Fuel Gauge Fault?

[paulthetester]

I have a 1993 E280 W124 with a fuel gauge with a mind of it's own, sometimes it reads correct and other times it's up and down and the needle moves very fast and not gradually. First I though sender unit in the tank so I measured the restitance out of the unit when the fuel level I thought was about half way between empty and the Quarter mark, It read 80 ohms so I made a resistor out of an old balance knob off a car radio and set it at 80 ohms then unpluged the multiplug at the tank put the resistor on the plug (loom side) and sure enough it read the same as when the plug was on the tank but then the needle went up and down again by itself,
I've checked charging voltage that is stable at 13.7 V at idle so it only really leaves the gauge or a voltage stabliser if there is a seperate one. Anyone any idea's which one it could be or is it all one unit?

Cheers

 

[Hertfordshire Merx]

If my memory serves me right there maybe a voltage stabiliser on the rear of the instrument cluster. I would need to check WIS to clarify this. Would need your baumuster (first 6 digits of your chassis number) to search it properly.

 

[paulthetester]

Hi there thanks for your reply, the first digits of my chassis number are WDB124082

Thanks Again

 

[luders79]

there are screws on the back of the instrument cluster which hold the different clock faces all together on back of pod! They also make a earth contact between each part i think so worth taking pod out and checking they are all tight! i've had a similar probelm before and sure i did the above!

 

[Hertfordshire Merx]

Hi there thanks for your reply, the first digits of my chassis number are WDB124082

Thanks Again

I'll look on WIS foryou tomorrow and post up what I can find. Unless you want to PM me your phone number and I'll talk to you about it. Whatever is easiest.

Regards,

Phillip.

 

[bigasotonuk]

Hi,
I have the exact same symptoms on my 97 C230K, It always follows when I have used cheap supermarket fuel, this is allegedly the lack of detergents in it and you get a build up on the sender unit, thus giving erractic readings if you do a search on here you will find it is very common, though I have never heard of it on a 124. You can run a fuel system cleaner through the system this has the same results as using a better quality fuel.

 

[Hertfordshire Merx]

Have got the instructions of WIS for you to have a look at, there are 4 pages of instructions, any problems give me a call and I'll do what I can to help out.

Phillip.

 

[paulthetester]

Thanks for that I've printed them off and now I have some data to work with, any tips on getting the instrument cluster out. I am a mechanic and in the trade hence paulthetester, Mot tester that is, however I've never taken one out before on one of these and don't want to leave any marks around the cluster.

Thanks