Dipped beam not going off when lights are down

[JohnMorin]

Hi

I'm generally OK with car electrics especially the Elan S4. I have a problem at the moment though. Putting all the headlights back together with Cibie H4s:

Headlamp flasher OK
Dipped beam coming on OK
Main beam coming on OK
Main beam going off when headlamps are down OK
Dipped beam going off when headlamps are down NOT OK

I have to pull the red and black wire from the microswitch off the dipped beam relay to turn off dipped beam with the lights down. If I then reconnect it the lights stay off.

Microswitches are new and I have tested their function when installed. All terminals are soldered and tested end to end with a circuit tester. Relays were changed about 30 years ago, they are Lucas 6RA.

My suspicion is a sticking relay, what do others think?

Thanks

John

[Andy8421]

That's an interesting problem. Is it just the headlights you have changed? You haven't changed anything else?

If I recall correctly, there is a strange situation that can occur where the dipped beam headlight relay uses the main beam warning light as an earth and remains activated.

Couple of useful facts - a cold bulb (off) has a much lower resistance than a bulb that is on, and the current required to hold a relay on is much lower than the current required to switch it on in the first place.

Again from memory, in the situation that the dipped headlight is switched on, but the headlamp descends and the micro switch opens, there is an alternate path to earth for the dipped beam relay through the main beam relay coil and the main beam warning light to earth. Although the resistance along this path is too much to activate the dipped beam relay, it may be that enough current can pass to hold the dipped beam relay on.

Is it possible it has always done this and you haven't noticed?

[JohnMorin]

I'll try removing the main beam indicator light to see if that makes any difference

[Andy8421]

John,

Please come back and let us know how you get on. If I am right, a 'twopenny diode' will fix the problem, and I have a few theories about how the problem may have developed.

As anyone who has bothered to read any of my nonsense on this forum will know, I have a relatively low opinion of the electrical side of the Elan. This will be another issue to add to my rogue's gallery of problems.

Andy.

[miked]

Bang on Andy,
I have had the problem you describe on cars of my own and others and cured with a diode. A while ago now but traced to latching in through the warning light. Inheritant design fault.

[JohnMorin]

I had a thought that a diode would cure this if it is the main beam warning light. Can anyone suggest a suitable component, electronics is not my thing.

Thanks

John

[JohnMorin]

I've just pulled the main beam warning light from the back of the tach, it was glowing dimly. As soon as I removed the bulb the lights went out.

Well done Andy

[Andy8421]

I had a thought that a diode would cure this if it is the main beam warning light. Can anyone suggest a suitable component, electronics is not my thing.

Thanks

John

John,

The relay coil draws very little current, about 0.2A, but there is a risk that a voltage spike when the relay is switched off will fry a diode. A 1N4007 diode is a 'cheap as chips' 1A diode with a reasonable tolerance to reverse voltage spikes. A quick search on eBay has a pack of 10 for £2.28 - so 28p each (though you will have 9 spare). On low price electronic bits, its tough to buy components one by one, it just isn't worth the seller's time.

https://www.ebay.co.uk/itm/113823037967?_nkw=1n4004&itmmeta=01J5Z7XG24SK25KMRNS84Q7C3V&hash=item1a8061ba0f:g:S~IAAOSw8wheg4xQ&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKlUJnA34ScTiIkDtxUvUzUjYPVKnrtcWzzz%2BAnlLCwWUDo0fXuuWxryiFnXIYqr1H7kXsDGu3X%2Btl%2FOgtknF2smySt055Qe9M33SNkoouV0R6C7C77qxJ9tLqHDzSx%2BLiW8l05%2BPIOaV8GQXVyMjglg242ETPKYUaDkWO16IV8b9SItsCzyGa7Ao%2FyrXWSJ10IO8dWi5kRnrhzcPVdFE31HKqnQkW3aKrqy7pBiTbTMsD4bpkv%2BaxuJGurx6jmai8QdhRf4Tiw1AKLmmBECrALF%7Ctkp%3ABFBMloH2569k

Diodes are directional (that's the point) and the direction is marked by a silver or white band at one end. The diode would need to be fitted in series with the wire feeding the coil on the main beam relay, with the silver / white band at the relay end. Probably easiest to make up a little adaptor with a male spade at one end, the diode in the middle and a female spade at the other. Put a bit of heatshrink over it and you are done. You could pull the coil feed wire off the bottom of the relay, and put the adaptor between the feed wire and the relay.

Alternatively, if you don't want to mess around, should you find yourself in this situation with the dip relay latched, flipping the dip/main stalk on the steering column to 'main' should defeat the earth effect and cause the dip relay to de-energise, or simply turning the headlights off at the light switch should do it.

[Andy8421]

For what it's worth, a couple of thoughts on this problem.

It would appear to be an inherent design flaw, but easily overcome by switching the lights off or fiddling with the dip/main stalk. Perhaps very few people relied on the microswitches to turn the lights off, usually turning the lights off at the switch and pressing the vacuum valve at about the same time.

Those that did rely on the microswitches and had this problem probably put it down to idiosyncratic Lucas wiring - its not as if the rest of the car's wiring was 100% reliable either.

The microswitches were designed as courtesy light switches to be mounted in a door pillar where they were reasonably well protected from the elements. Not so in the Elan where they were exposed to the elements, and would often fail. Many Elans I have seen (and both I own at the time I bought them) had the microswitches removed or bypassed - and so avoided the problem.

[JohnMorin]

Andy,

would this do the trick

https://www.autoelectricsupplies.co.uk/p/universal-in-line-diode

Thanks

John

[Craven]

Change the warning light to a LED.

[elanner]

Is this it?

viewtopic.php?f=38&t=31227&start=

Nick