4 gallons is about what I remember. Unless your floater gauge is stuck or sticky.

 

After sorting out the ground, it lights up just as the needle descends below the last stripe.

65 liters from filling to auto-stop.

 

x2 - Mine does the same thing... the light comes on at start-up, but I've never had it come on when I am driving, and I know I've gotten very close to empty before.

I've removed and cleaned the sending unit, and could make the light turn on when sliding the float manually up and down the track... hard to believe the gauge has to go down below the line before the reserve light comes on, though!

 

fuel tank is 18.5 gals, with a 2.5 gal reserve-so 21 gals, light comes on at 2.5-3 gals,

mine used to come on right at the 'R' hash or just to the other side, now I don't trust the left half of the gauge(just needs a good cleaning)

 

thanks, I'll be more comfortable to push it a little further next time knowing I had 4-5 gallons of fuel remaining. I need to run it down really low anyway so I can drain the tank and clean the fuel screen. It's got to be due for that.

I don't really need the reserve light. I never run any fuel tank that low unless there are VERY unusual circumstances, but I just want to know if my repair worked. I guess I could lift the sending unit up out of the tank with it plugged in. That ought to make it fall to the bottom and ground out.

 

I believe that the reserve light comes on at engine start for a bulb check, like all the other warning lights do. If you don't get a reserve light at that point the bulb or it's wiring is bad.

The fuel level sensor float actually has contact pins on the bottom of it that complete the low fuel circuit when the fuel level is low enough. When I had trouble with mine it was because there was a pile of muck at the bottom of the gauge tube and the float could not get low enough for the pins to make contact.

 

Yes. The reserve light is part of the "bulb check," and it works as it should when the key is switched.

I recently removed my sending unit and cleaned it of all the tank funk. At that time, I discovered that there was a broken lead that needed to be repaired. This lead is the reserve lead. I soldered it back and was just curious if it was working.

I'll run it a little deeper next time just to see.

 

Agreed. My '82 doesn't check that either. The only way is to tempt fate (if you believe in that shit) and drive until it lights up, or you car dies.

 

i know that on my 240d the Total capicity is 17.5 gallons including a reserve of 2.5 gal. I've brought my down to reserve and it does indicate correct after filling it up.

 

Low fuel

1983 low fuel light comes on at start up, but has stopped coming on when tank is low. May need to pull the sending unit. Where do I Access it? 300dt sedan is the model

 

My light is on all the time even after fill ups.

 

Then you probably need to clean out the sender - but first check for a secure connection on the sender as they are often pretty loose

 

Make sure you have a *good* earth ground... Just posted this elsewhere...

My experience with the 300s cluster gauges/lamps is that there is an earth ground in the cluster and what I have done to fix *most* cluster related problems is to pull the cluster... attach a stranded wire to the center (speedometer) housing (I put it at the top on the left side for ease of access) ... then, run the wire straight back and there is a very accessible screw on the firewall (on the 300s) to ground it to. Leave a little slack for ease of installation and removal.

This has fixed many a problem for me and it's very cheap and easy.