ECU known failure points

[markb_1303]

My car is currently at the spray booth. I just took a little visit and they said the car won't start. It was blowing Fuse 27 so I tried a few things and eventually removed the ECU and no more blowing. Got it home to open it up and found this thread (and the sister thread that was originally investigating the issue).

D900 and D901 have also gone on my ECU so I will be purchasing more. I found the D901 at farnell in stock (https://uk.farnell.com/stmicroelectr...-15/dp/3214566) but they don't have the uni-directional version (D900) so I will have to get a comparable part.

I'll report back once it's repaired and back in the car.

They had a jump-pack on the car as the battery had gone flat. i wonder if this could have over-volted the ECU somehow?

[gmac78]

There seems to be a lot of ECU failures related to these diodes lately. For me D900 just failed in service, I hadn't jumped the car etc was just driving along and cut out.

I'm still waiting on a pack of D901's to arrive, taking ages, however I did get some D900's so I can always send you one if you like. Think it was a pack of eight I bought.

Cheers

[markb_1303]

There seems to be a lot of ECU failures related to these diodes lately. For me D900 just failed in service, I hadn't jumped the car etc was just driving along and cut out.

I'm still waiting on a pack of D901's to arrive, taking ages, however I did get some D900's so I can always send you one if you like. Think it was a pack of eight I bought.

Cheers

Mine should be at my work tomorrow but I'm heading on holiday so I don't know if I'll get chance to pick them up before I get back. If I do, I'll send you one of each

[newsh]

My car is currently at the spray booth.
They had a jump-pack on the car as the battery had gone flat. i wonder if this could have over-volted the ECU somehow?

The jump pack could have done it.

Or did they do some welding??

[markb_1303]

The jump pack could have done it.

Or did they do some welding??

No welding but it's a good thought.

They said they started the car on the jump pack and drove it back in the shop, turned it off and took the rear light clusters out (from tailgate) and then it wouldn't start. I can't see anything other than the jump pack. It's pretty unlikely the alternator regulator would suddenly fail and I can't think of much else.

[Ian Simmonds]

The jump pack could have done it.

Or did they do some welding??

Absolutely.
Our Ur came back from its restoration with a fried ECU even though we did ask them to remove the ECU unless it was needed to drive it. Anything like welding, jump starting, rapid charging or lightning strikes instantly kills vintage ECU’s.

[prj]

That diode is the overvoltage protection diode and it blows when the voltage in the electrical system briefly reaches around 20V.
If it didn't blow then the entire ECU would have been trash.

If you have jump starters or similar that have so poor voltage control, that they generate 20V spikes into the car's electrical system, they're best thrown out to the scrap heap!
Imagine if you have a more modern car and blow a bunch of controllers there.

When doing any welding on any car it is common knowledge that you must disconnect the battery terminals!

[markb_1303]

So I was supposed to collect my car from the spray job today and guess what? I've come away with no car but a fried ECU instead (again).

The battery had been left so was totally flat and they tried to jump it which, once again appears to have blown the protection diode(s).

Be careful when using jump packs guys...

[gmac78]

Oh no, not again!!! Hopefully a quicker fix second time round.

[newsh]

So I was supposed to collect my car from the spray job today and guess what? I've come away with no car but a fried ECU instead (again).

The battery had been left so was totally flat and they tried to jump it which, once again appears to have blown the protection diode(s).

Be careful when using jump packs guys...

Blimey, that’s really unlucky :-(

[markb_1303]

It was the bidirectional diode that has blown both times.
very simple to test in situ and replace and the car is now running again!