Testing 330GT 2+2 Fuel Sender Unit

Hi Darren, the Ferrari sending unit is nothing more than a variable resistor (a rheostat). You’ll need to mount the sending unit onto something solid, as if it is bolted onto its normal working position, then put a 12V battery, the sending unit and a voltmeter all in series. Now, you move the “arm” of the sending unit from one stop to the other and you should see the voltage reading dropping gradually from 12 volts to near zero. What’s important here is that you witness a steadily increasing (or decreasing) voltage as you move the arm.

john

 

Hi Darren, the value of ohms isn’t important. The coil is either wholesome or it’s compromised. Take the back cover off and if the coil, as well as the sweep, look clean and tidy the gauge should work. But, I can take a full range resistance reading tonight and report. Here’s how it should look inside.

john
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Hi Darren, sorry it took awhile to get back to you on this. As you can see in the photo, there are two terminals on the sending unit. The resistance between one of the terminals marked "T" and the chassis of the unit at "full-tank" is about 100 ohms. Now, if you jack up the arm all the way to the "stop", the reading will suddenly jump from 100 to 200-something, but that's a wild reading that has nothing to do with the function range of the unit anyway. The operating range of the gauge is about 10-100 ohms.

BTW, the second terminal marked "W" is merely a feed to the warning/empty light within the gauge. Hope this helps.

john