Can this ECU be repaired? Pics inside.

[Rob_farmer]

[Fred555]

That part could be changed by somebody good at soldering Surface Mount Device (SMD)sized components you could be lucky that might get it going again or something else might have caused the component to burn out - try it.

[Brianmoooore]

Part can be changed easily enough once and if the part can be identified, and the only realistic way of doing that is to open up another undamaged one.
As Fred has said, chances are the part is a victim, not the cause.

[Rob_farmer]

Ok, goes to bin then. I burned it myself, we wired something incorrectly while fitting relays for LPG and smoke started to come out from ECU

We looked at instruction, it looked like +12 goes to ignition coil and we were wrong, cooked ECU.

[Speedtouch]

What ECU number is it?

I have a load of spare ECU parts from when I helped a pal do Megasquirt conversions, and may be able to supply the part, and could solder it in for you if you wish...

[Rob_farmer]

What ECU number is it?

I have a load of spare ECU parts from when I helped a pal do Megasquirt conversions, and may be able to supply the part, and could solder it in for you if you wish...

Thanks, but I`m not in UK. Got motronic 1.1 at scrapyard and fitted. Thought could repair it and keep as spare.

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If that would be definite get x part here and resolder, I would probably do it. But turns out its not guaranteed its gonna work as Brian said, could be something else dead.

[Speedtouch]

I have had a look at my spare circuit boards, and I have at least four of those parts - they are a 10 ohm resistor.

[Rob_farmer]

Should I be able to buy them in electronic component shops or they are something specific for ECUs? Sorry, I`m not too clever on electrics.

[Brianmoooore]

The brown wire on a LPG set up is the feed the LPG ECU uses to tell it that the engine is running. It's a high impedance connection, and I wouldn't expect it to cause problems, whatever you connected it to.
Should be connected to the plain black 'engine speed' out pin on the E30 ECU.

[Brianmoooore]

If it's a 10 ohm resistor, it'll be easiest to fit a wire ended one from the likes of Maplins. 1/4W should be adequate.

[Speedtouch]

I can supply you with the ones I have, for the price of the postage.

[Rob_farmer]

We did connect brown as per instruction. And we also connected +12 to ignition coil(squared red) because we misread(we think so) schematic. Its a bit mystery in this case. After we fried ECU, we thought we take +12 from some other place, not ignition coil, and it all works, still.

One other guy told me - it was not the cause of death of ECU, must have been something else. But we did nothing else. Reconnected +12 wire away from ignition coil, plugged in new ECU and no problems. He said: wait and you will see, your replacement ECU will cook again in future because you messed up something else, some cables must have touched where you connected 3 relays.

I don`t know, know nothing about electrics, but it works so far.

[Brianmoooore]

I expect that resistor is either connected to the source or drain of the coil driver FET, to limit the current if the ignition coil goes short circuit, which is effectively what you have done.
If you connected 12 volts + to the - terminal of the coil (black BMW wire), then the ECU will be damaged the first time it tries to fire a spark plug.
(Note that this black wire isn't the same black wire that you should have connected the LPG brown to.)

[Rob_farmer]

I`m not in UK any more(was there for 11 years) and there are no likes of Maplin here in this country. But I`m sure I can source such component.

[Speedtouch]

Well, for the price of a resistor and a bit of time soldering it in, you may have a useable spare ECU - worth thinking about...

[Rob_farmer]

Well, for the price of a resistor and a bit of time soldering it in, you may have a useable spare ECU - worth thinking about...

Yeah, I`ll give it a shot. E30 ECU`s cost about £30 here.

[Speedtouch]

If you have a multimeter, you could measure the resistor; like I say, it should be around 10 ohms. If it's open circuit, then it's obviously blown.

[Rob_farmer]

If you connected 12 volts + to the - terminal of the coil (black BMW wire), then the ECU will be damaged the first time it tries to fire a spark plug.

This is maybe what happened. Once we connected everything up, I tried to start the engine for a first time, it was turning, but would not start. I saw smoke coming from ECU. Then I tried again, smoke again(not clever, I know). We took out spark plug to check if there is a spark, there wasn`t.

[Brianmoooore]

That fits exactly. Didn't notice the Latvia bit, but I'm sure there's a local source. I pay less than 1p each for suitable resistors, so they aren't exactly an expensive part!

[Rob_farmer]

Thank you so much guys for your assistance and help this late Sunday night

[Fred555]

Well then we know the cause of the fried resistor was the modifications so there could be nothing else wrong with the ECU so it is absolutely worth soldering in a replacement. You have nothing to loose and everything to gain!

[Fred555]

Could some one (Speedtouch perhaps) please identify this Bosch ECU Resistors value and wattage?

This one is probably a Carbon Type Resistor (replacement one could be upgraded to a more temperature stable Metal Film type?).

The diameter is just under 5MM by 14mm long with a slight spiral down the side but how would you interpret those markings?

[img][img]http://i1157.photobucket.com/albums/p58 ... emoved.jpg[/img][/img]

[Speedtouch]

It will be a 0.15 ohm wire-wound resistor with a tolerance of +/- 10%, so it could have an actual value of anywhere between 0.135 ohms and 0.165 ohms.

The '1' at the end probably signifies a power rating of 1 Watt.

[Brianmoooore]

The '1' at the end probably signifies a power rating of 1 Watt.

Possibly, but it's huge for 1W. Going by the dimensions, it ought to be 2 or 2.5W.

[Fred555]

6.5Amp peak load through it dropping to 4Amps. Measuring the device it drives connected on the battery direct via an Ammeter.

[Speedtouch]

That'll be in the region of 2.4 - 6.34 Watts, according to Power = Current squared * Resistance.

Does it get hot?

[beemerbird]

I`m not in UK any more(was there for 11 years) and there are no likes of Maplin here in this country. But I`m sure I can source such component.

Elfa Distralec is probably the closest you'll get.

[Fred555]

UK Farnell P/N 1108092 or 1108078 seem to have a strangely low voltage rating of "Voltage Rating: 870mV" ???? so maybe not or does that figure not matter? - how about Farnell P/N's 9497226 or 1903888 or 1735118?

[Speedtouch]

Farnell's website is currently down for maintenance:

"Our websites are currently unavailable whilst we perform a scheduled system upgrade."

[Fred555]

That's priceless!

[Speedtouch]

It seems to be back up again now. You're right, 870mV does seem to be a very low voltage rating for a hefty great 5W wirewound resistor.

I suspect they meant 870V, since the dielectric strength is 1,000V AC.

[Brianmoooore]

Not at all! If you apply 875mV across a R15 resistor, it will dissipate almost exactly 5W. Any higher voltage would cook it.

[Speedtouch]

True, so it's almost like a fuse in that respect.

[Fred555]

Looking at the data sheet PDF for that one makes it even more unclear http://www.farnell.com/datasheets/442514.pdf "Maximum Working Voltage V (P x R)1/2" does the data sheet even agree with Farnell's website info?

But compared to the others it costs more and is also far more precise at 1% compared to 5% tolerance.


While 9497226 is listed as "Voltage Rating: 100V"

Are any of these resistors even suitable to replace the one in the photo?

[Speedtouch]

Why do you need to replace it?