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  #1  
Old 10-08-2003, 08:02 PM
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tach signal

I have a MB 230 ce '87 w124.

I am trying to find some sort of positive increasing tach-signal to use for a remote start kit.

The standard tach-siganl in the dash decreases by decreasing rpm.

I've tried to measure the wires at the coil, but they seem rock steady by rpm.

And, I guess, the sensor output at the test connector won't give me more than a few mV? I need at least a couple of volts in idle.
Pulses of 12V are OK, as long as they increase with rpm.

Any ideas? Are there a signal available at the distributor?

Thanks in advance!
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  #2  
Old 10-08-2003, 09:01 PM
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If you have a Klima relay for the AC I'm pretty sure it'll have an rpm signal of some sort.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD
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  #3  
Old 10-08-2003, 09:11 PM
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Yes, I have an A/C, but is this the relay located behind the battery?

And, by the way, what is the A/C using the tach signal for?
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  #4  
Old 10-08-2003, 11:10 PM
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smoke gets in your eyes
 
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If there are wires sticking out the back of the AC compressor, the compressor has a rpm counter. The Klima relay compares the compressor to engine rpm to decide if the compressor is working properly. If the compressor is dragging or seized, the Klima relay cuts power to the compressor clutch to save the serpentine belt so as not to strand you. I don't know if nonUS cars have this feature.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD
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  #5  
Old 10-09-2003, 12:06 AM
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Yes, I've checked with a local A/C repairsman.
He confirms that the compressor relay has a safety-feature which compares the RPM :-)

Now, if someone could tell me where to locate the relay I'd be a happy man!

PS: Do you know for sure that this signal i adequate to my use (as described above), or is it just a try-and-check suggestion?

Anyway, thanks for the tip!
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  #6  
Old 10-09-2003, 01:32 AM
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smoke gets in your eyes
 
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This thread might give you some ideas - 86SDL A/C Question

As to where the Klima relay is in your car, I have no idea. But I imagine it's in the same place in any W124.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD
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