The Lotus Grand Tourers

On startup Im getting one or two swipes of the wiper when the wipers are switched off. ( but not every time ). Clearly Im getting some backfeed from somewhere..... anybody got a clue ?

Bash

Is there a diode in the feed circuit nearby?

Could it be due to an ageing diode breached by occasional large current surges on start-up?

Or the wiper auto park mech/circuit is faulty?

Just rethought this through. It must be switch or module side. Nothing to do with supply.

Check relays for water ingress

I seem to recall this being a symptom of a poor earth connection, possibly for the engine (earth strap to subframe)

I get the same, not got around to investigating it yet. Also get it sometimes over bumps.

In the case of Zag's I'd suggest John's / Angus's idea about the switch/ loose wires.
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More general
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Been though the relays and the earth is good. Ive noticed that the wiring diagrams show a wiper relay instead of a module tho, perhaps there is a relay in there but its not immediatly obvious. Im going to look at the wiring for the motor and try and trace the feed, its painful watching the blade on a dry screen.

Bash

Could it be the motor end of travel switches not breaking? Dry screen friction holding it off?

If you Disconnect the wiper switch does it still swipe?

Yes, I've had this too. I noticed that it seemed to occur when the car had been standing for a while, perhaps when the battery charge had dropped a little. It's a quirk rather than an annoyance so I've never got to the bottom of it, but would be interested to find out the cause.

Well, I found this rats nest pushed under the dash. Its full of clipped in joints and crap connections. Ive had the car for well over 20 years and Ive never noticed this lot as most of it was pushed under the dash centre, it all appearsto be from an alarm that a previous owner had fitted, if it was a professional build they want shooting, how the car didnt end up in flames is a mystery. Needless to say its all gone now and the butchered wires sorted properly. I was going thro the wiring to try and find the fault when I saw this and got sidetracked but the switch and column wiring appears to be good, so the investigation continues.
I found that the wiring diagram in the manual has some shortcomings in that the wiring colours are wrong at the column, I will put this in a seperate post.

Bash

Defo worth getting all that crap wiring out. I hate bad wiring!

Pete

I don't have a direct answer that will positively fix the un-intended wiper action, but here are a couple of cheap things to consider.

1) Most Lotus of that period had what they called a "Drop Out" relay. While starting the engine, the Drop Out relay switches Off all non-essential circuits, diverting all available current to the starter motor. A 'lot' of circuits converge to that one point, and when it fails or develops continuity problems, a lot of funny things start to happen... aka, "sneak circuits".

A friend's Esprit SE once developed a list of electrical quirks, including a serious one in that whenever the ventilation fan was switched on, the ABS brakes quit working. Just finding that oddball relationship took a long time, then 'how the heck' could those two circuits possibly be related? Well, they were both routed through the Drop Out relay. I replaced the Drop Out relay, cleaning all connectors in the process, and that fixed the Fan/ ABS relationship, and a lot of other odd things also went away.

Now, one of my first steps when trying to exorcise spirits from a car's electrical system is to replace the Drop Out relay, and clean all wire connections in the process. For the minor cost of a relay and a little time, I eliminate a lot of possible distractions (and maybe even the root problem) before digging deeper into the wiring rat's nest.

2) Related to that same idea, each relay terminal has two connections. The wire connects to a terminal on the socket, and the relay plugs into the socket. Two connections in series within a half inch/ 12mm or each other. Many people think of cleaning the relay terminals, but never consider the socket terminals. Clean them both.

3) Pacer Technologies makes the ZAP brand of super glues... and a product called 'Rail Zip 2'. It's for cleaning and preserving the electrical continuity of the brass rails in model railroad layouts. Go to a hobby shop near you, and ask for it. It's usually on the same shelf with the super glues, but ask in the model train section as well.

It's great for cleaning off corrosion from copper/ brass terminals and connectors, then preserving continuity going forward. Sockets, bullet connectors, spade terminals, relay sockets... it's great stuff for cleaning them all and eliminating ghostly continuity problems. I've got a bottle or two in my shop all the time.

4) The wiper circuit is an odd duck. With a light, there's power, a switch, the bulb, and ground... how hard can it be? The wiper circuit isn't that simple, and it's not intuitive. Lucas published a manual called the "Lucas FAULT DIAGNOSIS Service Manual". Google it, there are PDFs available for download on the internet. If you can't find one, ping me your email address and I send a copy to you. It contains a 3-page section on Lucas Type 14W, 15W & 16W Wiper Motors, typical circuits, and de-bugging. Your car's wiring harness may be screwed-up enough to be the problem, but it wouldn't hurt to fully understand the quirks of the wiper motor and it's circuit.

5) The Fault Diagnose manual also shows an diagnostic connector that plugs directly into the motor's socket. Nothing magic, it's just a standard Lucas wiper plug like the one in your car's wiring harness. But it has a few short wire leads attached, and greatly facilitates probing the circuit and jumping power to the motor to test it's function (ie, is the motor the problem, or your car's circuit?). The plug alone is readily available for any Lucas electrics supplier, and you add a few wires yourself.

Good luck,
Tim Engel

Cheers Tim, I will have a work through those points. Ive recently had a purge on old relays but not that one so its a good place to start. It does seem to be a wierd feed issue cos I thought I had cured it ( by not knowing how ! ) and then it returned, it doesnt occur if the wiper multiplug is disconnected and it doesnt seem to be a wiper parking issue either. I will have another go in the next few days although pushing my arm into the back of the dash is making my arm look like Ive tried to bath a cat.


Bash

Tried a few more things, there doesnt appear to be a drop out relay as suggested by Tim so Ive been looking at the wiper delay box. First, if you disconnect it the slow and fast wipers still work as you would expect, what I didnt expect was that the wipers didnt automatically park when in this state, I thought that the park function was built into the motor so I need to look into this at some point. One aspect of the wiper delay box is that just like the steering column ignition wiring issues the wiring diagrams in the Excel manual are only partly right, or only right up to the multiplug connector to the module, after which the wires are a different colour. I havnt done a list on this because the module harness is so short that its not rocket science to figure out which is which. So I took the module off and had a look at it.


I then took it to pieces to have alook to see if there was anything obvious.


Clearly there is a relay inside the module.


So I did the obvious, pointing out that Im a mechanic and not an electrician, I cleaned the slightly dirty points, checked for any dry joints and then put it back together..... this being the sum total of my electronics expertise. So, did it cure it, did it eck. Back to the drawing board, or at a future date to take out the wiper motor an have a look, Im a bit busy at home at the moment so Im going to have to put up with it until I get the time. Bugger.

Bash

(ps, I have taken more pictures of the insides if anyones interested so let me know if you want to have alook )

It's probably just a "555" timer circuit triggering the relay. I can't see it affecting the self-parking function though.

Pete