Testing Spd & Ref sensors??
10-30-2009, 09:08 PM
#1
Three Wheelin'
Thread Starter
Testing Spd & Ref sensors??
Probably a dumb question here... 
trying to test the ref. sensors and I'm not getting any readings. I have the meter set at 2k, where should I set the meter at? and I'm assuming ignition needs to be on to have current running through it?
Thanks
trying to test the ref. sensors and I'm not getting any readings. I have the meter set at 2k, where should I set the meter at? and I'm assuming ignition needs to be on to have current running through it?Thanks
10-30-2009, 09:17 PM
#2
To test the sensor you need a scope to determine the voltage while cranking. The spacing of the sensor (0.8mm) determines the voltage. If you just want to see if the sensor coil is not damaged, unplug the sensor and read the resistance. I think it is around 1K ohms. There are three pins, two pins go to the coil (pins 1 and 2) and the other is a shield ground (pin 3).
10-31-2009, 03:09 AM
#5
Sorry but that will generate incorrect readings. The sensor generates a voltage spike when the metal gear/stud passes next to the sensor. You can't measure resistance when voltage is being generated. Why.. the meter generates a constant current and measures the voltage to determine the resistance. (ohm law). The voltage from the sensor will disrupt the voltage reading and generate an incorrect reading.
Last edited by Bri Bro; 10-31-2009 at 05:31 PM.
10-31-2009, 03:14 AM
#6
Three Wheelin'
Thread Starter
So as per clarks, to test for resistance (ING-02) should the ignition be on or off? I tried it both ways with the meter set at 2k ohms and got nothing, no reading. Does this mean the sensor is toast?
http://www.clarks-garage.com/
Speed Sensor
Terminals Resistance Reading
8 - 27 600 - 1600 ohms
8 - 23 > 1 M-ohm
Reference Sensor
Terminals Resistance Reading
25 - 26 600 - 1600 ohms
25 - 78 > 1 M-ohm
http://www.clarks-garage.com/
Speed Sensor
Terminals Resistance Reading
8 - 27 600 - 1600 ohms
8 - 23 > 1 M-ohm
Reference Sensor
Terminals Resistance Reading
25 - 26 600 - 1600 ohms
25 - 78 > 1 M-ohm
10-31-2009, 03:26 AM
#7
It doesn't matter, to measure the coil resistance you disconnect the plug from the DME plug and measure the sensor at the sensor plug. Think of it this way, I hand you a sensor and ask you to measure the coil resistance between terminal 1 and 2. What do you get? Disconnect the plug and measure between pin 1 and 2. This will just show that the coil is OK, it does not determine if the spacing of the sensor to the gear is correct.
Why, the sensor has a magnet with lots of fine wire wraped around it. When the metal gear passes over the sensor magnet, it causes a change in the magnet field of the magnet. A change in a magnet field causes a generation of voltage in the coil (just like a generator). In order to create a 2V pulse at cranking RPMs, it was determined by Porsche that the spacing between the gear and the sensor has to be 0.8mm. This 2V spike is a very quick spike and a volt meter will not even see it, need a scope.
Why, the sensor has a magnet with lots of fine wire wraped around it. When the metal gear passes over the sensor magnet, it causes a change in the magnet field of the magnet. A change in a magnet field causes a generation of voltage in the coil (just like a generator). In order to create a 2V pulse at cranking RPMs, it was determined by Porsche that the spacing between the gear and the sensor has to be 0.8mm. This 2V spike is a very quick spike and a volt meter will not even see it, need a scope.
Last edited by Bri Bro; 10-31-2009 at 04:09 AM.
