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While driving around today the oil pressure light on the oil pressure gauge in the dash came on momentarily a few times. When I first start the car the presure is at 3 whether I am accelerating or at idle. Once the engine warms up I notice the gauge goes all the way down to zero at idle but rises immeadiately as soon as I accelerate. I believe the light would come on while coasting at idle. When I saw the light come on I would step on the accelerator and the needle would rise and the light goes off. I checked the oil level and it is fine. I will call a service center for an opinion but I thought I would ask all of you first. Thank you.
 

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2003 SL500, 2003 SL55, 2005 S55, (2) 1991 300SLs, 1994 E320 cabriolet
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It's normal for oil pressure to fall as the engine warms-up, and its normal for it to increase with engine speed. A warm engine at idle will typically read about 1.5 bar.

Your oil pressure may actually be very low, Dave. Or you may have a faulty pressure sensor, cluster, or wiring between them.

You can test the wiring and cluster easily yourself. If you unplug the sensor (picture) and connect 150-ohms of resistance to the leads in its place, the pressure gauge on the cluster should read 3 bar (key on, engine off). If it reads significantly lower, wiring or cluster are faulty and further tests are indicated. If it reads okay, you ought to have the oil pressure checked at a shop. They should have an external gauge which they can connect to the engine for this.
 

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