Supporting > Engine Ancillaries

Hall Sensors dying on Holt 75

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michelko:
Hi,
here are some pics of the setup.
The ignition only has two connections to the enngine. The red HT lead and the black ground. both were screwed to the engine.
The battery is an 2S Lipo so around 8V.
al the conections to the sensor were covered with shrink tube and the sensor itselv also.
That setup worked for months but suddenly started to fry the sensors.

Jo:
The battery is used in the CDI to generate different voltages, one of which is the HV for the plug so the battery voltage is no indication of the voltage going to or across the sensor.

The guys have been describing a common problem: If the ground is not earthed to the engine or there is resistance on the return then the Hall sensor may be experiencing the HV as feedback and hence going "Pop".

Time to get your resistance meter out and check the earth is a good dead short all the way to the sensor. Then measure the feed and return from the sensor with the volt function. These devices are pretty good they can normally go over 30V DC but if the earth isn't there or is intermittent the voltage will float much higher.

The fact that you have tried two CDI's tells me it is something about the mounting on the engine.... its all pointing towards the earthing  ;)

Jo

michelko:
o.k.
7.6V at the red and black lines to the sensor
0.8 Ohm between the black line of the sensor and the black line to the case also between the battery ground.

I agrre to your earth suspect, but canīt find the cause.

Jo:
0.8 Ohms is a bit high, allow for the engine to warm up its likely to move up or down but importantly it should be a dead short. The quick and dirty way to check if it is /solve the earth problem is to run an additional earth wire up and put it under the screw that mounts the sensor to the engine.

I suspect the other 0.4V from the battery is the float caused by the 0.8 ohms resistance. Have you buzzed out the wire going from the CDI to the sensor? Was it the same one used for the two CDIs?

Jo

Jasonb:
Is that connector right. looks like red and white are crossed

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