Sudden blackout on a country lane!

[JonB]

Hi

First problem detected with my +2.

Driving in the dark with the headlights on. Suddenly I hear a click (seems to come from the light switch) and the lights go out and drop down. Dashboard lights too. Switch hasn't moved, is still in "main lights on" position. Then they come back on and pop up (with another click). Closing the valve (by pushing the switch in) and opening it again doesn't help - the headlights would come back on but only after a random period of time varying between 10 seconds and a minute.

This happened repeatedly at random intervals. Very dodgy on a twisty backroad with no street lights. Fortunately, not quite dark!

What might be the problem? Vacuum switch? If so, how come it's killing the sidelights / dash lights too? The sidelight switch seems to be reliable on its own.

Other thing I noticed - when the lights pop up, they pause at about 80% for a second or so, then come up fully. They also come up of their own accord when it's cold (according to the PO). Most odd.

Any thoughts?

[JonB]

Hmm, found this on another thread:

The Lucas pull and twist headlight switch is used in conjunction with a solenoid operated valve. The Solenoid operated valve switches the vacuum (ie it allows the vacuum pod to communicate to atmosphere=lights up for fail safe or communicate with the vaccum reservoir=lights down for fail safe). Note, the solenoid operated valve should have a filter on the porting to atmosphere to prevent dirt etc getting into vaccum system then non return valve.

If it has a solenoid operated vacuum valve there is the most likely culprit - or rather its wiring. Where would I find the solenoid?

I read of a "failsafe" mode, how is that implemented? Mine obviously doesn't have it!

[types26/36]

lotus-twincam-f39/thermal-cutout-t13267.html

[JonB]

Hey Brian, thanks very much for the link!

My god, what stupidity is this? A "thermal cutout" connected to the lighting circuit? Very bad indeed.

So - choices would seem to be:

• Don't drive at night!
• Look for bad connections / earths and make good.
• Replace the cut out with an inline 10A fuse.
• Go full-on relay for the main lights (and fit the 10A fuse inline).

I think I'm inclined to fit relays and leave the cur out as-is. All work can be done under the bonnet and it should (famous last words) be reasonably accessible. Should I look to fit period correct Lucas 6RA relays or does it not matter? The car is mostly unmolested save the Spyder chassis.

[alan.barker]

What model and year is it just to make things clear. +2, +2S or +2S130.
They are all different
Alan

[prezoom]

Check the main power connection to the thermal switch. I also had some similar lighting issues, and found the spade connector to the switch has lost its tension, and was making infrequent contact. The connection can get quite hot via the high resistance connection, so be careful when feeling around. Have the burn mark on my thumb as evidence. Replace, or tighten the spade connector and all should be good.

[billwill]

Having a cutout there is kinda mad!

About the only safe-ish way to do that would be to have separate cutouts for left & right headlamps so you only lose half your lighting.

But that would involve more wires.

I had the main-beam fuse fail once, but fortunately the dipped beam fuse was OK.

[Robbie693]

http://www.lotuselan.net/forums/lotus-twincam-f39/thermal-cutout-t13267.html

I had completely forgotten that post! Reading it again I realise I never finished it up by reporting what I did to fix it.

I used the inline fuse to loop out the thermal cut-out as a temporary fix and eventually installed relays with inline fuses and then re-instated the thermal cut-out. I used modern relays hidden in the nose with waterproof flying sockets and fuse holders.

As to the reason for the problem, the only thing I could find was the 60/55w halogen bulbs were possibly taxing the system slightly too much for the thermal cutout to tolerate, possibly because it was old and worn...

Robbie

[alan.barker]

Sorry to repeat but what +2 model do you have, it makes a big difference
Alan

[JonB]

I've updated my signature, see below.

[alan.barker]

I had a 1973 +2S130 and i replaced the Solenoid which was fitted to the inner wing just before the Rad. On the exhaust side. The Solenoid have a "Viton" valve and worked fantastic.
If the headlamp dip switch is in mainbeam position (up) you can pull it back and it will operate the Solenoid to flash the Headlamps.
The photo is the new Solenoid Valve i fitted.
Alan

[vincereynard]

The failsafe refers to the method of raising / lowering the lights. Early cars used the spring to pull them down - hence a vacuum failure would see them close. Later the spring raised the pods - fail safe. Hence with your light failure they simply folded away as commanded by a switched off situation.

The thermal switch is decidedly flaky but is there to prevent a straight electrical short, (fire behind the dash?), as the light circuit is connected directly to the battery, via the starter solenoid.

A serious retrograde step with the 130 was the replacement of the original (S) 12 fuse with the central dash 4 fuse. Presumably for cost.

What I have found is there are no short methods with a Lotus. Chuck the thermal away, replace with a 10 amp inline fuse and rewire, (with decent sized cables), including relays for both circuits. Bright, reliable lights.

Also this is good kit, despite the vendors -

http://www.spydercars.co.uk/electricy-h ... lan-elan-2

Obviously you can DIY much cheaper, there are loads of threads showing how.

[alan.barker]

Imho it is bad contact to the Solenoid Valve just before the Rad on inner wing. Or Switch to power the Solenoid Valve on the dash.
Try to power the Solenoid Valve direct which will bring headlamps up and light them. If it operates then the fault is at the dashboard switch.
Alan

[JonB]

I can DIY it.

Have ordered two relays (one for main, one for dip) with inbuilt 30A fuses, plus some 20A cable and some spade connectors. I'll run a 12v feed direct from the starter solenoid's battery connection to the relay switch, with the other side going straight to the main on the bulbs. Then feed the old main +ve connections to each relay coil. Same for the dip circuit. Lay in new earth as well, and it should be sorted.

As to access, I assume you go through the front grille? Can't see any other way to get in there.

[vincereynard]

30A fuse is a bit excessive just for head / dip lamps. Ohms Law? A = W/V

Taking the bonnet off helps access.

I've also considered getting a pair of good LED bulbs for the spots. Low wattage so they can be used as running light / auxiliaries if the main lights fail. I bought a pair of cheapos from the "Far East" and they were useless.

There are some big "earth" connections at the top of the front suspension towers on my Spyder chassis.
(Inside the engine bay.)