Lotus Elan

Warm Plus 2 Lights Toggle Switch

PostPost by: JohnP » Thu Aug 31, 2017 10:12 am

Hi All,

My Plus 2 has the Lucas Off/ Sidelights on/ Sidelights + Headlights On toggle switch with no relay (I believe).

I don't use headlights very often but noticed after running for 40 minutes or so the other night that the metal switch surround was quite hot to the touch.

1. is this normal bearing in mind current being passed?
2. If it is not I assume short term course of action is to replace the switch in case internal connections are poor and/or clean the external connectors. Is there any kind of compound I should use to improve the conductivity of the spade connectors on re-assembly?

Look forward to receiving your comments/ help.

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PostPost by: wotsisname » Thu Aug 31, 2017 2:10 pm

John, I'm definitely no expert , but here's my tuppence...
Mine is an early +2 & the wiring diagram shows a relay linked to the column switch, toggle switch & the headlamp microswitches .. i am assuming this is reducing the load on the switch.. but yet to fully comprehend the wiring diagram!
Running hot doesn't sound to good, but my car is not yet back on the road , so can't be sure what is reasonable.
I can't guarantee if the next bit is the right thing to do......but I figure the switch has to be dismantled or replaced otherwise.
I measured the resistance across all of my switches and some were significantly higher than others. I dropped the whole switch in to a derusting solution (deoxy-C, which I believe is Citric acid) for a short while [don't leave it too long as it will eat into the copper, I think I went for less than an hour] , then soaked them in a jar of WD-40 and allowed to dry for a while in a bundle of tissue... The resistance was significantly lowered (to little/no more than the cables from the multimeter, set at most sensitive). I've yet to test the effectiveness for real but I'm hopeful !!
1968 Elan plus 2 - project
2007 Elise S2 [modified with a Hethel 70th sticker (yellow)]
2000 Elise S1 - Sold
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PostPost by: MarkDa » Thu Aug 31, 2017 4:45 pm

Yes, headlights should go through a relay.
Not doing so runs the risk of a classic lotus dashboard fire.
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PostPost by: bob_rich » Thu Aug 31, 2017 6:01 pm


I can't comment on the relay issue as my +2S (Later 1974 model) does not use a toggle switch but uses a combined rotary and pull switch for the side and headlamps and this was used directly and not with a relay. Whether this is wise is a moot point but it seems to be OK

The spade connectors can overtime show signs the contact grip relaxing and the resistance rising. I have seen more problems over the years with poor spade (and bullit) connectors that I have switch contacts.

a test meter is not the best way to check very low resistances as , as another post says, the test leads may be a lot higher resistance that the contact resistance value

the best way I have found is to pass a know current through the part being tested and use the test meter to measure the voltage drops. Most test meters can measure low voltage very well so an idea of the resistance can
be obtained quite accurately.

The other factor is that generally if a contact gets hot its resistance will rise and this means more loss more heat ....... and so on leading to some serious damage

Hope this helps best of luck

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PostPost by: mbell » Thu Aug 31, 2017 6:23 pm

The head lights are ~55W a piece, so there ~110W for both lights. That somewhere in the 8 to 9A range which a fairly high load. So I wouldn't be be surprised or too concerned about the switch feeling a touch warm but feeling hot would concern me.

As pointed out the heat will be coming from a poor connection, which could be the actual switch internal connections or wiring connections. So cleaning the extenal connections would be sensible, especially as switch is reasonably accessible from drivers foot well.

But real fix is to fit some relay in the nose of the car and remove the high current flow from the switch and dash wiring. You should be able to find a suitable power source in the nose or use the alternator (with inline fuse). You should also do it for the full beam bulbs as well as dipped.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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