I need all the help I can get with this one. I have been reading other Threads related to no AC and Tachometer, but have not been able to find one for a 1996 E320. Does anyone knows if both the AC and Tachometer are related? I also read that the Crank Speed Sensor may be the problem? Any sugestions? I welcome any advice.

Also my Cruise Control stoped working at the same time of the AC and Tachometer. All fuses are good.

I appreciate the help.

my understanding is that if the relay that controls the AC is bad (labeled the "Klima" relay in some models, which is German for climate), it can cause the tachometer to stop working. Why? I have no idea, but I read that in some posts while doing searches on another issue.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car

Thanks for the info. But I understand that the 1996 E320 does not have a relay and is only controled by Climate module or on and off swicth. Perhaps someone can confirm the info.

Thanks

I have read that the tach "tells" the compressor that there are "revolutions" from the engine. If the tach fails, the compressor thinks the car has been turned off and therefore will not engage. A safety feature so you don't burn out compressor. I don't have this on my vehicle, but have read posts that indicate this scenario. Hope this helps a little.

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Nello Tare

1982 300D (266,001 mi.) looking and running great

Previously owned:
1976 450 SLC
1983 300D
1976 300D
also
1982 Jaguar XJ6 (loved, but gone)

He is right, You have a system in your car that compares the speed of the engine to the speed of the AC compressor. If they are off by a certain percentage (I think 20%) the system than assumes that your compressor is jammed and immediately turns it off. The most likely cause of your problem is the engine speed sensor, or its related wiring. This sensor is also the one that feeds your tachometer its signal.

By the way, are you sure that you don't have a KILMA relay? Its typically located in-front of the firewall behind the Battery. Its usually the Relay that does the speed comparison and turns the AC compressor off if necessary.

You can perform a small experiment (will need two people). Turn the AC off and start the car. Look at the AC compressor while someone activates the AC system from inside the car. I bet that you will notice that it engages for a split second and than shuts off. It will repeat this action once you stop the engine and start it again. It will not come on again unless you turn the engine off.

If the above does happen, than my diagnosis is most likely correct.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Thanks a lot guys, I will defenetly will perform the two person procedure/test. On the 1996 E320 the battery is under the back seat and I have looked under every compartment, dash, engine and the only relays that I have found are inside the module compartment on the right rear of the engine compartment. I believe the relay module is called a K40 which has 6 relays inside. I also just finish checking the Crank Speed Sensor (I check it by disconecting it and the car would not start, once I reconected the cable the car started ).

I welcome any more Ideas.

Once again thanks in advance for your help,


Norman