Hi,

I couldn't find any info on this, so I thought I let you all know what capacitors are in the power steering ECU(s). As we (should) replace all the capacitors in the main ECU, the power steering system shouldn't be treated otherwise.

This guide covers:
89650-17081 PS Computer from 07.1994 to 1999
89652-17011 PS Motor driver from 1989 to 1999 (according to my quick research)

This is not a comprehensive guide, I won't go into details how to solder and stuff.
Its a pretty easy solder job as the boards are only double sided, but be sure this is not your first solder job ever. You can rip VIAs out (interconnects between the two sides) and do other damage as well.

You need to remove the spare wheel, the plastic lining and the metal cage which supports the plastic lining (Yellow arrow) from the frunk.
Tools for removal: Flat head screwdriver, 10 and 12mm sockets

Starting with the computer (black plastic box), Remove the connector bracket (White arrow), Pry the box out which held by 3 clips (Blue arrows), Remove rubber boot and disconnect the box.

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This is inside:

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The aluminium electrolytic capacitors are:
C3 - 50V 2.2uF
C6 - 50V 10uF
C11 - 50V 4.7uF
C18 - 50V 4.7uF
C21 - 16V 47uF
C29 - 50V 47uF
C34 - 16V 47uF
C32 - 50V 47uF
C30 - 16V 47uF

Replace them all with at least 105C temperature rated good quality capacitors (Just to name a few: Panasonic, Rubycon, Nichicon, Nippon chemicon) I usually use low ESR panasonics.

Anyways, below is the reason you might consider doing this (Corrosion due to leaking electrolyte in my board form 1995)

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Moving on: Motor Driver
Disconnect the top electrical connector, remove the 3 screws (1st picture, Green arrows), lift out the box and you can easily disconnect the two remaining electrical connectors.
Remove all the screws on the box, except the 2x2 screws on the left side holding the 2 brackets.
This is inside:

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Undo the marked screws to remove the board. The rubber grommet slides out with the board and cables. Once removed, try not to put much stress on the cables, you don't want to weaken/crack the solder joints.

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The aluminium electrolytic capacitors are:
C1 - 50V 47uF
C3 - 50V 47uF
C16 - 50V 10uF
C25 - 50V 1uF
C26 - 50V 1uF

Replace them all with at least 105C temperature rated good quality capacitors (Just to name a few: Panasonic, Rubycon, Nichicon, Nippon chemicon)


The white paste on the underside is thermally conductive as the housing is the heatsink for the MOSFETs. You may change it or leave it, but don't wipe it off and assemble it without any paste.

Notes:
- I didn't measure capacitor diameter, height or lead spacing, usual size capacitors will do just fine here. Plenty of space around all components.
- You may also look around for cracked solder joints on both boards and re-solder if necessery. I found a few fishy ones in the PS ECU and a few cracked joints in my light retractor module

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- You may also support the newly installed caps with some glue, so their weight will not crack the joints due to vibration. I used hot glue sticks for this purpose. All you need is a small amount to connect the capacitors body to the PCB. Don't pot the board :lol:
- You can use higher voltage rated capacitors if only that's what you have in stock. Don't use lower voltage rated ones. This doesn't apply to the capacity rating, use the correct capacitance.

Hope it helps

Cheers

This may as well have been in a different language for me!

I'm sure someone will need it though and will be a huge help to them, KC'd for taking the time to write it up and share

Very interesting and will be helpful for someone in the future I am sure.

thanks!

Thanks guys and you are very welcome!

WOW class write up

Thanks for the good information.
Also required to do this job, good eyesight and a steady hand and I don't have either

What were the issues that prompted you to change the caps?

Simply the age of the car/parts, there was no issue.

My hobby is electronics and I know that the electrolytic capacitors are one of the weakest points in any circuit. As they fail they could cause mechanical damage to the PCB (leaking electrolyte) and could also cause failure to other components in the circuit (high ESR or even short out)

I read many threads where people were forced to change them as their main ECU stopped working due to leaking caps. Some others are do it as a preventative maintenance. I'm in this group.

As the main ECU, the PS ECU shouldn't be treated otherwise either, not to talk about the
-light retractor module
-A/C Amplifier which controls radiator fan speed in A/C cars
-Speedo, RPM gauge (5 capacitors) - Many threads about these stopped working and solved by changing the caps
-few other modules under the dash

I hope this answers the question

Cheers