Do aftermarket fuel gauges work with the M-B sending unit?
 

Do aftermarket fuel gauges work with the M-B sending unit? Just wondering if they're compatible "electrically". Units like this:

JCWhitney item# ZX528930X

I know this is a longshot, but what about with a Smiths gauge from the 1970s - from a British car, probably an MG or Triumph?

Just wondering if the sending unit from a W123 would work with non-MBZ gauges...

Thanks,
Scott in Penfield NY
1982 300D Turbo (with a rusted out right rear semi-trailing arm)

I can only speak from experience from doing a fuel gauge swap from the stock VW to an AutoMeter guage.

The determining factor here is what resistance range does the gauge recognize? You also have to know what the ohms the sender puts out at the full and empty levels in the tank.

When I got the Auto Meter gauge, the kit included different resistor packs to match senders from Ford GM or Chrysler vehicles. Turned out the Chrysler pack more closely matched the original VDO sending units.

I'm not sure when British cars universally went from positive to negative ground, but it may be a concern when it comes to illuminiating a Smith fuel gauge...the sender connection would still fall under the same constraints as far as resistance range.

For MB, I believe VDO gauges would more closely match MB resistance specs.

The Smiths guage is negative ground, but I've no idea how to find the specs on it, I've heard that older cars usually use 0-30 ohms...

VDO guages are sold in models with these various specs:
0-90 Ohms
10-180 Ohms
240-33 Ohms
73-10 Ohms
10-80 Ohms
90-0 Ohms Tube Type Sender

The 300D manual says the sender goes from 1.6 (+/- 0.7) ohms on Full, to 56.9 (+/- 1.9) ohms on Empty. So, does that make the sender a 60-0? 0-60?

Maybe if I look at the VDO website I can determine if "0-90" is for empty-full or full-empty...

OK, I found a VDO gauge, model 301-107, that works with a "90-0 Ohms Tube Type Sender", and the instruction document for that gauge says it's adjustable from 60-90 ohms. That sounds like it's the one. Around $25, as far as I can tell.

Sounds like the way to go!