I was wondering if anyone else has had a similar problem and hopefully a solution. My SD runs at about 95-96C (ambient air temp being ~90F) on the highway doing 65-70 mph but all of a sudden the temp gauge will jump up 8-10 degrees(instantaniously) run there for a while and then jump back down to what I consider normal at 95C or so. It acts like there is a short of some type sometimes and it will jump up and down real quick. Also the fuel gauge has the same problem but they dont seem to be syncronous with each other.

I am thinking of replacing the temp sending unit and the thermostat. I am sure that the problem is not the thermostat because of the instantaneous reading change. I gues pulling the instrument cluster and looking for obvious shorts is also a consideration.

Has anyone had a similar problem and fix??

Stephen

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85 300D 305K miles WVO(105K so far), Mine
82 300SD 235K miles BIO-D, Wifes
96 F250 SC PSD 4X4 285K MILES BIO-D, Ours
89 BRONCO 182K MILES sold
Finally Compression Ignition Only!

yeah also had the same problem here.

checked and cleaned the connection at the temp sender on the block. also found another corroded connection which not sure if related or not but cleaned it anyway. problem went away sofar without replacing anything.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

Check the ground connections behind the instrument panel. There are 2 clusters of brown wires connected to 2 ground points on the steering shaft. If you pop the instrument cluster forward and push the speedo cable from inside the engine compartment you should have enough room to see and get a long extension for the socket.

Mine were loose on the 240D. The gauges were jumpy and they also flickered when I used the turn signals. Once the ground clusters were tightened, solid as a rock.

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79 240D (no name yet) 203K Miles Maple Yellow
98 2500 4x4 HD Dodge 24 Valve Cummins TD
83 Chevy Van (Dead-Trans. shot)

I have an extra instrument cluster, so I swapped that whole left side unit and the problem went immediately away. The other one would give the correct temperature most of the time, but still when it jumps up your mind has to start to wonder if this is a true overheat. Mine was not an electrical connection on back, as I had scotch-brited all pins and had it in and out a good 10 times for speedo cable, odo. repair, lights, etc...
JL

I hate not knowing for sure even though 100C is not really overheating. I would like to know it is running at 95C or so all the time like it reads occasionally.

Thanks for the ideas I will research them ASAP and respond.

Stephen

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85 300D 305K miles WVO(105K so far), Mine
82 300SD 235K miles BIO-D, Wifes
96 F250 SC PSD 4X4 285K MILES BIO-D, Ours
89 BRONCO 182K MILES sold
Finally Compression Ignition Only!

check the brown wires behind the gage cluster I drove myself crazy trying to fix the same problem and eventually took the car to a car electric specialty shop they cleaned the ground wires behind the cage cluster where they ground to sheet metal
and the car works perfectly now I am almost $200.00 lighter though

don't ya just love the german wiring? well this is my 2nd german made rig, and see alot of the same problems in both. like the others said, check those grounds, and all those connections also till problem goes bye-bye. in my case, the tac's worked when they wanted to... hehehe... so I took the sensor out slightly bent the pins and reinstalled, tac works fine now, same with the goofy headlite connector, no high-beam, bent pins slightly now it works right. having a spray can of contact cleaner is nice to have handy also.

Pindelski ran a short repair story here once and I think he removed the temp guage and dropped some oil in on the center shaft. Said he used a jewelers tool to squirt the graphite in there.
I have that same proplem, cleaning the electrical connections fixed most of the problem, but it still jumps around sometimes.
Thinking to tear it apart sometime and maybe use a syringe with a good quality graghite lube and see what happens. Fixed my wifes anniversery clock using that.