Resistor pack

The resistor pack is a very simple device which allows multiple fan speed settings from the same nominal 12V input. It has three 12V inputs and a single output, which is the motor feed.

Unfortunately due to the position Lotus have located the resister pack it is prone to high corrosion leading to eventual failure. The majority of failures are with the electrical crimp connections on the resistor pack and not the internals of the pack itself. Either way it needs to be replaced to restore full fan functionality again.

Old and new resistor pack. Note corrosion on motor feed.
Some old packs look worse than others!

Any loss of single, multiple or all fan speed controls indicates resistor pack failure. You may loose a single fan speed setting earlier than another, but the most common connection to fail first is the motor feed leading to an abrupt loss of all speeds.

Dealers may suggest this fix requires them to remove S2 front clamshell, but the following guide will show how it's possible to replace the pack through the passenger service panel.

Lotus have released a modification kit which relocates the resistor pack inside the heater matrix, avoiding future corrosion, but this will require the removing the front clamshell.

Resistor pack part number: A117P6000S
Modification kit part number: A120P0148S

DIY Replacement via service panel (non a/c only)

Click on each image for related installation notes. No two cars seem to have exactly the same parts/brackets/wiring/piping, but you'll get the general gist.

Installation of Lotus Exige S2 heater fan fix : Cars with Aircon

Requires : 1 x Heater fan resistor replacement package (Elise S2) (A120P0148S) Time : Around six hours to complete this job. Clamshell removal is the starting point.

Basic Steps :

Discharge the aircon system from service point (requires removal of right rear air intake duct behind door).
Remove front clamshell, water cover, wiper motor bracket and fuse box.
Loosen wiring loom and disconnect HVAC thermostat and fan motor.
Remove large air hose / duct from outlet of heater maitrix (top) to car vents.
Remove air con hoses to and from expansion valve (located on top /rear of heater matrix)
Gently bend the brake hose from master cylinder up and out of the way.
Remove vacuum hose from servo (pull out the rubber stopper from servo case with hose)
Remove water hoses into heater matrix (gently, the hoses will feel welded on but the connecting pipes are only packed into the top of the box with silicon sealant).
Once clear as below, you should be able to unclip the heater assembly from the fan and withdraw the heater and evaporator unit diagonally in one piece.
Remove the heater fan unit from the car. It is not unusal to find the floor of this chamber, flooded, we will drill holes later to fix this.
Remove silver resistor block from fan unit and discard.
This is a good time to apply 12v direct to fan motor to ensure that motor is operational before you go to all the trouble of re-installing a defective one.
Installation of the lotus modification kit per other instructions on this page and the technical service bulletin that comes with the kit. Assemble the heater fan and modified HVAC unit together and test for fit.
Drill drainage holes into the 4 corners of the front HVAC chamber if you have not already done so.

Installation is the reverse. First locate the heater fan into oen end of the HVAC chamber. Then install the heater unit - NOTE : there is a small a/c drainage hose that needs to be reconnected to the bottom of the heater matrix whilst inserting the unit into the car.

Finally, clip the heater and fan assembly together in situ, reconnect all hoses for water and check for leaks.

Repressurise aircon and check for leaks (mine leaked at the mounting point where the aircon pipe from the sill connects to the front pipework).

Finally reinstall clamshell and other components per the service manual.