the flyin' scotsman

thx Colin........got a variable pwr supply but no scope.

BTW........do you have PEMs?

Lizard928

I have two sets of PEMS, both currently installed in brains.

jcorenman

Malcolm, PM sent.

Cheers, Jim

John Speake

You should be able to test with a DVM.

the flyin' scotsman

Is there a simple continuity test John?

The spare HS is on the bench and has a 3 lead connector

Hilton

edit: doh just saw John's reply on the next page I have a variable PSU (adjustable volts and amps - good for electroplating) so might have a play with setting up a test on the bench next weekend.

Hmm.. good question. I've got one I removed from my '89 due to an intermittent fault, which promptly still occurred with the brand new sensor (it was a harness routing problem).

My 87 is showing no hall signal in the ECU fault codes, so I'd like to test the old (probably good) one before the painful fitting process.

jcorenman

I did some checks on a toasted Hall sensor (crumbled connector, the sensor is fine). And yes, checking it on a bench with a voltmeter works fine. It is a simple voltage output (not a pulse) when a piece of steel (not aluminum) is inserted into the sensor gap. The sensor has a small magnet on one side and a hall-effect sensor on the other to detect the magnetic field. Inserting something magnetic (e.g. the steel disc that lives behind the cam sprocket) interrupts the magnetic field and you get a voltage output.

Here's what you need to do:

First, identify pins 1, 2 and 3 on the Hall-sensor connector. There should be numbers on the connector body, pin-1 (red wire) connects to a 12v supply, pin-2 (green) is the signal out, and pin-3 (black) is ground. On the harness side pin-1 connects to a red/white wire, pin-2 is the center conductor of a shielded wire, and pin-3 is the shield (and ground).

So (with power off) connect the positive output from a 12-volt power supply to pin-1, and the negative output to pin-3. Do not reverse this, or short the positive connection to to pin-2, I am sure that will fry the sensor.

Then connect the positive lead from a DVM or multimeter (in volts mode) to pin-2 of the hall sensor, and the negative lead to ground (pin-3 or the power-supply negative output). Do this with power off, and use clip-leads and tape to make sure nothing gets shorted. (If you are a klutz then adding a resistor in series with the 12v power-supply connection will provide some protection -- a few hundred ohms should work fine).

Now power up the supply and check the voltage on pin-2, it should be close to zero volts (0.1v or less). Now insert a small piece of sheet steel (not aluminum) in the sensor gap, that will interrupt the magnetic field and the output on pin-2 should read around 2.6 volts. If so, the sensor is working.

When connected to a EZK, the output goes from zero volts up to around 5.0 volts. This is because the EZK has a pull-up resistor from the Hall-sensor output to +5 volts. If you measure the harness connector with the hall sensor disconnected you will find 12 volts (approx) on pin-1 and 5.0 volts on pin-2, that is the pull-up resistor (I measured about 2.5K ohms). So to exactly duplicate how the Hall sensor is used, you would need to provide a 5-volt source (a voltage-divider would work fine, a 680-ohm resistor to your 12v supply and 470 to ground), and then a 2.2K-ohm resistor to the pin-2 Hall sensor output. But just checking the pin-2 output should work fine, it just won't be 5.0 volts.

WallyP

Great post!

the flyin' scotsman

many thx Jim.......will get back to it on the weekend and report

kurt_1

Can confirm that it does
"Tested" it and fried my Hall Sensor! Make sure that you got the right terminals and no pins shorting especially when measuring through the EZK connector!

Kurt

Hilton

Thank you Jim for that excellent write-up.

Turns out my old sensor doesn't work, so I don't have a spare after all