EPAS Cut-out switch

The MGF combined a number of novel design firsts when introduced to the motoring public in 1995. It was, for example the first small, affordable, mid-engined convertible sports car. With this layout brought certain design challenges - not least as to how to provide power assistance to the steering (a marketing necessity these days) where the traditional source of hydraulic assistance, the engine, is placed so far away from the steering column. The solution was Electric Power Assisted Steering (EPAS) - a solution only previously found on the relatively exotic Honda NSX. Thus, the first 'mass' produced car with EPAS was born.

Whilst EPAS was a brilliant solution to a whole host of design problems, and proffers a number of very real advantages over hydraulic assistance (reduced energy consumption being one), early releases of EPAS attracted criticism from motoring writers and enthusiastic drivers alike. The problem was whilst the system reduced assistance with increasing speed, its interference at low speed robbed the driver of a significant degree of steering feedback. For this reason, a significant number of 1.8is were specified pointedly without EPAS, and MGFs that venture onto the track usually have the system switched off.

Switching off the EPAS on a car so equipped does have a surprising effect on steering feel - in low to medium speed corners, the steering has more weight and markedly more feel. However, disabling the EPAS by removing its main power fuse is hardly convenient when you come to park the car. Some may recall the TV adverts for the Fiat Punto - the one where boy chastises the presence of what he referred to as a 'girlie' button: a button that could switch the power assistance on or off. Thus seeded the idea for the EPAS cut out switch discussed here.

Will Munns has provided the information detailed here:

A - cable to EPAS ECU (green wire). B - cable to instrument panel (pink wire, blue tracer). A' - cable to fuse #1 (green wire). B' - cable to EPAS ECU (pink wire, blue tracer).

The EPAS Over-ride Switch

The air conditioning air re-circulation switch (part # YUG 101720) is a toggle switch, so it stays in whichever position it was left in. With the circuit design shown here, you can chose to wire the relay to positions 3 or 4 on the switch, to chose whether to have the switch warning light-on, PAS-on or switch warning light-on, PAS-off combination.

Unfortunately the switch will only fit into the passenger side blank because Rover have keyed the switches and their apertures. However, you could remove the keying with a small file so the switch is closer to hand for the driver.

The EPAS Over-ride Relay

The fuse protecting the circuit is 10A, but the signal is only used (according the wiring diagram) to switch on the EPAS, so if you are feeling really excessive then a 10A relay would be the one of choice. Maplin do a good selection of relays for under £5 (keep going through the catalogue until you find one that is in stock). You can probably get away with a 1 or 2 Amp relay, but I would play safe and buy a 5 Amp version. The relay is mounted locally to the EPAS box; there are a few screw holes that are suitable for cable ties in the vicinity. This also it means that there are only two long wires: the black ground cable to the relay and the green wire to the EPAS (needed for illumination). The other wires are sourced locally (red/black and black can be sourced from any of the other switches).

 Parts:

Switch (#1): Part number YUG101720

Relay (#2)

Connectors

Wire

Assembled together they look like this:

Fitting: 

Remove the glove compartment, from the foot well looking directly upwards you should see the EPAS ECU (electronic control unit)

  A closer look at the wires:

Points to note:

  • Green wire, supplies ignition current to system, this is the important wire!

  • Pink/Blue wire supplies instruments with EPAS OK signal.

  • Blue/Pink wire supplies power to the EPAS clutch, included so be sure NOT to confuse it with the Pink/Blue wire!

 

  View from behind the switches:

Points to note:

  • Any black wire for local GND (short black wire on assembled unit)

  • Any red/black wire for local illumination.

  • The long pieces of cable only ever carry enough current to switch on our relay (blue wire) and enough current to switch on the 'active' illumination (green wire), so you should be able to get away with damp string for these!

  • The shorter wires still don't take much current, but I would get some reasonable wire for these (use mains cable if you are desperate), and remember that you don't need lots of different colours, because when using bullet connectors they can only be connected the right way around!

Verdict:

With the EPAS override car feels better around roundabouts and low/medium speed corners (fast ones are no different). But it is very nice just to hit a button and the parking becomes a breeze ;-)