05 DS keeps burning up speed sensors

[Sergio]

Originally Posted by greg-g

If the diode is missing or open and the collapsing coil of the solenoid sends a high voltage pulse on the negative line it could easily take out the speed sensor rated at 30 V.

The collapsing field of a solenoid does not generate high voltage, it is an inductor and it reacts against change in current only.

What happens is a combination of the solenoid coil trying to keep the same current flowing as before it was interrupted and the device (switch or semi-conductor) that is interrupting the system starting to become a very high resistance.

Since Voltage = Resistance x Current and the resistance increases, it creates a high voltage across the device that it is interrupting the signal.

The diode installed across the solenoid coil provides a path for the current generated by the stored energy in the coil to circulate when the power is interrupted so the interrupting device does not get subjected to this condition.

[NoleFan4Ever]

Well look at it like this. The collapsing field of a solenoid does not generate high voltage, it is an inductor and it reacts against change in current only.

What happens is a combination of the solenoid coil trying to keep the same current flowing as before it was interrupted and the device (switch or semi-conductor) that is interrupting the system starting to become a very high resistance. Since Voltage = Resistance x Current and the resistance increases, it creates a high voltage across the device that it is interrupting the signal.

The diode installed across the solenoid coil provides a path for the current generated by the stored energy in the coil to circulate when the power is interrupted so the interrupting device does not get subjected to this condition at all.

Oh shucks, looks like Sergio typed faster then me...Lol! Gotta love a good laugh Sergio....

[Fairtax4me]

Check the solenoid for continuity across the large posts with the cables removed. If the solenoid is welded stuck the controller also puts the cart in limp mode.

[greg-g]

Originally Posted by NoleFan4Ever

Well look at it like this. The collapsing field of a solenoid does not generate high voltage, it is an inductor and it reacts against change in current only.

What happens is a combination of the solenoid coil trying to keep the same current flowing as before it was interrupted and the device (switch or semi-conductor) that is interrupting the system starting to become a very high resistance. Since Voltage = Resistance x Current and the resistance increases, it creates a high voltage across the device that it is interrupting the signal.

The diode installed across the solenoid coil provides a path for the current generated by the stored energy in the coil to circulate when the power is interrupted so the interrupting device does not get subjected to this condition at all.

Oh shucks, looks like Sergio typed faster then me...Lol! Gotta love a good laugh Sergio....

A flyback diode is a diode connected across an inductor used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted. It is used in circuits in which inductive loads are controlled by switches, and in switching power supplies and inverters.

[Sergio]

Originally Posted by Fairtax4me

Check the solenoid for continuity across the large posts with the cables removed. If the solenoid is welded stuck the controller also puts the cart in limp mode.

I thought he said he already replaced the solenoid, but It must have been another thread since I don't see the comment.

I also assumed his comment about the failed speed sensors were based on the push test.

Hopefully that is the issue since it is a lot cheaper than a Controller.

[greg-g]

No he said he checked it and it was OK so yes that more than likely is the controller

[Fairtax4me]

I don't see where he said he tested the solenoid.

Symptoms sound speed sensor/circuit related, but the sensor is obviously working at least when he tested the output of the sensor and it was pulsing. Maybe it works that much but is not producing a consistent signal when the cart is driving. Would need an O-scope to figure that out for sure.

It may be too coincidental that the solenoid sticks closed, and then suddenly opens and works properly again for a short time after replacing the speed sensor, but it's possible the first sensor was a dud, and now the solenoid has failed. It's at least easier to test than the controller, and would verify if the controller is the issue.
Another option could be damaged wiring or corrosion inside the connectors of either the controller or the sensor.

[Sergio]

Just push it to see if the sensor is working, like Fairtax4me said, test the continuity to see if the solenoid is stuck.

If no continuity, do a test drive but only press the accelerator once and see if it goes fast.

[mwollerman2011]

thanks for all the input on this issue i will check the solenoid as soon as i can. im in south florida so right now were in storm prep mode and do not have time to work on it i have extra solenoids on the shelf ill swap it out if i have to as soon as i can get back to the cart i will update this thread thanks again

[Fairtax4me]

Good luck with the storm coming! Stay safe man!