Door Latch/Lock Mechanism

Lotus Excel Door Handles, connecting rods, locks, latches and central locking

A collection of hints, tips and photos.

One of the Excel's main weakspots is the exterior door handles. They're Toyota parts, only used on the Celica Supra Mk II for about a year from 1983-84. Lotus being Lotus, they inverted the Toyota handles and used them on the opposite sides of the car. As a result, it isn't possible to fit the later Toyota handles without a complete redesign of the actuating mechanism.

That said, if you get the connecting rods and everything else properly aligned, the stress on the handles can be minimised and they shouldn't fail.

If you find that you have locking problems, and that your exterior handle is pulling away from the door, then the plastic that holds the insert for the clamping bolt has probably failed. Epoxy resin, a longer insert and careful readjustment of the whole mechanism is the best answer. Similarly, if your central locking is misbehaving you may have a loose connecting/pivot lever, fractured wire near the hinge, or a problem with the door handles. New handles are not available...but tightening the pivot point for the connecting lever is easy.

If you door flies open on corners, your latch has probably failed - which is a now major problem.

The system shown below is from a later car with central locking. Early cars didn't have the electric actuators and extra connecting rods, but the basic system changed very little over the years.

There's not a huge amount to say about the process of getting the mechanism aligned, except that it takes time and patience and helps to be able to visualise things based on the components off the car.

The latch mechanism is held onto the beam by 4 allen-head setscrews. On later cars, there are 3 spacers (1plate at the top and two thick washers at the bottom) between the latch and the beam. Watch out for the lengths of the setscrews. One is shorter than the others - probably best to put it back in the same place.

The next two photos show the whole latch and rod assembly, including the pivot lever for the central locking, once they're been removed from the car. All that is required to get to this stage is to pop the rod ends out of the plastic clips on the door handles and the actuator and to unbolt the lever from the inner door skin.

This is the infamous plate with the "Z" slot that converts the motion from the outer door handle & lock into the appropriate motion for the latch. Note that the ends of the rods are threaded so can be screwed in or out to adjust length.

And this is the other side of the latch where the rods from the inner handle connect to release and lock the door. Again these are threaded so length can be adjusted - BUT if you have central locking, you'll need to play around with the point at which they attach to the pivot lever too.

The rods are clamped to the CL actuating lever, inside the door skin, with grub screws. A small allen key is required to release them. The internal release rod (i.e. from the interior handle to the latch) does go where the parts manual shows it - it needs to be on the outer skin side of the lock pivot rod or there's too much friction in the system. (i.e. not where it appears to want to run naturally).

Note: When putting the lock and rod assembly back into the door, make sure that the two rods for the exterior handle come up through the beam. The big hole in the inner face of the beam means you can get fingers in to guide them. If they aren't projecting up before you attach the latch to the beam, you'll have to unbolt the latch again.

And finally, a couple of shots of the door handle from inside.

This is the latest of the version of handle - it has a single piece clamp bracket (early models have two - one at each end) and a hole drilled through the handle and bracket to take a reinforcing pin which completely fails to solve the breaking screw hole problem. It was worth a try, I guess.

And finally

  • General rule - if things are stiff or the mechanism is sticking, check clearances at the latch end. There isn't a lot of space between the rods and the window frame and a slight misalignment can cause fouling. You may need to unbolt the latch and wiggle it up and down to get enough clearance. If it's correctly aligned, you should be able to operate the latch using the long inner rods without resorting to excessive pressure.
  • You don't need to close the door to test things. A thick screwdriver or suitable sized rod can be used to rotate the latch mechanism itself, simulating what happens when the door is closed.
  • Concentrate on getting one handle working first.
  • Leave the unadjusted handle disconnected so you can be sure it isn't interfering.
  • I found it best to get the basic interior release working before worrying about the locking mechanism. I started with the interior as it's the easiest one to work on, and made sure that the grub screws on the CL lever were slack so I was only adjusting the handle to latch rods.
  • Once the interior handle and lock is working properly, adjust the central locking so that it works and you can unlock both doors from the one you aren't working on, just in case.
  • Adjusting the central locking is fairly straightforward. With the rod disconnected, slacken the mounting point on the lever and simply slide it to get the right length to ensure it will trigger both lock and release motions when the inner locking lever is used.
  • Once you're happy with that, then connect up the other handle and work methodically. Again, start with the release handle and then do the lock. The rods can *just* be rotated with the handle in-situ. It isn't particularly easy, but there's just enough space to do it with a bit of fiddling and one or two complete turns in either direction is probably all you need.
  • Bear in mind that the door should "pop" open when you pull the outer handle. You shouldn't need to pull it hard.
  • The central locking itself is a simple system with no clever control boxes. Unlocking either door causes the rods to move the actuator in that door which changes the voltages on the two signal wires which run between the actuators. Sometimes one of the control wires fractures near the door hinge, resulting in signal voltages not changing correctly. It's easy enough to check for wiring faults if you know the voltages relative to earth (end of a black wire, or pretty much any exposed metal inside the door) :
    • White/Orange=12V, Yellow/Orange=0V = Locked
    • White/Orange=0V, Yellow/Orange=12V = Unlocked