VB921 Burned

Bad_Dog · Post by **Bad_Dog** » Fri Apr 07, 2006 1:24 am

Yesterday something strange happened.
I was experimenting with ASE. The car started OK. Then I stopped the engine, disconnected the laptop and tried to start it again.
After cranking for 10sec. i stopped and left the key on contact - then LED 17 remained on and the VB921 connected to it burned immediately.

The code was 29g1 on MS'n'Se Board 2.2. MT was not connected

So, I was wondering whether using a capacitator on the Base to pass only the impulses can protect the VB921?

Post by **jsmcortina** » Fri Apr 07, 2006 5:48 am

Sounds like you do not have "spark output inverted". Additionally take you coil+ from the fuel pump relay. This ensures that no current can flow when during "key on, engine off"

James

Bad_Dog · Post by **Bad_Dog** » Fri Apr 07, 2006 6:25 am

Spark inverted was "Yes". The engine started several times and it was OK. Then suddenly VB921 burned.

I'm actually using great part of the OEM harness and moving the coils to the FP relay is not so easy. However the VB921 burned even before i heard the click from the FP relay so it would have died anyway.

Post by **jsmcortina** » Fri Apr 07, 2006 9:30 am

Bad_Dog wrote:Spark inverted was "Yes". The engine started several times and it was OK. Then suddenly VB921 burned.

I'm actually using great part of the OEM harness and moving the coils to the FP relay is not so easy. However the VB921 burned even before i heard the click from the FP relay so it would have died anyway.

That's odd. When we first started using the VB921, RyanPzz did some endurance testing and had a VB921 on current limit for 30 seconds before it failed.
The FP relay should turn off within 2.5 seconds of no cranking or about 0.5seconds during run. So the VB ought to be fine.

How good is your heatsinking?

Fitting a capacitor to the base will likely do strange things and I would not advise it.

James

Bad_Dog · Post by **Bad_Dog** » Fri Apr 07, 2006 11:17 am

jsmcortina wrote: That's odd. When we first started using the VB921, RyanPzz did some endurance testing and had a VB921 on current limit for 30 seconds before it failed.
The FP relay should turn off within 2.5 seconds of no cranking or about 0.5seconds during run. So the VB ought to be fine.

How good is your heatsinking?

Fitting a capacitor to the base will likely do strange things and I would not advise it.

James

Thanks, James.

The VB's are put on the top of the MS box(inside). The VB burned for something like second ot two with blue smoke and typical smell. it might have been a faulty VB.

Today after driving for an hour I took out the MS box and opened it. The VB were pretty cold on touch.

Bad_Dog · Post by **Bad_Dog** » Fri Apr 21, 2006 12:37 pm

Today I burned one more VB921.
After driving the car for 2000 km without any problem I burned one more VB921 during cranking. Currently I'm using 029l code. When using 025 style wheel decoder the starting is hard.
I have two coils and two VB's respectively. However, only one of them died (Spark A). I have no reasonable explanation. After I changed the damaged component I started the car with MS box open. Touched the VBs - they were cold.

MS V2.2; 029l; LM1815 wheel decoder; dual VB921;

amd is the best · Post by **amd is the best** » Sat Apr 22, 2006 9:25 pm

I have burned several as well. I have recntly heatsinked mine better and put some thermal compount between the vb and the case. I also turned down the dwell times. That seemed to help a lot. Nick