ECU Capacitors

Is it C226 or C227? It doesn't make much difference but I think I saw C227 on the PCB photo.

This small cap can just be a polypropylene, as it's right next to the connector it won't be particularly important and is probably just to suppress the odd bit of noise. 16V and up all fine.

I'd source a new 1W (or 2W if it fits) resistor for that position too as it looks to have got a bit warm. We need to be sure that it's getting too warm due to the old cylindrical (electro) caps leaking power or due to another fault causing the ECU to supply too much power to something.

It looks to be C226, so a 22nF-100nF polypropylene 16V Capacitor it is.
We were already going to replace the R570 resistor and see if a 2W fits.
Many thanks for the swift reply, will keep you posted!

16V is the minimum, you are most likely to find 100V or so, just as long as it fits.
I dug out some old photos of mine and of that area, it looks the same as the other little ones nearby, just RF suppression I suspect.
So see if you can read the values.



I'm still a bit puzzled by the 'burn' in yours, never seen that before, when you take the old caps out measure their resistance (100 ohm range or similar) as SOMETHING is taking WAY too much current and it may not be anything inside the ECU.

BTW if you are doing it yourself use some solder braid and remember a hot soldering iron for short bursts, allowing the PCB to cool. Also note the 1uF is bipolar so a 1uF Polypropylene in there is a good idea too.

Gently 'walk' the capacitors out one leg per step and then when cooled clean the holes with the solder braid to clear the solder so the new ones go in. Get the the right way around . Soldering should be hot and fast like Victoria Pendleton.

Having some more looks at the diagram I have and can't seem to relate the (burned) resistor loaded connection to one on the diagram, all the outputs with resistors on seem to go to sensors, and supply a resistance to 12V or 5V. So it's possible a sensor has shorted out and that's drawing excessive current that has cooked the resistor.



In the photo you can see the small 12 pin connector, find out for sure which wire from that is connected to the resistor that is burned and see if you can measure the resistance to ground and what colour it is. The aim is to find out where it goes and to see if there is something wrong with whatever is at the other end.

If you get a connection to ground it may be possible to use a multi-meter that beeps when it detects a short(ish) circuit, and then you can try unplugging sensors to see when the beep stops (which will be the sensor you want to find). Then we'll try to see what type of sensor it is and how it relates to the diagram.

The ECU component replacement work is currently being g by a professional outfit. Theve found some damaged tracks from the capacitor leaks, which I hope they can repair too. Regarding the resistor once I have the unit back I'll follow your instructions.
Keep you posted GPW, and many thanks again.

Here are the pictures of the damaged tracks:
https://drive.google.com/open?id=1LHF91nNBNwhct3SMqKEmhYUUWwooS2FW
https://drive.google.com/open?id=1S4Twwu7wa0ORVUtSNQuHVSchOHg-ttmh
https://drive.google.com/file/d/1k0dEmnpC8N2l2RRkU1ATU37g28Na6F5d

They look like they should clean up ok, just scrape back to the copper and tin them with a bit of fresh (resin cored) solder, job done!
If you get any track breaks just reinforce them with small bits of wire - offcuts of component leads are good.

Looks like you really did need the new caps in there, but also over the weekend check why the resistor is burned or it will just burn again as noted above - looking at the pic of mine immediately showed me it shouldn't even get hot.

Do the dead caps that are taken out look like they've got hot?
Also remember the tiny 1uF electro cap is bipolar, replace with the same or a nice polypropylene like I did on mine, they are better anyway. (Polypropylene are bipolar (can be connected any way around) and work better but only come in small sizes).

Here's a picture of what it should look like:
https://drive.google.com/file/d/1U2qgZtBVX4-hzMkPQewClj4cUUUw8w2l/view?usp=drivesdk

Apparently the ECU components have been replaced but, unfortunately the C402 capacitor has been replaced with a ECWF2105JA 1854891 (PP film capacitor 250V non-polarised) and has probably been completed and conformal coated now. Is this a showstopper?

Not at all, that sounds like a good choice to me.

I think any PP cap would do the job.

That resistor overheat on the other hand is a problem..

Yes we still do need to do some tracing to see what can have drawn excessive current through that resistor. Hopefully if the ECU is plugged back in with the lid off, a finger can be applied to the resistor and if it starts to get hot the power can be turned off quickly. If it doesn't overheat we can conclude it was one of the faulty capacitors or track damage causing it, if it still does it's likely to be something external to the ECU.

Yes my money is on an external short on that line, with the incomplete wiring diagrams we have we need to see where the wire ends up. It must be a sensor I think that remains shorted out, small chance it could be a relay but unlikely you'd buffer one with a resistor.

If I had an ECU I'd trace out that part of the circuit to see which pins if any on the connectors are fed via that resistor and any associated circuitry but I don't have access to one. Hasn't anybody done any investigation of those units?

Just a note to say that the I have a fully working ECU!
After replacing the capacitors as instructed on this thread and the overheating resistor that turned out to be 10 ohm.
The tracking had corroded no doubt causing the resistor to heat up, this was also repaired, the whole lot conformal coated.
I also checked the ECU connections before assembly as instructed, all was well.
I've been using the van for a while just to check nothing is untoward, this was the reason for the delay in response.
I must pass on my gratitude particularly to GPW & JT69 for now having our van back and working happily.

Congrats Dougal nice to hear did you see my bit on cleaning your turbo pressure sensor it improves performance no end.

Brilliant news, glad it's all working well again