Help with halogens please

[Carledo]

As to putting a relay in the supplies from the ignition switch, I'm not sure what your suggestion is Steve.............

Graham

Basically, as you thought, i'm putting a 3rd relay in series with the main and dip relays this will have a nice chunky permanent live to the 30 and 2 from the 87 to the 30s of the headlight relays. then it can be switched from the ignition live from the fusebox or the pink and white ignition auxilliary, (radio) you choice! at very little cost to the system.

Yes if it fails (IF!) you won't have any headlights. I usually carry a spare or two out of old habit, in much the same way as I used to carry a spare Accusark EI kit, if I have one, i'll never need it! So far, i haven't needed it! It's not as if relays are prohibitively expensive!

Steve

[GrahamFountain]

If I can't modify the master switch and I want the headlights switched off by the ignition but the sidelights left on, I do need another relay or two controlled by the radio output. Either one between the master and stalk switches, or one in the common feed to the two existing relays, i.e. before their individual fuses; or two more relays, one after each of those fuses.

Graham

[Carledo]

If I can't modify the master switch and I want the headlights switched off by the ignition but the sidelights left on, I do need another relay or two controlled by the radio output. Either one between the master and stalk switches, or one in the common feed to the two existing relays, i.e. before their individual fuses; or two more relays, one after each of those fuses.

Graham

I don't bother to fuse the relays, the fuse needs to be so high rated as to be almost redundant, the 35 amp fuse recommended in Tony's diagram is a bit marginal for a quad halogen main beam draw of 280w (23+a if my sums are right) as, though 35a is the blow rate, the continuous load rating is only 17a. By MY reckoning you'd need a 50a fuse to protect this circuit properly. And the wire would probably melt before it blew!

Instead I fuse the individual headlights AFTER the relays, 4 fuses in the modern fashion covering L/dip, R/dip, L/main and R/main For this function I use the combined relay and 3 fuse holder sold by Car Builder Solutions (among others) This allows you to use lower rated fuses and means a fuse blowing only loses a single lamp. (or 2 on 1 side for main beam) Also makes fault finding easier.

The 3rd fuseholder comes in handy as a feed to a rear fog light switch from the dip relay. And you could use the 3rd main beam one as a supply for a spotlight switch.

I have to admit, I don't have a fancy degree, just 50 years of experience with what works. Some of it learned the hard way! I'm a keen student of how manufacturers build their looms and the economies they practice to get the most use out of the least wire. I built my first working full car loom at 19 ( a 3 litre V6 powered 1961 Ford Consul with a 10 dial custom dash) and have been practicing ever since.

Steve

[GrahamFountain]

Well I am using 50's in the mains and dips in what are supposed to be PTFE holders crimped onto high current capacity (I forget what) wires. And, other than some of the cheap fuses came apart, had no problems.

I've also come to the conclusion the best place (for me) to put auxiliary relays is one each on the control side of the main ones, with their power taken from the ignition radio output and the their controls from the output from the lighting stalk. That way, their coils are only energized when the relevant lights are turned on, and not turned on each time the engine starts (at least twice). Also, neither is a single point of failure for all the lights.

As to "fancy degrees". In terms of engineering, I think of them as just a shortcut ladder into the profession. The graduates that come into our place mostly start from not being able to find their arse with both hands and a map. And most still slither down a snake into management. The other day I had one of them barely necessary evils ask me if 400Kg was 4 or 40 tons! No, I mean really, that was a genuine question from a manger in R&D! Some think he's a pain in the neck, but I have a lower opinion than that.

Graham

[Carledo]

Well I am using 50's in the mains and dips in what are supposed to be PTFE holders crimped onto high current capacity (I forget what) wires. And, other than some of the cheap fuses came apart, had no problems.

................. That way, their coils are only energized when the relevant lights are turned on, and not turned on each time the engine starts (at least twice). Also, neither is a single point of failure for the lights.

Graham

You don't really need a 50a fuse for dip relay, the load is much lower than main beam at 110w (a tad over 9a)

TBH, I hadn't considered that an ignition powered relay would have its coils running all the time the engine is, though for my multifunction ignition relay for the engine and trans this is a necessary evil. Maybe i'll just leave the headlights as they are and fit a buzzer! That's using the KISS principal!

