. I thought this would be a quick fix. So, here are some answers to your questions: Without tracing all the wires and NOT having a wiring diagram for a 95, I will have to figure out the lighting circuit and see if it's crossed. My next course of action is do all the things you guys have mentioned. I am going to check continuity on the wires from the gage to the sending unit, as well. I did not think to check the resistance band of the new unit, but I will. I will have to look at the sending unit to find out what type, brand and the specs are for it. I willing to bet I will not find the answers to that by looking at it. Steve, I checked out the WEMA page, how far do I measure down for the length of the float arm? 2-4 inches from the bottom?? |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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JB,
Both Kris and Steve told the story about checking the fuel gauge. Kris touched on using a DMM to check the resistance which is the best way to tell if the sender is bad. Did you? Did you do any diagnostics? Did you check the correct sender ohm range? You should have asked us first before replacing the sender! |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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This works on boats up to 93, that I know. Pretty sure it holds true for 95:
Quick check - With power off, pull a wire off the sender. Good gauge should NOT move. With power on, pull a wire off the sender. Good gauge should drop from the level it was reading to 0. With power on, touch one wire to other wire. Good gauge should peg full and stay pegged at full. If all that shows a good gauge, make sure you have the correct sender (Probably don't).... you want an SSS/SSL Standard American 240-33 ohms sender.... NOT a European standard (0-180 ohms) which is what many later boats use. As everyone here knows, I like the WEMA fuel senders. Check out the thread I started and Art took the wind out of...... check out www.wemausa.com Steve |
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Dreaming
Platinum Member Joined: May-21-2010 Location: Tacoma, WA Status: Offline Points: 1870 |
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Well, here goes... from my understanding of the system,
I think you have a mismatched sending unit, or the whole deal is mis-wired. The sender is a variable resistor that changes with the position of the float. The gage should be getting a variable voltage based on the changing resistance If the resistance is wrong at the sender, the voltage returned to the gage will be wrong. Or, if the gage has a direct 12v connection, instead of a variable voltage to the input terminal, the gauge would read full when it gets power. Is it possible that the lighting circuit is crossed up with the input circuit? |
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JB1995Ski
Groupie Joined: July-22-2013 Location: SE Georgia Status: Offline Points: 60 |
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I recently replaced the float/sending unit because my fuel gauge always drifted to full upon turning the key. I found this out the hard way on my 1st trip out after purchasing last summer. Removed the old and matched/trimmed new to same length and re-installed. There were 2 wires attached; a red wire to the center post and a green wire attached to the tab (ground) and it was also spliced to another green attached to a bolt on top of the gas tank unit. Fuel gauge does the same thing with the key turned on and if I removed the green wire it slowly drops to empty. The tank is approx half full just from looking at it.
I guess I need to check continuity of the wires and make sure I have 12vdc coming from the green and red wires. Other than that, I am assuming the gauge is good based on its delflections. Any suggestions? |
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