Really Basic Question: Fuel Tank Sending Units

[CptStickfigure]

I was browsing that tech site Hankcash posted about (http://www.jalopyjournal.com/ubbthreads/showflat.php?Cat=&Number=497105) and it reminded me of a question I've been meaning to ask.

Are fuel tank sending units more or less interchangable?

The unit on my '51 chevy is broken and I'll be rewiring anyway, so it seems like as good a time as any to replace it. Since I've already done the 12v conversion, it seems kind of goofy to put a 6v unit and voltage reducer back on there if I can use a 12v unit and be done with it.

Any thoughts?

[Petejoe]

no they are not.
Each unit, works differently. The ohms are the key.
Some operate at a lower range of ohms others at a higher range. You can't mix the senders up with the gauges.
Another thing... A 12volt system will fry a 6 volt gauge if there is no step down transformer in there.

[CptStickfigure]

[ QUOTE ]
You can't mix the senders up with the gauges.

[/ QUOTE ]

So, theoretically anyway, I'd need to grab a sender and gauge as a matched set if I was going to try a different sender?

[ QUOTE ]
Another thing... A 12volt system will fry a 6 volt gauge if there is no step down transformer in there.

[/ QUOTE ]

Yup. I knew that part already.
And not even from personal experience.

Thanks.

[Petejoe]

[ QUOTE ]
So, theoretically anyway, I'd need to grab a sender and gauge as a matched set if I was going to try a different sender?

[/ QUOTE ]
Exactly....
Then it it wont matter which ranges you chose as long as they match. Some sets are empty at the higher ranges and full at the lower ohm ranges. Other are opposite.
They are all over the board in ranges too. The trick is to find one that matches your dash gauge ohms if your using a stock gauge. There are alot of aftermarket sending units that can adapt to your tank. Just be sure that the float travels the whole movement range and there's room to do it.