Ok, probably been asked before, but a forum search turned up nothing for me so here goes. Has anyone ever found a way to successfully hook up an idiot light as a low oil pressure indicator on a W123 300D? I know the 300SD has an electric gauge, but the 300D is a mechanical one. I would like to install a light to warn me if oil pressure suddenly drops. I know the gauge is sufficient, but at times my attention is focused on driving and traffic and I don't notice the gauge as often as I should, where a bright red light (flashing or not) would catch my eye, and possibly save an engine.

If anyone has done this or can give me a link to a good how-to, I would appreciate it.

Thanks!

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

Anyone??

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

get something like the oil light kit on amazon

and plumb into the oil system

https://www.ebay.com/itm/270741238800?epid=655428043&hash=item3f096f7410:g:NukAAOSw0h9ZttVA

Sorry, but I can't shed any light on this subject. I've often wondered about this, myself. In addition to the "idiot light", I would think an audible alarm would be a great addition, as well. Something along the lines of that nasty OEM "buzzer" that so many find offensive (that would be the perfect warning for low oil pressure). Unless you're driving at night, the few warning lights this car does have, are hard to notice in daylight ("Brake" light comes to mind).
My guess is MB had no idea, not in their wildest dreams, that so many people would be driving so many of these cars (daily), 40-50 years after production, that low oil pressure would ever even be an issue.

If you didn't mind the modification, the electronic oil pressure gauge from the w126 617 can thread into the same port as the oil pressure line from the w123 617. You might be able to retrofit the needle from the w126 into a w123 cluster.

Not a great solution, but it might help.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

I'd think one could measure the resistance of all main positions of the OE oil pressure gauge, then splice into its wiring with a relay that would close and turn on the buzzer if certain resistance range is achieved. Unless that gauge works by measuring current, then it's a bit different.

Edit: look here https://www.electronics-tutorials.ws/opamp/opamp_5.html

section "Light Activated Differential Amplifier"
you'd need your existing wires instead of LDR in that circuit and then fine tune to find the threshold you want

Edit2: Even simpler, perhaps you could use a MOSFET to drive the buzzer/light; https://www.electronics-tutorials.ws/transistor/tran_6.html

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*** I can unlock your Becker 754/780/1492, add aux/bluetooth...

I was just thinking about this a few weeks ago myself. Seems like a worthy modification, since one could save their engine in certain situations.

Cheap low oil pressure alarm.
Low oil pressure alarm for 617.952

There is also I think 2 other threads on the subject.

One of the things that one of the members said stuck out. When you are on the Freeway and your oil pressure is above 3 bar and say a oil cooler hose pulled out it was speculated that by the time the oil pressure dropped to say 7 psi (0.5 bar) there would likely be damage to the engine. Of course there is a chance of lessening the damage with the alarm instead of driving not knowing about your loss of oil pressure till the Engine stops.

What is needed is something that kind of goes off of the throttle lever angularity as compared to the Oil Pressure.
Or some sort of pressure differential setup with one side hooked to the most likely pace for an oil pressure drop.

Some of the newer then my 1984 models have some sort of low oil level in the oil pan gauge or alarm. Since I don't have a newer model I did not pay attention to the details.

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84 300D, 82 Volvo 244Gl Diesel

All 1986 and newer benzes have a low oil level light. 190e/d had it from 84.

Its just a yellow light without audible alarm

They also have a low coolant light and a bulb out warning(except 190)

I think if you're gonna bother, low pressure is too late and of course you get false alarm when starting. Low level is more useful because that's gonna precede low pressure by a few quarts of loss. I scrapped a 602 motor a while back and it had a float switch in the lower pan for a low level alert. You could probably weld, braze, or JB Weld a bung into a 61x lower pan to use a 61x oil level switch for this purpose.

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CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

Considering sensing pressure loss versus volume loss, I'm likewise more inclined to the latter. I've looked at pictures of some of the M-B sensors, "float switch", but I do wonder:
Wouldn't it be rather challenging to figure out the optimal or near optimal level on the pan to mount it? Maybe I'm overthinking it or missing something obvious...

On the oil level little buzzer could be taped into that I think.

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84 300D, 82 Volvo 244Gl Diesel

I'm looking at this strictly from the angle of the oil cooler lines goin tango uniform. Should this failure occur, does it really matter if you're being made aware of "low pressure" or "low quantity"? In this catastrophic scenario, I tend to believe the driver needs to be alerted to SOMETHING and damn fast. Visual, audible, pressure, quantity, does it really matter? Just something else besides that tiny needle on the oil pressure gauge, silently dropping to zero, is what I'm talking about. Personally, I'd have about a snowballs chance in h-e-double hockey sticks noticing that before it's too late. FWIW, if oil cooler lines went south, I'd think you'd see pressure loss before all the oil was on the ground. I don't have proof....just a guess.

I have a feeling the Oil pressure is a lot higher then you think. My Oil Pressure maxes out at 97 psi (that is 7 plus bar. Notice your gauge only goes up to 3 bar). Also the Oil Pump on the OM617.952 is huge. What the means is if there is a leak a lot of Oil is gone quickly.

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84 300D, 82 Volvo 244Gl Diesel

I'm not an expert on the subject so I'm unable to say one way or the other definitively.

On the other hand, there is no rule I know of that says one cannot set sensors for *both* pressure and quantity (though as I wrote above, I'm not sure that I could get a volume measure sensor arranged properly). Overkill? Maybe, but that is a personal choice.