They're amusing when they work, but when they don't, I reckon they must be the greatest source of consternation amongst Wedge owners... but it's not rocket science!

The headlamps (bog-standard 7" 60/55W halogen reflector/ lens units with replaceable bulbs) are mounted in fibreglass pods. The pods hinge on two bolts that screw into captive nuts glassed-in to the shell, each side of the pod recess. Usually the bolt heads are cross-drilled to allow lock-wiring the bolts to prevent them unscrewing themselves.

Each pod has its own lift motor, mounted on a steel bracket that, depending on model, year, which way the wind was blowing, is bolted to either the floor of the pod recess or the front wall of the engine bay. If the latter, you can see the screw heads when you open the bonnet. The motor itself is as used on the Triumph TR7 and Lotus Esprit, however the bracket is a TVR fabrication. To all intents the motor is a windscreen wiper motor that goes back to at least the E-type Jaguar, modified (at casting level) by Lucas for the purpose of lifting headlamps (it has two 'park' positions instead of just one) and can be serviced in much the same way. I've created a stripdown sequence for the pod motors in case you need or want to tinker!

The motor is tied to the pod by an operating arm and an adjustable link: again depending on the car, the link can be constructed in a variety of ways but the essence is to allow a degree of adjustment to get the pod flush with the bodyshell when retracted. Be aware that if you alter the link to change the height of the pod when raised, it won't close flush. Also note that the crank arm fitted to the motor spindle was supplied in different lengths for different applications; it's stamped with a number like "1.782" which is the distance in inches between the spindle axis and the operating pin centre.

Most people are fine with the mechanical aspects of the pod system, it's the electrical operation that stumps them. Here goes...

Firstly, the motors only rotate one way, they do not 'reverse' to make the pods retract once extended. So there is no 'polarity reversal', unlike say, a window lift motor.

Each motor has a simple switch and two diodes in the wheelbox. The switch has a common contact and two 'outputs', to each of which are soldered the diodes. The switch contact is a simple copper strip. The common supply terminal is riveted to the strip, this provides one of the potential trouble-spots as the rivet can corrode and lose its connection to the strip. Next in line for grot are the contact pads at each end of the strip. These should be cleaned of corrosion, arcing deposits etc. The two diodes are common silicon rectifiers of the '1N4000' family - 1N4000 to 1N4007, but anything of similar ratings will work.

Before we move onto the flow of electrons, can I just point out for owners of other cars using these same lift motors: there is NO definitive circuit diagram for how to power them. Triumph, TVR, Lotus and Reliant (on the SS1) each came up with their own interpretation of the supply requirements. So don't use what's here (for the TVR) as more than a guide to what's going on elsewhere.

Three relays are used for the basic lift/ lower switching. Further relays are used on cars with extra driving lamps, but for our purposes we will consider a straightforward installation as used on the earlier Tasmins. Reference should be made to the circuit diagrams which illustrate the flow of current at the various points of the lift/ lower cycle. Note that some colour coding of the wiring may differ from your car. I've coloured red whichever wires are 'live' (ie at 12v) for each part of the cycle:

1. Lights are off. 12v appears on the Whi/Yel to each pod motor but can go no further as the motor's internal switch is open.

2. Lights are on (Low Beam). A 12v feed appears at one of the two diodes feeding the coil of the Headlamp Motor Control relay. This causes the relay to change over and it applies 12v to each pod motor via the Whi/Purple wires. Passing through one of the motor internal diodes and the closed switch contact, it is fed back to the coil of the Motor relay. The Motor relay changes over and applies 12v to the motor itself, which then starts to lift the pod. Note that the motor's internal switch stays closed during the lift cycle.

3. Is the same as 2. but shows main beam selected instead. This is why the two diodes feeding the Headlamp Motor Control relay are so important. If either fails the pods won't lift although the lights will be on. Someone asked how come the pods don't drop as you switch from dip to main beam and vice versa, since there would momentarily be no feed via either diode to the Headlamp Motor Control relay. The answer lies, I think, in 'flux remanence' or 'back-EMF', in other words for the split-second it takes the switch contacts to change over, the magnetic field created by the relay coil doesn't have time to completely collapse so the relay stays on. It's definitely not a function of the Lucas column switch, i.e. there is no 'make before break' action - it's a simple snap-action switch where the moving contact shifts rapidly from one fixed contact to the other - and can be seen to do so, as it's not a sealed switch.

4. The motor has lifted the pod and at this point the internal switch changes over. This breaks the feed to the Motor relay which drops out, disconnecting the pod motor.

Knowing the cycle of operation, it is possible to fault-find on the headlamps fairly rapidly.

The presence or absence of either main or dipped beam can be a clue as to whether the pod motors themselves are faulty: a defective ‘Lights’ switch or column dip/main/flash switch can make it appear that the pods are faulty. Simply peering into the headlamp recesses to see if the headlamp bulbs are lit will help here!

Now, whilst the foregoing is probably enough to help you fettle an early Wedge, things got complicated when the later cars acquired driving (or fog) lamps, some legislation changed, etc. etc... so you may need: