car battery & system problems,plausible?

Well now I've got 2 stories. The ecu is still suspected !!! Its got clean earths !!!, so what else is going to pull the volts to the hall sender. It can't. The relay (apparently) blew up from decay, the ecu can't send volts. The ignition switch and starter were the only 'bent' parts to note....I hope it doesn't kill this new hall sender. Well see when the things blow up this time in the of order. I can't picture were the problems from the two versions because it ran WITH these problems, fix one thing and another needs....

What do you mean the ECU can't send volts? If it's not supplying power to the Hall sensor (as I think it does), then it's faulty. But then the ignition won't work at all (no Hall signal). Of course if it's not an HKZ type of Hall or some other 5V sensor, or it gets its 5V from another source, then my comment is invalid. Ignition switches and starters won't kill Halls. Surges or intermittents might kill the ECU, but not the Hall. (Again, assuming the Hall is powered from - and signals to - the ECU.)

No, I mean it can't overvoltage...the vw guy said it wasn't the ecu giving the volts its the (dead) relay allowing it. Isnt there a resistor or something or not enough power to the sender?

So he's saying it's a relay that supplies power to the Hall sensor? So it's a 12V (say 8-16V) sensor?   I wonder what type it is? And which relay supplies 12V to the ECU? If it's a 5V sensor, a voltage regulator is required, not a resistor. It could be a resistor-Zenor (diode) regulator, but why bother with that when an ECU has a proper 5V regulator?

..well that's interesting but I think my question to him was about 'what shorted the sensor out' and he would've replied in a sense that the parts involved being that an ecu and immo and starter aren't capable of producing the problem I'm experiencing, so I asked what killed the relay and he said 'decayed'. What caused the ecu to kill the hall sender, it can't. So "I" looked over the vehical and found the smashed planetary, maybe its grazed motor on the (magnets) outer case caused the elecy surge at starting, I also changed every elecy part that might pass or be broken by an over voltage and the similar question ALSO relates toward a cause for it, but this side of it suggests it was starter that blew up the sensor via a surge through the system. Probably killing the entire thing for all I know. Just because 1 relay was on its way out is purely coincidental but not out of the question, Normally; but the right answer stems from a car parts capability to inflict a surge. the vw mans advice is right, but I'd start with what's broken and relate from everyone's advice. It just needs 'Twisting' to be from a surge from a starter motor which works regardless and how another part 'could' transmit voltage through to other parts. As well as individually. The ecu will now go for testing, although your advice seems to base itself on 5-7v capability only...but I don't know. I guess if its connected then its broken!. My van the circus.

Also I can't say the starter caused it because evidence of black scorching wasn't there indicating arc. It was just the only visible thing broken.

The ECU operates off the vehicle's +12V. Relays fail. Various reasons. But simple to check, else replace with compatible relay (eg, SPDT instead of SPST; normal relays as emergency for tachometric VAG 5-pin Fuel Pump relays. So the Hall sensor is protected from external connection to +12V or GND, or it is supplied from 12V and its output to the ECU (usually GND, occasionally +5V or similar) has ECU-to-Hall protection, or... Cool. I'd like to see the relevant wiring diagrams... "Failure" surges are unlikely to be an issue since surges above 200V are considered normal anyway. IMO any "automotive" 12V device should (typically) tolerate 16V in addition to spikes of (typically) 400V - or higher. Critical or expensive automotive +12V systems must allow for such norms. Most automotive equipment meet or exceeds such norms. Tho Starter Motor faults are not the norm, their spikes are usually not much higher than common relay spikes. It's more likely resultant voltage dips that cause problems like "brownout" damage or overcurrent damage to the battery & wiring. Power cycling & intermittents can cause arcs or blow equipment. But a big spike blows insufficient protection. Inductive and digital circuits tend to be far more prone to failure (keep Power cycling your PC or batteryless laptop on & off...). Analog components & circuits usually fare better.

Whatever it is has got me, 4-5 hall sender's at $130 each....that's no good. Checked the loom, no burned wire. There was a 4 way join with other parts on brown wires, which enter the cab. I thought of separating the dizzy link but I'm not sure what's in the cab. Ecu gets sent off for a week in the Bahamas. Heres an exact symptom..the key turns and the starter cranks over for a good 45 secs and start stalls. Try again and no start. There isn't another chance as the hall sender is now dead. ??who knows.

The Hall sensor has nothing to do with cranking - unless some cranking limiter or (post start) cutout is involved. 45 seconds of cranking can be enough to discharge some batteries tho reasonable self- recovery (SOC or reserve power increase) often then applies.

I guess its the ecu then. One blown transistor allows over voltage (joking), or the vehical poles are reversed. Got the new sender, will let you know. Is there such a thing as a 'too cheap' sender?.