Lotus Elan and Lotus Elan Plus 2 Forums

I am completely re-wiring a 1967 UK version S3 Elan. I have the option of using up to 11 relays with my current (no pun intended) equipment. Choices are:

Headlights - main
Headlights - dipped
Left window up
Left window down
Right window up
Right window down
Horn
Electric radiator fan
Heater fan

Any other suggestions?

Thanks,

One for the accessories and one for the ignition to relieve the stress on the ignition switch ?

John

Wiper motor draws significant current, particularly with a dry screen. Two speed motor / self parking will need some thought though to use relays.

The solenoid used for pre engaged / geared starters can draw significant current if you have one fitted.

john.p.clegg wrote:One for the accessories and one for the ignition to relieve the stress on the ignition switch ?

John

I've been starting to think about custom loom for my plus 2. I agree with John on this, I was planning a couple of big relays for switching the ignition circuits on.

Basically any device that pulls a significant current would go through a relay.

My first step with be to spread sheet every electrical device in the car to map out wire colors, location, current, power source. From that I can identify relay and fuse requirements.

Thanks for the replies.

The draw from an ignition circuit, especially an electronic (e.g. Pertonix) should not be much. Although, with an extra relay available it would not be a bad idea.

Same for a gear-reduction starter. The wire from the start switch merely triggers the solenoid, acting as a type of relay itself. At least that's always been my understanding. Someone please correct me if I am wrong.

A rather simplistic approach but if it has a thick wire, consider a relay!

Mike

A relay for ignition circuit is good idea to separate the pertronix power line from the coil supply for the tach. I also run elec fuel pump, rev limiter, alternator line of that circuit via the relay. None of it is that high power but relay is good for extra reasons:
- relay is triggered via a fuel cut of switch so crash will kill fuel supply and engine
- removal of the relay gives good security measure
- the relay will trigger with a voltage lower than 12v, so even if isn't switch isn't great you get more reliable operation
- relay is less likely to get a bad connection and much easier to fix/replace

I am not sure what the current pull for the solenoid is but I'd expect it to be quite noticeable, amp or so, as quite a heavy device. So worth considering a relay but given amount of time it is active it might just be a little bit of over kill but a lot of the above probably applies...

Gear reduction starter research shows use of a 12 - 14 gauge wire recommended for the starter switch with typical amp draw maxing out around 15 (which is max for a 14 gauge wire at normal temps), depending on length of wire. Not a bad idea to use a relay for the starter and 12 gauge wire from the relay..

Thanks,

relays are to protect cheap switches[in new cars] or enable automation

they add failure points and will become impossible to decipher years from now

How many switches have you replaced?

I have replaced my microswitches, kill switch....that's it

replaced horn and low beam relays

IF you have 2 fuse wiring, it could use more fuses, the last +2 had 4 which I think is fine.

Increasing wire size and ground size is really all that is needed.

adding complexity is asking for trouble.

fattogatto wrote:I am completely re-wiring a 1967 UK version S3 Elan. I have the option of using up to 11 relays with my current (no pun intended) equipment. Choices are:

Headlights - main
Headlights - dipped
Left window up
Left window down
Right window up
Right window down
Horn
Electric radiator fan
Heater fan

Any other suggestions?

Thanks,

Charlie,
If you Elan is a Coupe, another circuit that would benefit from a relay would be the rear window defogger.

Regards,
Dan

fattogatto wrote:Thanks for the replies.

The draw from an ignition circuit, especially an electronic (e.g. Pertonix) should not be much. Although, with an extra relay available it would not be a bad idea.

Same for a gear-reduction starter. The wire from the start switch merely triggers the solenoid, acting as a type of relay itself. At least that's always been my understanding. Someone please correct me if I am wrong.

The solenoid on my high-torque starter pulls 35A. According to the Bosch Automotive Handbook, this type of starter/solenoid will pull over 30A so a relay seems a good idea.

Galwaylotus wrote:

fattogatto wrote:The solenoid on my high-torque starter pulls 35A. According to the Bosch Automotive Handbook, this type of starter/solenoid will pull over 30A so a relay seems a good idea.

Aye, but you need a high-current contacts relay for that. Which is exactly what the old starter solenoid is. It's only a relay in any case.

I know that but I didn't have one and I did have a 40A continuous relay so I've used that instead.