Air horn relay

[Mrozik]

HELP

I'm in the process of restoring my 1968 Elan +2. I just replaced the air horns with new. Problem is that when I took off the older relay I didn't mark the wire positions and no matter what I tried I just can't get the horns to work (PS they do). Here's photos of the two relays. The older one has an extra pin. There are 3 wires - Light green Brown/white - Brown/black

Can some one help?

Many thanks
John

[JonB]

First off, the "older relay" isn't an original part.

There should be a diagram on the relay body showing you what each pin does. For the four pin relay it is standard:

4 pin automotive relay wiring

So you need to match the coloured wires to the corresponding tabs on your relay. Problem is, your wires aren't the standard colours, which are Purple - the +12v fused supply; Purple/Black - the switched 12v from the horn button and Purple/Yellow - the power to the horn +ve connector. Other side of the horn is grounded.

You'll need a test tool like a bulb with a couple of wires. Connect one of the bulb's wires to ground. Now touch the other end to each of your fuse connectors to work out which is which

In the standard colour scheme:-
The one that always lights the bulb is the PURPLE wire.
The one that lights the bulb only when the horn button is pressed is the PURPLE/BLACK wire
The other wire is connected to the horn - PURPLE/YELLOW

So now, we can see where to connect these to the relay (using the standard colour scheme):

PURPLE - pin 30
PURPLE/BLACK - pin 86
PURPLE/YELLOW - pin 87

plus

GROUND (black) - pin 85

[JonB]

I've had a look at the wiring diagram and it is likely that:

LIGHT GREEN wire is the 12v feed to the horn.
BROWN/WHITE is the fused power feed
BROWN/BLACK is the switched power feed from the horn button

[Mrozik]

Many thanks I'll try it out first thing tomorrow
Cheers
John

[Matt Elan]

Having just done the job on mine the relay should have a main power in, possibly a second power in which is ofter slaved to the other power in, a power out which goes to the horns, and an earth which goes to earth through the horn push. So when the horn is pushed, the low power feed switches the relay and the high power feed is connected to the horn feed.
To test which is which use a test light - the 'power in' wire is permanently 12v, you should have identified the feed to the horns having wired them in, then find the horn earth by checking each wire for continuity to earth when the horn button is pushed. Then its just a case of putting the right wires on the right connector.
The wiring diagram for the horns should show the correct spades on the relay.
The original relay had:
The earth via switch terminal is marked FUL with a PB (Purple and black) wire that goes to earth via the horn button
The power to the horn terminal is marked TR and had two PY (Purple and Yellow) wires - one going to the horn compressor and the other to the anti theft switch,
The main power feed is BATT, and has two P (purple) wires going from it to the fuse box (live feed) and the engine bay lights which were switched elsewhere.
So your wires are not standard which doesn't make the job any easier!

HTHs
Matt

[JonB]

Matt you’re right the horn switch connects the relay solenoid to earth. My description supposes the live side of the solenoid is switched by the horn, which is wrong. Oops.

[Mrozik]

Many thanks for everybodies help - the horns are working now.

It turned out that that I must be a bit colour blind, the wire colours were in fact purple/white or black but the main problem was that there was no secondary power through the purple/black wire so I had to find the reason which I eventually managed.

Again thanks
John

[Mrozik]

I came across another smaller problem regarding the head light flasher relay located next the horn relay. If I connect the two wires it starts flashing. My gut feeling is that the relay is faulty as it also get hot but appreciate suggestions. Thanks John

[Matt Elan]

Relays have to have at least three wires - so you are missing one. It also sounds like you've got the wires mixed up but I cant quite think what would cause th 'headlamps to flash' unless you are connecting the power to the headlamps wire directly to the main power feed wire.

[Bigbaldybloke]

Maybe a problem with the headlamp pod micro switch, they aren't the most reliable things!

I think on the early cars if the ignition is on, the headlamp pods are up but the headlamps are not switched on then they start flashing. The idea being if you wanted to flash your lights all you needed to do was pul the vacuum switch and the lights came up flashing.

Just as an aside, you can get metal body relays that use the metal mounting tab as the earth, obviously not much good on a fibreglass bodied car!

[Mrozik]

Many thanks - I think the logic makes sense
John

[Mrozik]

This is the wiring diagram I have
John

[Craven]

What the diagram doesn’t indicate is that headlight micro switch is mounted on one pod and the flasher micro switch on the other.
FWIW

[Bigbaldybloke]

My micro switches were both on the left hand pod, but it’s a very early Plus 2 so maybe later versions changed? Wouldn’t surprise me with Lotus!

[Craven]

My micro switches were both on the left hand pod, but it’s a very early Plus 2 so maybe later versions changed? Wouldn’t surprise me with Lotus!

My mistake I was referring to a 2 seat Elan, I think there were quite a few changes on later +2’s including micro a switch on vacuum pull switch. I keep well clear of +2 electrics, I think Lotus lost the plot somewhere along the way.