Rev3 94 ecu issue

m122794 · Post by **m122794** » 16/01/22 23:39

A couple of times over the summer my engine decided to die when pulling to a stop at a junction and I didn't think too much of it. I just restarted and all seemed fine but I've also been having various random lights coming on in the dash although the car has seemed to work OK.
As the car is off the road for the winter I thought I'd have a look at the Ecu and three of the electolytic capacitors were just beginning to leak so I ordered a full set of new ones and replaced them all. The car now starts and idles perfectly.

I'm aware the rev1 and 2 ecus are having issues but it looks like the later ones are beginning to go as well so it might be worth checking yours if you have the chance. Generally electrolytic caps have a lifetime measured in hours but should last 20-25 years before giving up.

Padraig 04 · Post by **Padraig 04** » 17/01/22 13:01

What would you be looking for exactly when the ecu is open? Do the capacitors swell or is it just leaking?

m122794 · Post by **m122794** » 17/01/22 13:44

A couple of things really - the top of the can sometimes gets a bit domed but usually you can see some fluid leaking from the bottom seal where the wires stick out. If this sits on the PCB for any length of time it will etch the copper tracks away and then the repair is much more involved (and expensive if you can't do it yourself).

The ECU for my Rev3 is PNo 89661-17500 and it uses 8 electrolytic caps:

C809 10uF 50V
C512 10uF 50V
C820 15uf 35V
C004 33uF 35V
C002 47uF 63V
C101 100uF 10V
C510 100uF 10V
C105 220uF 10V

I got the whole lot delivered for a few pounds and 30 minutes with a soldering iron. Like I said previously, 3 were in a poor condition just beginning to weep and all of the rubber seals were hard so not much life left in any of them.

Cheers,
Graham

jimi · Post by **jimi** » 17/01/22 15:49

It mainly seems to be an issue with 90's capacitors, it's very rare to see similar problems with MK1 ecu's which are 30+ years old.
I've come across similar problems with capacitors in consumer electronics from around 2000, mainly seems to be psu's affected from what I've seen/experienced.
Thanks for posting your ECU capacitor list, I'll put it to KY2 , would be very useful if anyone has a list of capacitors for the other Rev ECU's.

m122794 · Post by **m122794** » 17/01/22 18:21

Yes, and I think its possibly a cost-related issue as well: you can get caps rated for more service hours at higher temps and higher voltages but the ones in my ECU were pretty-much 'bog-standard' lower rated units. The ECU gets pretty warm where its mounted in the boot of the Mk2 just above the exhaust and is covered in carpet just to insulate it even more so the caps have a pretty hard life.

All my replacements were at least rated at a higher voltage or service life than the originals.

If it helps, here's the list of the Manufacturer's part numbers of the caps I bought.

C809 10uF 50V PANASONIC ECA1HAM100X
C512 10uF 50V PANASONIC ECA1HAM100X
C820 15uf 35V RUBYCON 200RX3015M8X
C004 33uF 35V PANASONIC EEUFR1V330B
C002 47uF 63V RUBYCON 100YXF47MEFC10X16
C101 100uF 10V PANASONIC EEUEB1H101S
C510 100uF 10V PANASONIC EEUEB1H101S
C105 220uF 10V PANASONIC EEUFS1H221LB