Fuel guage sending unit

[Jim "SV Ohana"]

I know this has been beat todeath, but I'mabout to install a new sending unit.  Is there any reason I can't test the new one by hooking up the power wire and ground (both test good) before I pull the old one??
thanks
Jim

[captran]

I'd sure be interested in the exact detailed "testing for dummies" description of the process.  When we bought Voyager the dealer replaced the sending unit.  A month later something stopped working and I assumed it was the sending unit so ordered another.  Installed the new one with some difficulty and wouldn't you know it but still the guage still read nada.  Got a new guage and it worked!  It would have saved me some expense and alot of work had I known how to test the sending unit that was already installed.  I know there's something about resistance, but I didn't know how to test which leads.

I have Nigel Caulders Deisel book and the big boat systems book he wrote but I couldn't find anything.  I'd love to get a "Boat Maintainence for Dummies" type book.  I've learned alot, but I've alot to learn.

[Ray & Sandy Erps]

I'm strictly a backyard mechanic, the perfect audience for the Dummy Maintenance Books.  I've burned a fair amount of fuses, learning a lesson each time.  The electrical sending units are usually a on/off switch to ground, or a variable resistance switch to ground.  Either way, the wire that goes to the sending unit usually comes from the guage.  (I'm using lots of qualifiers here)  Take the wire off the sending unit and touch it to ground and watch the reaction of the guage.  That's a quick test of the guage and the wiring all the way back to the battery if the guage reacts to that "backyard" test.  On ohm meter or continuity tester to the terminal on the sending unit should change from when the sending unit is in its resting position, such as no oil pressure or cold engine to when the sending unit is in the activated position, with oil pressure or a warm engine.  That's the simplified version and I'm sure there are lots of exceptions but I'm burning less and less fuses and it works for me.

[Stu Jackson]

NO NEED FOR DUMMIES BOOK

C'mon, folks.

Who needs another book when we have this website.

Sure, it's big, but so's the book.

Read, search, find.

It's all here.

Stu

[Jim "SV Ohana"]

Short version of the testing process that led me to order a new sending unit (got the process from this site)
first ohm the ground wire from sending unit to engine, second remove guage pannel and ohm sending unit wire to guage, third jump from sending unit wire to ground on guage with power(guage should run to full).  Also jumped sending wire to ground on sending unit and guage also ran to full.  Also checked ground wires on pannel.  With all these tests determined a shot sending unit and HOPEFULLY everything else is OK.  Am doing the replacement today, will post results.
Jim

[Jim "SV Ohana"]

Installed the new sending unit yesterday, works like a new one.
Jim

[Stu Jackson]

Jim

Glad to hear it worked.

Did your suggested checks do the trick based on your earlier post?  Is that the right way to PREtest them?

Stu

[Jim "SV Ohana"]

Stu
The post by Bandg lead me to Ken of "family affair" #876 on the faqs page.
I used the tests outlined by Ken which seamed to issolate the problem.  Lots is info about this, but the tests posted by Ken sounded good, I used them and fixed the problem.
All the info is out there.  One of the beauties of owning a Catalina, someone has probably been there/done that.
Thanks again
Jim