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Old 05-04-2009, 02:29 AM
Join Date: Dec 2008
Location: California
Posts: 111
Question temp gauge, what's the trick to repair?

92 300SD temperature gauge goes up an down, some times is steady and some times jumps. It will go steady after I put presure on the back of gauge with my finger. My question is, is there something to replace the gauge?. Can we exchange parts of it with out changing the whole gauge unit?. Can the miles be reset if I buy a used from recycling yard? Please advise.
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Old 05-04-2009, 03:21 AM
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Change the sender on the engine.
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Old 05-04-2009, 05:28 AM
oldsinner111's Avatar
a parent should die first
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Location: bristol,tn
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Also check the plug, on mine the plug opens.The wire had come losse,and I resolder it.
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Old 05-04-2009, 11:33 PM
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2 doors, 5 cylinders
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As said, i'd resolder as much as possible on or around the gague, sounds like it could be a loose ground too.
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Old 06-26-2011, 10:23 AM
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Whats the easiest way to get to this temperature gauge and where is the sender located?
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Old 06-26-2011, 10:42 AM
oldsinner111's Avatar
a parent should die first
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Like the w123 cars,I also added a ground to my dash.The sender on the side of the head is for the gauge.The one near thermostat is for the glowplug unit.As I said before the plug on these senders open up.Some times the wire breaks I had to solder mine.
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Old 06-26-2011, 11:24 AM
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Originally Posted by jmbeam View Post
Whats the easiest way to get to this temperature gauge and where is the sender located?
Pull the cluster and take it apart. The three gauges (fuel, oil pressure, coolant temp) are a unit and that is the only way to replace it. You do not have to replace the whole cluster so don't worry about resetting miles. The cluster is in 3 parts -- gauges, speedo, clock/tach. They are separately replaceable. Speedo and clock/tach may vary from model to model, the gauges are all the same except that gassers get a vacuum "Economy" gauge and later ones say "Must use unleaded gas." My '87 300D in fact has a cluster from a gasser, it works just like the diesel ones.

It is theoretically possible to take a gauge apart but I don't recommend it. As the others have speculated, you probably have a bad connection somewhere in the cluster.

The sender is located in the water jacket, on the left side of the block at about the midpoint. You have an OM602 engine and I am not quite as familiar with it as I am the 603. If you can put your finger on the gauge and it stops jumping then it is probably not the sender.


"Buster" in the '95

Our all-biodiesel family
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Old 06-26-2011, 01:51 PM
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Location: Redding, California
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Sounds to me like an electrical short somewhere between the sender and the gauge. Could be a crystallized or corroded joint in the wiring.

As for taking the gauge itself apart, it's quite simple. You have the windings which plug into the circuit board. If you pull the needles off all the gauges and remove the faceplate, the winding for the gauge comes right off the pins. You might clean off the corrosion and resolder the circuit board, which also is known to crystallize the solder joints leading to poor connections.

This is the bare circuit board with gauges removed. In the center/left you see two connectors for the windings of the fuel gauge. Above center are the two for the fuel gauge and to the right, the oil. Picture taken just before resoldering all the connections.

If you choose to pull it apart, repaint your needles while you have them off, much easier that way.

Last edited by Bob338; 06-26-2011 at 04:39 PM.
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