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84 230CE & 84 300DT
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324 Posts
Discussion Starter #1
The tachometer in my '85 300DT doesn't work. Is the tachometer operated by a cable or is it electronic?
I haven't been able to locate the cable (if there is one) yet. Would it be a simple fix?
 

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83 300D Turbo
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Most likely it is the RPM sensor (AKA tach sender unit) mounted on the driver side fende...

Most likely it is the RPM sensor (AKA tach sender unit) mounted on the driver side fender. It is about 1 1/2 inch diameter with attaching cable. It just unscrews. It can be repaired but takes some technical know how. New replacement is $55 from European Automotive Specialists online.
 

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84 230CE & 84 300DT
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Discussion Starter #3
Re: Most likely it is the RPM sensor (AKA tach sender unit) mounted on the driver side fende

Most likely it is the RPM sensor (AKA tach sender unit) mounted on the driver side fender. It is about 1 1/2 inch diameter with attaching cable. It just unscrews. It can be repaired but takes some technical know how. New replacement is $55 from European Automotive Specialists online.
Thanks for the suggestion. This will give me one more thing to check this weekend.
 

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84 230CE & 84 300DT
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Discussion Starter #4
I looked for the item that guavaman mentioned and there didn't look like anything that cou...

I looked for the item that guavaman mentioned and there didn't look like anything that could be related to the tachometer. Anything that remotely resembled what was mentioned had vacuum lines attached. Did I mention that my car was a diesel?
 

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90 300 SE ,85 300 GD
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Tach Amplifier

This is not mechanical, but electronic on your car. The unit should be found on the left front (drivers side) fenderwell under the hood. A gray electrical line connects to the base. This has a strap made of plastic to hold the screw-on cap from falling off onto the ground when you loosen it. Two phillips head srews hold the base onto the bracket attached to the fenderwell. Remove the two screws, then unscrew the cap. A new amplifier is $75-$90 depending on where you buy it. You can install it yourself, no problem. It has pins in the cap that plug into the base. It CANNOT be installed the wrong way![:D]
 

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84 230CE & 84 300DT
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324 Posts
Discussion Starter #6
Thanks for pointing out the tachometer amplifier. I know exactly which one you are talking...

Thanks for pointing out the tachometer amplifier. I know exactly which one you are talking about. The cd manual doesn't show anything related to the tachometer other than removing and replacing it.
 

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90 300 SE ,85 300 GD
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Part number 001 545 59 32

The part number is: 001 545 59 32 and described as "IMPULSE SENDER". Glad you identified it!
 

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84 230CE & 84 300DT
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324 Posts
Discussion Starter #8
Re:

I'm afraid that the part you mentioned doesn't apply to my car. There was nothing but the diagnostic connector there. I have a California model and the EGR control unit is involved with the tachometer. I will have to check all the componets related EGR control unit to find the problem. It may just be that the tachometer itself is kaput.
 
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