fuel sender testing

[JoeGrapes]

Ok, I've read all the posts about fuel sender testing. According to the factory specs the sending unit should read about 10 ohms full and about 73 ohms empty. I just got a new sending unit from E-Bay. I set my multi meter to the 200 ohm scale and it reads .6 full and 4.7 empty. If I set the scale to 2000 it reads 2 full and 16 empty. When I hook the unit to the car the gauge in the dash reads full when the sender is full but it reads empty when the sender is at about half.  Now my overhead warning light is always on. I have two relays and they both do the same. I took the relays apart and found nothing bad and continuity is good every where. I don't really no any way to check the relay other than look for obvious burning and checking continuity. I even cleaned the little points in the relay and checked to be sure they were working. Shouldn't all Mopar sending units read the 10 ohms and 73 ohms in order for the dash gauge to read correctly? 

[soundcontrol]

Is your ohm meter analog or digital? Analog meters can be very rough. Check with a digital meter if you have an analog. Should be 10-73, maybe you got a bad unit...Also check your ground at the tank, mine was very funky when the ground connection was bad.

[JoeGrapes]

I have a digital meter. I tested the unit on the bench and got those readings. Then I set the unit on the floor under the tank and connected it with alligator clip leads and got to see how the gauge read. My gauge needle moves kinda rough at the beginning. My original gauge crapped out so I'm using the guts out of an A body fuel gauge. Could they be different? I should just bit the bullet and buy a new gauge on E-Bay for $79. But that still doesn't explain the different ohm readings I'm getting from the new sending unit.   

[shawge]

Is the sender well grounded?

[JoeGrapes]

yes it is. I contacted the company I bought it from and they want me to call the in the morning. I'll see what they have to say.

[dodj]

You need a replacement unit. The one you have is faulty.

[JoeGrapes]

I talked to the guy this morning and he took out another one and tested it while I was on the phone. He got the correct readings so he's sending me a new one. See if this one works.

[JoeGrapes]

OMG! My multimeter is not reading correctly. I checked 3 different sending units and all measured .7 to 4.7. I thought this can't be so I borrowed a multimeter from a friend and it read just what the sending unit is suppose to read. My multimeter reads volts fine but screws up on ohms. How can this be I asked? I even changed the battery with no effect. 

[dodj]

OMG! My multimeter is not reading correctly. I checked 3 different sending units and all measured .7 to 4.7. I thought this can't be so I borrowed a multimeter from a friend and it read just what the sending unit is suppose to read. My multimeter reads volts fine but screws up on ohms. How can this be I asked? I even changed the battery with no effect.

The voltmeter uses a different circuit in the meter than the ohm meter. One possible reason is that you tried to read volts when the leads were plugged into the ohms spot. If the ohm meter is not fuse protected,  that would screw up the meter. But volts  still work