Testing hall sensor

[AlanR25]

The responses to what2do's question in "Testing hall sender - idiot's guide" were very helpful - but before I buy a new sensor, I would like to check a few more things.
I carried out the test that bigherb posted:
Remove the centre HT lead from the distributor and hold it about 5mm away from a metal part of the engine or bodywork and away from the fuel system.
Remove the three pin plug from the distributor and probe a piece of wire into the centre pin of the plug.
Switch on the ignition and then scrape the other end of the wire along a metal part of the engine this should then produce sparks from the HT lead.
If you get sparks then the rest of the ignition system is OK and the hall sensor is at fault.
I got sparks, so the fault seems to be with the hall sensor.
Next I swapped the king lead for a plug lead and earthed the body of the plug (a bit like bigherb's video) and I still got sparks at the spark plug when I scraped the wire along the engine (but now I had an extra hand free!).
Next I reconnected the 3-pin-plug to the distributor and turned the distributor shaft by hand - no sparks this time, so fault still likely to be the hall sensor.
Then I probed the back of the 3-pin-plug (whilst it was still fitted) measuring voltage between each wire and earth and found...
12 volts at the red/black wire (outside pin)
0 volts at the brown/white wire (outside pin)
4.47 volts at the green/white wire (centre pin)
Rotating the distributor made no difference to the 4.47 volts at the green/white wire.
Is this what you would expect to find?
Finally, with the distributor on the bench, I put 12 volts across the hall sensor (+ to red/black and - to brown/white). Measuring resistance from the centre pin of the 3-pin-plug to earth, I couldn't get a circuit regardless of the position of the distributor shaft.
Have I done enough to be sure that the hall sensor is the problem?
Thanks
T25 (1983) DF Engine - Leisuredrive conversion – a charmingly retro nightmare.

[bigherb]

Then I probed the back of the 3-pin-plug (whilst it was still fitted) measuring voltage between each wire and earth and found...
12 volts at the red/black wire (outside pin)
0 volts at the brown/white wire (outside pin)
4.47 volts at the green/white wire (centre pin)

You should check the voltage across the two outside pins, the brown/white is the earth for the hall sender checking across the pins and getting a voltage reading checks the integrity of the Hall power supply and its path to earth.
Otherwise you have done it correctly and the Hall sender or its wiring in the distributor is at fault.

[AlanR25]

Thanks bigherb. I checked the voltage across the outside pins and found 12 volts - so it seems like time for a new hall sensor.
Info on JustKampers says I may need to re-use the connector from my old unit. Has anyone tried this? Is it as straightforward as it sounds? Is it best to join the wires inside the distributor or is it easier to try to solder the wires into the old connector?
It also seems you can pay as much as you like for one of these. I popped 034-998-065 into google and found prices from £13 to £68. Has anyone tried the offering by JP Group?
Thanks for any feedback.

T25 (1983) DF Engine - Leisuredrive conversion – a charmingly retro nightmare.

[bigherb]

I popped 034-998-065 into google and found prices from £13 to £68. Has anyone tried the offering by JP Group?
Thanks for any feedback.

As they are pattern parts they could all be coming out of the same factory and reboxed, until someone buys the different types and compares them we don't know.

I would replace the plug on the end of the wiring loom to the square type
.

[mgbman]

My son has a recurring fault with his 1980 Aircooled. On and off for some time now it suddenly cuts out while driving, usually after about 3 miles. When the engine has cooled down it starts fine.

Over time we have replaced engine electrics and fuel system and it settled down and was running well.

A new ignition amplifier was installed, we kept the old original one.

Hall sender is original. Coil is original.

Last Sunday on the Busstop run, the van stopped suddenly with the old symptoms. AA checked it out and said its probably the new amplifier failed. AA recovered van back to my son's home, he put the old amplifier back in and the engine started and runs fine again.

Am I right to suspect the hall sender is failing on and off, maybe when it gets hot. The coil is original and maybe that could be a suspect also.

[bigherb]

Am I right to suspect the hall sender is failing on and off, maybe when it gets hot. The coil is original and maybe that could be a suspect also.

Put the suspect amplifier back on and do the above check, if you don't get a spark then it is a faulty amplifier or coil/wiring.

[mgbman]

Thanks bigherb. The problem I have is the sudden stopping happened with the old amplifier, we assumed that was faulty and got a new one . The same has just happened with the new one. Which made me think it might be something else causing the symptoms.

Would be a bit unlucky if both were faulty.

We made some assumptions along the way when we thought fuel was the issue as the old tank was cruddy and the solex's needed refurbing and some of the tank breather was missing or leaking and my son filled up with diesel one day. So we decided it was time to renew the lot and all went well until Busstop. Its disappointing and frustrating.

But we will do the tests and maybe prove where the fault is.

[AlanR25]

As they are pattern parts they could all be coming out of the same factory and reboxed, until someone buys the different types and compares them we don't know.

Feedback - I bought J10729 from Just Kampers at £43. The label on the box said "Distributed by JP Group a/s Denmark". I followed the advice given by Tony in his review on Just Kampers and it fitted and worked fine.
However, I now have some performance issues - I don't think (hope) these problems are not associated with this part - but that's a subject for another post.

T25 (1983) DF Engine - Leisuredrive conversion – a charmingly retro nightmare.

[bigherb]

As they are pattern parts they could all be coming out of the same factory and reboxed, until someone buys the different types and compares them we don't know.

Feedback - I bought J10729 from Just Kampers at £43. The label on the box said "Distributed by JP Group a/s Denmark".

Thanks, good to know what brand the JK one is.