Does anyone know about the reference sensor on a diesel? From what I can guess since it connects at the front of the flywheel and goes to the tachometer amplifier it must feed rpm information to the tach. I have an inoperable tach and I'm sure both the tach and the amplifier are good. I'm getting no voltage from the sensor nor resistance with ohm meter. Is it supposed to have something coming from it? duh?

I also have a functioning new amp and new gauge in the dash but 0 movement from the gauge whatsoever, so I also suspect the sensor....is there a way to test it/get a reading from it to verify its working? I'd suspect it emits some sort of electrical pulse right?

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I haven't really researched this but the sensor is probably a hall effect and has to have power to it to put anything out and it should put out a square wave.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

With three college degrees I'm sorry but that went right over my head...laughing. None of those degreees were in electrical engineering or related fields.

Hall effect is just a switch that is turned on and off by the presence of metal. Like I said I have to get my books out to see and they aren't available to me right now. I was hoping someone that knew for sure would put thier two cents in otherwise I could respond later when I get a chance to see.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

fwiw-

The '82 and '84 sensors are different. '82 picks up from front of engine - gray wire to tackamp on left fender(inside). Amp is black cylinder

'84 picks up at rear of engine - don't recall amp configuration

'83 has smaller amp inside left fnder - don't recall pickup location

( I stil have '82, '83 & '84 no longer around)

Where is the location of the sensor on an '85?

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Hello there. Does anyone know the nature of the speed signal that comes out from the mechanical speedometer on a 1989 MB 300E?

There is a coil that moves the speedometer coming from the transmission to the instrument cluster.
Attached to the speedometer, behind the instrument cluster, there is a Hall sensor that sends an electric signal to the computer and other systems.

Does anyone know if this signal is ratiometric (analog) or digital?

Maybe there is some link out there to learn about all the sensors in the car and where to find the cables that carry the signals, in case one want to take advantage of them (as I am trying to).

There are other speed sensors in the car but I have no reference as where are the cables of these signals. For example, differential signal, wheels speed signals.

Thank you in advance for any help and comments.

OldBeaver

The change came in '84. I understand the later units take a signal from the transmission.

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83 SD

84 CD