Side light latch circuit - 2S

[miked]

During my recent rewiring I made a schematic sketch of the side light circuit. It may save some time if fault finding. I put it in my manual. Without testing the action of the switch, it is not that clear on the manual drawings.

Mike

[Sea Ranch]

Thanks for this, Mike. I have a Plus 2S (February 1970 build). The factory manual has a decent explanation, in words, of how it works, but pix always help.

My headlights work and the side lights come on with the headlights (and panel switch works as it should in each position). However, I can't get the sidelights to "latch" without the headlight switch pulled on. I've cleaned the relay, seems to be clicking and working, but I guess there's no power to the relay to keep it closed . . . ?

Randy

[miked]

Randy, from the drawing you can see that the latch leg has its own supply on C2. This must be favourite to check this is live at the relay C2 connection. If it is I would lift the wires off C1 and put a test lamp on the C1 relay contact and ground. Then get someone to hold your side light switch down on the dash. If it lights you prove your relay contact. C1 and C2 may be crossed. I drew it, as I recall, as per Lotus. Makes no odds as it is only a contact. Presume when you say head lamp switch you are talking about the vac air switch. The scheme I drew was for that type of system without a solenoid.

PS Your N/C contact for the up switch must be OK as you say the side lights come on but wont latch.

PS simple latch cicuit but a bit foxy the way it is wired in! Hence the diag' and colours.


Mike

[Breezehill]

Hi

Question on the side light relay. C2 should the feed to this be permanent?

Just in case I placed a live feed to C2 to make sure. However still switching the lights to on at the switch, the side lights come on but then go off when you release.

[miked]

Yes, as per the circuit diagram. Are you sure that the relay is operating. Can you hear or feel it click. If so, is the contact actually operating and making as it needs to so it can latch itself. I would test the relay independently to ensure the contact makes properly.
Note that if the relay does not operate and latch that the operation of the wedge switch will power the lights until you let go. See route to the light circuit through the closed down contact.
That would give your symptoms.

[miked]

Or!
If the relay is hunky dory!
The up contact on the wedge switch that switches them off is high resistance or total open circuit. Then the relay pulls in but can not latch due to the broken series path.
Try both tests.

[Breezehill]

Hi Mike

Did a few quick tests yesterday.

Relay is clicking, this is a new 6RA as I thought it may have been the relay.

Put a test light on C1 (red/green) which comes on when the switch is pressed down.

The same happens with W1 (blue) and C2 (brown/white)

[Breezehill]

On the front fuse box looking at the schematic seems to imply that the first fuse holder brown to white/black and the second fuse holder brown/white to purple have a jumper between them?

[miked]

I have no access to a Plus drawing at the moment due to move.
I see what you have tested and is promising but would show this on the test lamp if the relay contact was not giving a good circuit. Have you tested the relay contact C1 to C2 on ohms for continuity without any other connections. I would do this as without this closing you don't latch the circuit when you let go of the wedge switch from the pressed position.
Note, C2 should be live all the time without anything pressed. If not, you have a link missing

[Breezehill]

Hi Mike,

Just stepping back from it for a few days so I can get a clear head and clean start later in the week.

In the meantime sorted front fuse box sorted, they'd supplied the one for the +2S with Dynamo not the alternator. Both join fuse one and two but in different ways, the Dynamo version join at the control box while the alternator are physically linked under terminal 1 & 2 of the front fuse box.

[Breezehill]

Hi All,

Well having stepped away from this issue to review where I was at, I ended up having an operation on my hand so had to step away longer than planned.

However time not wasted and used the diagram provided by MikeD, many thanks and now we have the side lights correctly coming on and off using the new switch from Paul Matty.

The original issue was the sidelights permanently on when the battery reconnected. Using the MikeD diagram and working through a series of tests on the circuit it finally ended up with the sidelight micro switch. Disconnected this as part of the test and side light circuit works fine with the relay doing the correct latch operation.

So looks like micro switch may be faulty so will remove and bench test tomorrow.

[miked]

Great, glad the drawing helped.