Bad Fuel Sender I think. Here are my ohm readings

[reelop19]

OK I have an 89' 325is so it has 2 fuel senders. I'm pretty sure my tank is close to empty also.
Passenger Side Sender: .4 Ohms
Drivers Side Sender: 75.4 Ohms

I was thinking full should be around 0 ohms but I also thought empty was less than 75.4 ohms. Can anybody clarify this for me? Maybe give me some insight as to what sender I need to get? Thanks

[IronmanE30]

This may help.

http://www.r3vlimited.com/board/showthread.php?t=159981&highlight=fuel+sender+ohms

Cheers,

Jim

[reelop19]

I don't think that helped a bit. I have 2 senders that are reading opposite of each other leading me to believe its the senders. My gauge always says "E" and my OBC always says 30 miles left in the tank. I believe its my senders just which one because I need to know the precise readings I should be getting. For all I know they could both be bad.

[jlevie]

All of the senders that I've checked read zero for full and 58-62 ohms for empty. It appears that the passenger sensor. You'll need to pull the other sensor and see if it will go to zero when upside down.

[Jean]

http://www.r3vlimited.com/board/showthread.php?t=86834

You should see the following
74 Ohms -> empty
35 Ohms -> at 1/4 + 1/16 tank
24 Ohms -> at 1/2 tank
16 Ohms -> at 1/2 + 1/8 tank
11 Ohms -> 3/4 tank
5 Ohms -> full

Pretty much how mine measured as well.

[Jean]

89 e30 ETM shows that both senders are connected in Series. The left tank fuel sender goes to the fuel gauge via pin 4 (br/gn) wire and also goes to the on board computer (br/gn), the other end of the left tank fuel sender is connected via br/gn to the 2nd fuel tank sender that has a switch on it (switch closes when tank contains less than 1.5 gallons) to trigger the low fuel light in the cluster. BR wire is ground, and the br/gy is the 2nd wire going from the second sender back to the cluster (and obc via br/gy). the on board computer basically reads from the two senders, so if your fuel gauge and on-board computer aren't reading correctly you need to test both senders.

looking at the schematics both senders should read close to 0 when full. it's like a variable resistor with the "wiper or the middle arm" going up/down as a float.

pull the driver's side sender out and test it, you can flip it upside down and see if it sticks and/or changes resistance gradually....

[reelop19]

I'm trying to get this thing out but the tabs are in the way. How do you get the senders out?

[Jean]

The one on the driver's side you twist and pull, passenger side is just 4 nuts.

[reelop19]

Yeah I got the passenger side but the drivers side won't come out. I tested the passenger side when it was out but theres 3 prongs whereas the drivers sdie had just thos 2. IDK any tips

[Jean]

Yeah I got the passenger side but the drivers side won't come out. I tested the passenger side when it was out but theres 3 prongs whereas the drivers sdie had just thos 2. IDK any tips

Yes, it's got 3 because it's got a switch to turn the light on/off.

Download the ETM, it will make sense.

2nd fuel tank sender that has a switch on it (switch closes when tank contains less than 1.5 gallons) to trigger the low fuel light in the cluster.

[reelop19]

Well theres a dent in the bottom of my tank on the drivers side which could be why my drivers side sender won't come out. I think I'll just replace the passenger side one first because its obviously bad based on the readings.

[Jean]

Well theres a dent in the bottom of my tank on the drivers side which could be why my drivers side sender won't come out. I think I'll just replace the passenger side one first because its obviously bad based on the readings.

I'm pretty sure my tank is close to empty also.
Passenger Side Sender: .4 Ohms
Drivers Side Sender: 75.4 Ohms