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1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #1
Ever since I've had the car, it has a wonky gas gauge needle. I will have a half a tank or more it will point to R, even if I am not moving. Sometimes it will stay on R, and shoot back up to what my gas really is after awhile. What could that be about? The battery is on tight, so it's not that. :confused:
 

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99-C43, 05-G55K, 71-280SL, 94-E320 CAB
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Ever since I've had the car, it has a wonky gas gauge needle. I will have a half a tank or more it will point to R, even if I am not moving. Sometimes it will stay on R, and shoot back up to what my gas really is after awhile. What could that be about? The battery is on tight, so it's not that. :confused:
It's probably the sensor/sender.

But before you replace it run a bottle of Chevron Techron through your tank as per the instructions.
The Sensor/sender may have a sulphur buildup on it which will give erratic readings and the Techron should clear this up.

You may have to do a few tankfuls of gas with the Techron...it will also help to clean your fuel delivery system along with the injectors.

Ed A.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,696 Posts
In addition to what has been suggested, you might try cleaning the grounding point for the sender. It is in a large mass of wires next to the antenna, held in place by one bolt. Just pull all that down and clean the surfaces. Brown is ground

Good Luck,

Jayare
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
In case you didn't know it, the fuel tank in your car is located crosswise at the front of the trunk. You can remove the fuel level sender from the trunk compartment after unhooking the trim panel that hides it from view. The sender is part of an aluminum tube about the size of a paper towel tube. You unscrew the big aluminum nut under the connector and then simply withdraw the sender from the tank. You can do this with fuel in the tank, almost a full tank in fact. Smoking not recommended during the process.
 

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1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #5
It's probably the sensor/sender.

But before you replace it run a bottle of Chevron Techron through your tank as per the instructions.
The Sensor/sender may have a sulphur buildup on it which will give erratic readings and the Techron should clear this up.

You may have to do a few tankfuls of gas with the Techron...it will also help to clean your fuel delivery system along with the injectors.

Ed A.
I had tried one cleaner I bought from Autozone already. Is Techron supposed to be the best in cleaners?
 

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Registered
1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #6
In addition to what has been suggested, you might try cleaning the grounding point for the sender. It is in a large mass of wires next to the antenna, held in place by one bolt. Just pull all that down and clean the surfaces. Brown is ground

Good Luck,

Jayare

Aw, thank you Jayare! Is that under the trunk? What do you suggest I clean it with chemical-wise? Do I clean the connectors or the wires themself?
 

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Registered
1989 Mercedes 300E, 106500 original miles
Joined
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136 Posts
Discussion Starter #7
In case you didn't know it, the fuel tank in your car is located crosswise at the front of the trunk. You can remove the fuel level sender from the trunk compartment after unhooking the trim panel that hides it from view. The sender is part of an aluminum tube about the size of a paper towel tube. You unscrew the big aluminum nut under the connector and then simply withdraw the sender from the tank. You can do this with fuel in the tank, almost a full tank in fact. Smoking not recommended during the process.
After you do that, do you replace it, clean it? Thank you, I hope that will be last resort. I hope the fuel cleaner route will work.
 

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1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #9
Recommended by Mercedes....

Ah, thank you. I don't think I had the Techron one. I will give that a try next time. :thumbsup:
 

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1997 S500, 2005 S500
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171 Posts
In addition to what has been suggested, you might try cleaning the grounding point for the sender. It is in a large mass of wires next to the antenna, held in place by one bolt. Just pull all that down and clean the surfaces. Brown is ground

Good Luck,

Jayare
+1

I had the same issue on my 89 300e...I had replaced a faulty antenna motor and knocked loose those ground wires and the gauge flickering began.

Tightened those back up and it has been rock solid since.


Sam
 

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1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #11
+1

I had the same issue on my 89 300e...I had replaced a faulty antenna motor and knocked loose those ground wires and the gauge flickering began.

Tightened those back up and it has been rock solid since.


Sam
Thank you, are all those wires in the trunk area?
 

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1997 S500, 2005 S500
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Yes all of the wires are in the trunk on the drivers side. Pull back the trunk lining on the drivers side and look next to the power antenna motor.

Here is a pic of the location and wires -
 

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1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #13
Yes all of the wires are in the trunk on the drivers side. Pull back the trunk lining on the drivers side and look next to the power antenna motor.

Here is a pic of the location and wires -
:bowdown::bowdown::bowdown::bowdown::bowdown::bowdown::bowdown::bowdown:


Thaaaaaaaaaank you, that helped heaps!
 

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1989 Mercedes 300E, 106500 original miles
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136 Posts
Discussion Starter #14
Yes all of the wires are in the trunk on the drivers side. Pull back the trunk lining on the drivers side and look next to the power antenna motor.

Here is a pic of the location and wires -
Yay, with the connectors cleaned and tightened, it seemed to do the trick. Thank you guys! :D:D:D:D:D:D:D:D:D:D
 
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