fuel sender replacement

[gwp]

88 model #568
Looked around site but can't find info to determine if fuel sender can be replaced without removing tank. Testing indicates sender has failed. Any help appreciated

[Ron Hill]

gwp : Look in the Mainsheet tech notes and /or WiKi and you'll find I wrote an article on replacing a fuel sender on my 1988 C34!!

[gwp]

Thx Ron....i saw your article but you had removed your tank which I did way back as well. Wondering if the sender can be replaced without removing that monster again. I see Catalina direct has a new style sender which doesn't feature the long elbow float but has a vertical action float. This might just slip in thru inspection plate in port lazerette???? Thx

[Stu Jackson]

gwp, the Beckson plate holes above the fuel tank sender in the port locker have reportedly been placed in different location through the years, one skipper said his was nowhere near enough to the top of the sender/fuel supply to even allow him to reach the fuel shutoff valve.  Since you have your boat right in front of you, the only suggestion I can make is to check how it is located on your boat and give it a try.  I'd use a mirror from the port locker and see if it lines up.  Worst case would be to take the port plywood/teak wall off in the aft cabin.  Good luck.

[2ndwish]

On our '87 the fuel tank is most easily accessed by removing the wood panel on the port side in the aft cabin, as Stu said. You cannot completely rule out a wiring problem without accessing the connection to the sender. Getting the panel back on after the repair can be a challenge. We purchased our replacement sender, a Moeller unit from WM, which subsequently failed within a few months. WM replaced it and it worked for about another year until it failed. I'm currently looking for another brand of sender!

Another interesting note on this topic.. A neighbor's C34 also had no read on the fuel gauge, so we diagnosed the problem according to the guide from Seaward on the Tech Wiki page. Gauge passed the test procedure as did the wiring. Getting ready to replace sender, we checked the sender resistance (not part of the procedure) and the sender was fine. We concluded that the gauge was bad even though it passed the specified tests. We verified this by disconnecting the sender wire and putting a resistor from s to gnd on the gauge. We quickly found that the gauge read ~1/2 with 2000 ohms resistance- well outside specified 33-240 ohm range. I had never heard of this particular failure mechanism, but I thought I'd share the knowledge. In short, the test procedure should include a resistance test of the sender after the last step in the gauge test: After disconnecting the sender wire from the gauge,  use a multimeter to measure the resistance between the sender wire and ground (on the gauge) if it reads between 33 and 240 ohms, the sender and wiring are good- the problem must be the gauge (assuming it passed the first gauge test). 

[Craig Illman]

Make sure your engine panel has a good ground. If it doesn't, power may try and find ground through your fuel sender and burn it out. We had one sender fail, then the replacement failed shortly afterwards. After adding a new ground to the panel we didn't have further issues. Might have been a coincidence.....

[Ron Hill]

gwp : You are trying to add two different articles together!!  

One was on Removing and cleaning the fuel tank and the another was on Changing out the fuel sender (with the tank installed)!! 
Yes, you can by removing the post side aft cabin panel, removing the sender to tank screws and lifting it up after removing the Beckson port in the floor of the portside lazerette!!

[2ndwish]

Craig- I can't see how not having a panel ground would kill the sender. The sender is already connected to 12V through the gauge. The coil resistance of the gauge will limit the current which can go through that path no matter what. That said.. it is certainly possible to kill the sender by connecting 12 V directly across the sender terminals (12v*12V/33 ohms= 4.4 Watts!). A bad gauge can therefore cause premature failure of the sender if the coil insulation breaks down and the resistance is reduced. A loose 12V wire touching the sender terminal will have the same very bad effect.

I still can't help but marvel at the design of a fuel tank sender which actually runs current (up to a 0.36 amps in a fault condition) through a potentiometer which is sitting in or next to a flammable fluid. If you look at the sender design, the soldered electrical connections are not sealed and I doubt the potentiometer is either. Whole thing just sits in diesel. Something to be said for counting hours and multiplying by 0.4 gallons. 

[sailaway]

If You short out the sending unit it will read a full tank.  I use a little jumper wire with clips from Radio Shack . Charlie

[Jeff Tancock]

Hey GWP.....
Your boat number is close to mine. I've replaced mine a couple of times. Easy job. Pick up a sender at your local marine store, pull off the wood panels in the aft cabin and you will see it right in front of your face on top of the tank (if your are facing starboard). Three nuts I think, a couple of wires and it's out. Reverse procedure and it's done.
No need to remove the tank.
Keep the receipt so when it fails before the warranty is out you get a new one for free. I didn't but should have!