robk
Yep, you gave me that link a while ago, thanks! I am leaning towards that solid state relay. The only potential downside is that solid state relays get hot and in doing so their maximum current reduces, so I need to make sure that the heat can be dissipated. I think it should be OK with it bolted straight to the metal chassis of the car anyway. 
BTW, when I was talking to you about it you mentioned that I'll need a diode to suppress the EMF spikes, but it occurred to me that the factory power steering driver unit probably/hopefully already has a diode for this purpose. 

The SSR comes with a 2-3mm thick plate on the back side as a heat sink, if you bolt it to the chassis, it will be fine. I had no issues running ~2.5Kw of power through it in my combat robot.
 

 
In my application, I needed the flyback diode due to the drive motor being a low inductance motor spinning at ~20000 rpm, so it would generate large voltage spikes (100+v) when the motor was turned off. A simple $0.15 1D4004 1000v 1A diode from Jaycar was my savior.

Yay for robots indeed!

Others in the combat robot community have successfully run big power (kilowatts) through them for years as well. I thought I had a spare one somewhere but I just checked and can't find, sorry.

Dudeman

5SGTE
380wkw mr2 and loss of licence, wonder how that happened... Lol, sounds fun though.

Did you lose them all in one or two goes? or you still getting tickets for not using your indicators? (thats a lot of not indicating!)

It was just an accumulation of small speeding fines  I've never been booked for anything else. 

I completed the installation of a Solid State Relay to replace the original Power Steering Relay. I also installed the Ecliptech Shift-P2 progressive shift light just in time for the MR2 Wakefield Park Challenge next week. I'm very happy with how they both turned out.
 
This is the solid state relay that I used to replace the power steering relay. It's the 'SY4086' 100 Amp one from Jaycar. The original PS relay has a thick black wire and thick white wire (for the load side) and a thin black wire and thin white wire (for the input side). The thick wires already have ring terminals which can be unscrewed from the original relay and screwed straight onto the solid state relay. The thin wires need to be cut from the original relay so you can crimp on new ring or spade terminals to suit the solid state relay. As you can hopefully see in the photo, the pinout for the solid state relay is as follows:
- Thick white wire = output +
- Thick black wire = output -
- Thin white wire = input +
- Thin black wire = input -

 
This one shows where I mounted it to an existing metal plate (which can act as a heat sink) next to the fuse box in the frunk. Some SW20s seem to have some sort of ECU mounted in that spot, but not mine. Ignore the other 'regular' relay nearby in the photo with the red wires, because that's for the electric pump in my air-to-water intercooler system.

 
These photos of the Ecliptech Shift-P2 aren't very good but they'll have to do for now. This one shows how nicely it fits above the steering column without obstructing the view of the gauge cluster. The slight curve on the bottom of the unit matches nicely with the curve on top of the steering column plastic, and the the curve on top of the unit matches nicely with the stuff behind it. It looks like it's meant to be there!

 

 
I made a hole in the plastic above the steering column, just behind the shift light, so the wires could be hidden away. 

Thanks for sharing the info on the ps relay. Certainly provides a 'once and for all' solution to an increasingly common problem.

Just a small update, regarding my tail lights and brake lights.
 
The previous owner of my car swapped the later model 'kouki' rear lights onto the car, but when my headlights are on it only illuminates the outer red tail lights, and the brake pedal only illuminates the inner red tail lights. This is the same on many SW20s, and I was never bothered by this until I was on the last MR2 Club run up to the Blue Mountains, following Eddie in his immaculate SW20, and I realised that his tail lights look so much better when both the inner and outer tail lights are doing the same thing.
 
I was going through my garage today and I remembered that the previous owner of my car gave me a bunch of random stuff all those years ago, but I never looked closely at some of the things that he gave me. Well, it turns out that he gave me 4x dual filament bulbs and matching bases. Score!  Now I don't need to buy anything and I just need to connect the extra wires for the dual filaments vs single filaments.

robk
Just a small update, regarding my tail lights and brake lights.
 
The previous owner of my car swapped the later model 'kouki' rear lights onto the car, but when my headlights are on it only illuminates the outer red tail lights, and the brake pedal only illuminates the inner red tail lights. This is the same on many SW20s, and I was never bothered by this until I was on the last MR2 Club run up to the Blue Mountains, following Eddie in his immaculate SW20, and I realised that his tail lights look so much better when both the inner and outer tail lights are doing the same thing.
 
I was going through my garage today and I remembered that the previous owner of my car gave me a bunch of random stuff all those years ago, but I never looked closely at some of the things that he gave me. Well, it turns out that he gave me 4x dual filament bulbs and matching bases. Score!  Now I don't need to buy anything and I just need to connect the extra wires for the dual filaments vs single filaments.

This was one of the very first things I did to mine when I first bought it, they look much better when wired for all four lights doing the same thing.

All done