Lotus Elan

identifying actual relay terminals on wiring diagram -Sprint

PostPost by: bloodknock » Sat Jun 24, 2017 7:36 pm

Hello again fellow sufferers
can anyone help identify the actual relay terminals onto the Lotus sprint wiring diagram please?

regards
Bob
fullsizeoutput_1cbb.jpeg and
the actual relay terminals are not identified on the circuit diagram
I've got a deadline, at 73, I want to finish it before I die!
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PostPost by: fatboyoz » Sat Jun 24, 2017 11:51 pm

Hi Bob,
Here is a diagram showing connections for Lucas relays. Click on the small diagram, and it will enlarge.
https://www.autoelectricsupplies.co.uk/product/176

Our installation for Main and Dip beams is as follows:
U (power from control box to both high and low beam relays) C2.
UW and UR (power to headlamp units.UW to Main beam, UR to Dip beam) C1.
BR (to earth, for both relays, via headlamp microswitch) W1.
UN and UB (switching power from dip switch) W2.

The headlamp flasher relay is slightly different, in that the original relay had only one power input. This is from the light switch, on the dash, and is live whenever the light switch is in the OFF position and is connected to C2. Within the relay, there is a jumper from C2 to W2 and provides power for switching circuit. If you have to replace this relay, and you can't find an original relay with this internal jumper, you can rig up an external jumper from C2 to W2.
So, connections to the flasher relay as follows:
UY (from light switch on dash) C2.
WU (power out to High beam) C1.
YU (to earth via headlamp flasher unit and the other headlamp microswitch) W1.

A quick description of how the headlamp flasher circuit works:
Power to headlamp flasher relay from dash light switch when switch is in the OFF position. When the light pods are raised, the microswitch, on the pod, is closed and provides an earth for the headlamp flasher unit. The flasher unit flashes and provides an intermittent earth for the flasher relay, and the High beam flashes on and off. When the dash switch is selected away from Off (either side light or headlight) the flasher system is deactivated.
If you wish to flash your lights at someone, just raise the pods with the dash switch OFF.
If you wish to raise the pods without the headlights flashing, preselect the dash switch to either sidelights or headlights, and then raise the pods.

Hope this all makes sense.
Cheers,
Colin.


bloodknock wrote:Hello again fellow sufferers
can anyone help identify the actual relay terminals onto the Lotus sprint wiring diagram please?

regards
Bob
fullsizeoutput_1cbb.jpeg
'68 S4 DHC
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PostPost by: bloodknock » Sun Jun 25, 2017 8:14 am

Thats it Colin!
Many thanks for the excellent write up.
Onwards and upwards
Regards
Bob
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PostPost by: Andy8421 » Sun Jun 25, 2017 9:11 am

As anyone who has tried wiring up the 'flashing headlight' circuit as you have described with modern components (which I agree is correct according to the wiring diagram in the manual), it won't work. It is also questionable whether it is currently legal, though if it was legal in period it may still be legal now?

You correctly point out that a modern relay needs a jumper to power the coil, but the problem is the flasher unit. Two terminal flashers need the correct amount of current flowing through them to work properly. They have an internal bimetallic strip that is heated by the current flowing in the flasher circuit.

With a front and rear indicator bulb of 21W, a side repeater and internal tell-tale bulb, a normal Lucas style flasher circuit draws about 4 amps. A normal automotive relay will draw a fraction of this current, and a 'normal' Lucas style two terminal flasher wired up as you describe (and as is shown in the manual) won't flash as the bimetallic strip won't get hot enough.

Either Lotus used a special low coil resistance (and therefore higher current draw) relay, or they must have used a special low current flasher unit. A low resistance relay coil would lead to overheating, so either the circuit in the manual is wrong, the flasher never worked properly from the factory, or there is a special flasher unit.

- A modern 3 terminal flasher can be used as the time delay circuitry for the 'flash' is electronic and doesn't depend on circuit current, but it will need a bit of extra wiring.
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PostPost by: fatboyoz » Sun Jun 25, 2017 10:33 am

Hi Andy,
Sorry to disappoint you. I have exactly the setup as I have described, and as you rightly point out, it is as per the wiring diagram in the workshop manual. I have had the system up and running for the last seven years and it operates faultlessly. The two pronged flasher unit is not the original item, but was purchased from one of the Lotus parts suppliers. If I had to guess, I would say that it was purchased from Paul Matty. I used to regularly fly to the UK when I was flight crew, and always made a pilgrimage to PM, TTR, CN and QED to collect parts.
As for the legality of the system. Surely, if it was fitted from new and was legal at the time, it would still be legal today. A bit like seat belts etc. A moot point, perhaps, as one probably wouldn't use it in anger anyway!!!
I have a, normally open, tin box relay using the said jumper lead. Cannot comment on the flasher unit's resistance, other than to repeat that it was purchased from one of the suppliers.
I will say though,that the flasher unit is a squat item only about half the length of the normal indicator type flasher unit.
Cheers,
Colin.


quote="Andy8421"]As anyone who has tried wiring up the 'flashing headlight' circuit as you have described with modern components (which I agree is correct according to the wiring diagram in the manual), it won't work. It is also questionable whether it is currently legal, though if it was legal in period it may still be legal now?

You correctly point out that a modern relay needs a jumper to power the coil, but the problem is the flasher unit. Two terminal flashers need the correct amount of current flowing through them to work properly. They have an internal bimetallic strip that is heated by the current flowing in the flasher circuit.

With a front and rear indicator bulb of 21W, a side repeater and internal tell-tale bulb, a normal Lucas style flasher circuit draws about 4 amps. A normal automotive relay will draw a fraction of this current, and a 'normal' Lucas style two terminal flasher wired up as you describe (and as is shown in the manual) won't flash as the bimetallic strip won't get hot enough.

Either Lotus used a special low coil resistance (and therefore higher current draw) relay, or they must have used a special low current flasher unit. A low resistance relay coil would lead to overheating, so either the circuit in the manual is wrong, the flasher never worked properly from the factory, or there is a special flasher unit.

- A modern 3 terminal flasher can be used as the time delay circuitry for the 'flash' is electronic and doesn't depend on circuit current, but it will need a bit of extra wiring.[/quote]
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PostPost by: Craven » Sun Jun 25, 2017 10:59 am

The factory setup works perfectly well, Colin?s circuit description is as good as any and full marks to him for taking the time.
Lotus used a special relay for headlight flash. Part No 036 M 6022 referred in the manual.
This type of flasher unit has a separate heating coil so flash rate is independent of current flow drawn by the lamps.
Now with the use of LED flashers, the low current flasher unit used may be an alternative to the special relay.
Ron.
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PostPost by: pharriso » Sun Jun 25, 2017 12:26 pm

There's my wiring diagram in this thread, shows how the relays are physically connected, it's for Federal, but you'll get the idea - http://www.lotuselan.net/forums/lotus-electrical-f38/late-federal-fail-safe-headlight-wiring-t30133.html
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PostPost by: Craven » Sun Jun 25, 2017 2:47 pm

I?ve seen and commented on this circuit before, it?s not a good idea using a flasher unit designed for a load of 4 amps to be carrying 10.
Ron.
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