Lotus Elan

Small l.e.d. lamp in dashboard fixing screw

PostPost by: ericbushby » Tue Aug 08, 2017 2:23 pm

Hello all, can you help.
Some time ago someone posted an idea about fitting an extra dashboard light inconspicuously by drilling one of the large chrome dashboard fixing screws and fitting a small led inside.
I was discussing this with a friend recently and now I cannot find the topic.
I have searched for it and failed.
If you are out there can you prompt me, or if anyone else knows where it is please give me a clue.
Eric in Burnley
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PostPost by: gherlt » Tue Aug 08, 2017 8:59 pm

1964 S1 (engine ready, awainting body paint)
1967 S3 DHC (now adjusted by Brian Buckland, totally calm idle)
1969 S4 FHC (final interior stuff)
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PostPost by: ericbushby » Tue Aug 08, 2017 10:40 pm

That`s the one! Thankyou.
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PostPost by: john.p.clegg » Wed Aug 09, 2017 5:35 am

Eric
Looking at that , I'd use some thin wires to extend the LED leads and fit the dropper resistor further down the line , outside the screw body , you've also got the problem of screwing it into the dash with wires protruding , unless you make it a push fit after fitting , keep us updated.

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PostPost by: 7skypilot » Thu Aug 10, 2017 6:50 pm

I've LED warning lights located in the cross-headed dashboard fixing screws for: radiator fan, rear rain light (located in the 'spare' reversing light), oil pressure (between rev and speedo) and for a tiny pair of auxiliary lights located in the grill. The car is an S4 Coupe

All are 3mm LED's of various outputs and colours. Oil P is a very bright 3000mcd (IIRC) and stands out even in bright sun. The oil pressure switch is set (by Think Automotive) at 15 psi and will illuminate at a slow idle with a hot engine. Fan is green, rain light is blue, and aux lights warning light is a (weaker) red. The aux lights are powered by a latching relay independently of ignition switch position. I wanted a completely separate light system that I could rely on when all else has failed. It's also useful as a quick 'flasher'. Switches for aux and rain lights are out of sight below the dash, but reasonably easy to use.

The bolts were drilled 3mm and followed a small outer rebate of 3.2mm allows the LED to seat neatly in the 'cross'. The wiring is a little delicate with not a lot of room available to solder and insulate the extension wires to the LED. I've found it's better to mount the necessary resistor well away from the bolt to avoid complications due to the size of the resistor compromising the 3mm bore within the body of the bolt.

The result is just about invisible, and gives me good, bright warning lights.

All lights on the car are LED, except the ign light, giving about a 70% decrease in load. H4 headlights, whilst not for purists, are excellent unless scrutineers are very picky.

Hope this helps.
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PostPost by: ericbushby » Thu Aug 10, 2017 7:16 pm

Thankyou, that is interesting and encouraging. I have ordered some 3mm leds which have the resistor built in for 12 volts. With such a small resistor I wonder if they will be bright enough. They are only 18 pence each, so they are going to be given a chance. Work in progress !
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PostPost by: ericbushby » Sat Aug 26, 2017 2:01 pm

dscf0426.jpg and
dscf0426.jpg and
Progress report as promised.
I have fitted one of these LED lamps as suggested.
The LED is from CPC. order code SC14319. Manufacturers part No. L 934 GD-12v. They are ?1.80 for 10 and available in red and green.
No external resistor is required.
I used 16/0.2 wire which has an outside diameter of 1.5mm
I squeezed the LED legs in a little to gain 0.5mm insulation space and cut away some of the wire strands to reduce the bulk of the soldered joint. I could have used thinner wire but judged it to be too delicate for under dash wiring.
The small heat shrink sleeving is 2mm and the outside cover sleeving is 3mm.
I drilled the screw 3.8mm to make the lamp a firm slide fit. At the head end of the hole it is 2.8mm for the last 1mm so that the lamp cannot protrude.
The lamp shown is to indicate that the fan is running and is close to the temperature gauge. The fan switch is under the dash, bracketed off the same screw, so that the whole system is grouped close together.
Eric in Burnley
1967 S3SE DHC
No holes drilled anywhere and can be removed entirely in a few minutes.
PS
I cannot see how I got the first picture twice and the last line appeared in the wrong place but it has taken me so long to get this far that I dare not try to improve it !!
Attachments
dscf0420.jpg and
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PostPost by: john.p.clegg » Sat Aug 26, 2017 3:11 pm

Eric

Nice one...

John :wink:
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PostPost by: 1owner69Elan » Sat Aug 26, 2017 11:33 pm

I also followed this same path of putting an LED in a dash screw as a warning light.

In my case I wanted to have an indication of my oil temperature. Having just installed a new dash it was too late to add a hole for an oil temperature gauge. In any event, an idiot light that indicated cold, warm, and hot would do the trick as well.

I installed a programmable Autometer Oil temperature gauge in the glove compartment. Then used that to drive a tri -color LED (Red-Green-Blue) as follows:

Blue: Cold, wait before romping on the car
Green: Warm, good to go
Red: Hot, reaching breakdown temps. (highly unlikely).

I drilled the dash screw as much as made sense given that I had 4 leads (R,G,B, cathode) to feed through. To make this work I lengthened the LED leads with the same small gauge lead wire before attaching the larger gauge (22) wire for hookup to resistors and the gauge/relay wiring). Used small shrink wrap to allow all four leads to fit inside the screw as per the picture. Relays were used to create the logic paths of when each color was triggered.

The indicator works great (don't know about Red - don't ever expect to reach that regime). But, the light starts out blue and then changes to green as per set limits.

I added additional resistance to the green lead so that in normal driving the light would be unobtrusive. Blue however is bright with the selected resistor, but it is only on until warm.

A very neat solution not involving drilling any holes in my pristine dash. I had been all set to add a dash light similar to the parking/brakes/hazard lights requiring the drilling of a 1/2 inch hole, somewhere. But thanks to the fortuitous timing of another member asking about the LED dash lights this alternative solution was perfect.

Only thing now is that it appears that the oil temp, as measured at the sump generally shows a pretty cool 140-145 F (62 C). I believe the oil cooler sandwich is set for 165 F. Also, pretty cool. Meanwhile the water temp is typically around 175 F (80 c).

I am initially (haven't put many miles on the car) concluding that :

1. The sump temperature at the plug sensor is probably 20 degrees F cooler than at the filter head.
2. Also that the water temp and the oil temp, after steady state is reached, are consistent if one assumes that the sump temp takeoff is 20-25 deg cooler than measured at the oil pump.
2. But, concerned that these indicated cool temperatures, if valid, are not necessarily good for the engine?

Ironic, because until the rebuild of my car I was always plagued with running hot. Now, I have to idle in traffic, without moving, in warm weather for 10 minutes before either the water or oil temperature approaches 200 F (93 C). More than ample cooling capacity even with a high output engine! Maybe in full race mode (not my case) the cooling capacity would make more sense. On the other hand today it is 107 deg F (42 C) and I would probably be thankful. But too hot today to even venture out and drive a drophead anyway !

img_8094.jpg and
Lengthened LED leads and shrink wrapped


img_8095.jpg and
Fed through the dash screw


img_8213.jpg and
Gauge in glove box


img_8214.jpg and
Green indicator (low light level)


img_8100.jpg and
'69 Elan S4 SE
Street 181 BHP
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PostPost by: Chancer » Sun Aug 27, 2017 4:43 pm

Your Leds with a built in series resistor will probably also have reverse polarity protection, if they havn't then its good practice to use a series diode to prevent them from being blown if ever the battery is connected the wrong way round, unlikely but it also gives transient protection.

Now that info is 25 years out of date and the world has probably moved on some, back then I was soldering up Leds, diodes and series r?sistors costing pennies then and selling the resulting product as a vehicle anti-theft d?terrent, I had worked out a simple way of wiring them with two 12 volt feeds and no negative so that they would flash automatically when the ignition key was removed like a real car alarm, advertised in the Expand & Fart only ?14.99 to you sir including postage :D

The world has moved on a bit from then, life is tougher for the Chancers!!!
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PostPost by: ericbushby » Sun Aug 27, 2017 5:41 pm

Chancer, yes they are protected against being carelessly connected the wrong way round, but I will not tell you how I know. But I now know that the short leg is negative.
Eric
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PostPost by: ericbushby » Sun Aug 27, 2017 7:03 pm

1 owner,
You see, that's the thing with you Americans. You always have to take it too far.
Here`s me, I only want a lamp to tell me I have left something on, and then you go and put traffic lights in !!
Seriously though, I am impressed that you managed to get all that in there. I had enough difficulty organising it to get a simple led with only two wires in. Respect!
On mine the lamp doesn`t project into the screw slot, in fact you could still use the screwdriver on it.
Eric in Burnley
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PostPost by: 1owner69Elan » Sun Aug 27, 2017 7:16 pm

Yes, too much time on my hands. Got involved in figuring how to switch the lights dependent on temperature as a challenge. Overkill. For sure.

All this was motivated by having the oil cooler and wondering if it did anything or was working properly. Originally I wasn't going to include an oil cooler but the engine builder recommended it after the lengths he had gone to with the engine.

Once the newness wears off, probably not pay much attention to the light. And drive as I always have done: let the car warm up, watch oil pressure, etc.
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