I should have known better really, I incorporated a relay to run the central locking before I had any of it in place (or even in the design stage) it seemed like a clever thing to do at the time, but I switched it from a fused permanent live and then wondered why the (new and large) battery went flat in a week if left connected! (gif of Homer Simpson going "D'oh" here if I had one) It's now been repurposed to run the electric boot release and only gets energised when a button is depressed in car or on the remote! The fused permanent live that energised it is now to the 30s of the 2 Volvo relays for the CL where it should be!

I share your disdain for most "graduates", i've run into the same thing over the years with newly qualified MVTs, they tend to know very little, especially if they've served their time at a single make franchise!

Steve

[GrahamFountain]

Here's the diagram for what I was thinking. But looking at it, I might apply the KISG principle - equivalent to Keep It Simple Steve.

And the advantage of 50A in both circuits is I don't have to remember which colour wire feeds which lights.

What failure case might cause the dips to draw more than say 15A but less than 50, what's their likelihoods, and what are the potential consequences? Oh God no - doing an FFA on the car already.

Graham

[GrahamFountain]

But keeping it simple or not, this alternative has the disadvantage that coils of the auxiliary relays would stay in circuit all the time the ignition's on. But the advantage that they wouldn't draw any current if I left the lights on with the ignition off. Not that it's much. A six and two threes perhaps.

There might be an alternative with a single NPN transistor and resistor instead of the auxiliary relay. An emitter follower would work as an AND gate in this special case where logic 0 is open circuit (the base-collector junction wouldn't saturate when the base input's at logic 1, i.e. 12V, and the collector input's at logic 0, i.e. OC not grounded). That should draw near to nothing with either lights off or ignition off. I'd need to know the minimum and maximum values for DC resistance of the relay coil and the minimum coil switching voltage to spec the transistor and base resistor.

But that's adding the complication of a PCB.

Graham

[Carledo]

Here's the diagram for what I was thinking. But looking at it, I might apply the KISG principle - equivalent to Keep It Simple Steve.

And the advantage of 50A in both circuits is I don't have to remember which colour wire feeds which lights.

What failure case might cause the dips to draw more than say 15A but less than 50, what's their likelihoods, and what are the potential consequences? Oh God no - doing an FFA on the car already.

Graham

Well, I can find no fault with your circuitry or logic.

A simple tippexed M and D on the relays identifies them well enough in my book! Lucas colour codes are indelibly engraved on my memory as a backup, but i've allowed for the possibility that someone else may one day need to work on the car.

To that end, i'm producing an "owners handbook" for the Dolomega with all the mods listed with part numbers for service items like spark plugs, oil and fuel filters, oil types, brake pads, fanbelt etc and circuit diagrams for the modified wiring, fuse box diagrams with allocated functions and so on. I've changed SO much away from standard that, even now, its hard to remember it all! This may even help ME as I get older and the memory fades even more!

What failure case? A blown bulb is the most likely I would have thought, this often produces a big enough surge to blow a fuse on a normal modern (typically 10a for a single dip or main. Though I use 2 x 20s on quad mains)

I did give some thought to going completely modern with the headlight layout and using constant single filament dips with the inners added on when main beam engaged. There are several cars with a massive and rather complex single relay that does all that for you, but, in the end, KISS triumphed and I left well enough alone!

Steve

[soe8m]

What I used to do was fitting two relays inside the column cover to unload the dim/dip switch.

The original brown light main feed supplied those relays. A thinner take off back to the main light switch feeding the courtesy lights and the relay coils. An ignition feed light system only needed a white take off or pink/white take off to the main light switch. These can handle the courtesy lights and relay coils easily. It's two relays taking over the dim/dip using the existing wiring.

Jeroen.

[GrahamFountain]

What failure case? A blown bulb is the most likely I would have thought, this often produces a big enough surge to blow a fuse on a normal modern (typically 10a for a single dip or main. Though I use 2 x 20s on quad mains)

Steve
[/quote]

I meant that I can't see any failure cases where using a 50 Amp fuse instead of a 15 Amp one adds any significant risk. But I didn't put it that way cos I might be wrong.

Graham

[GrahamFountain]

What I used to do was fitting two relays inside the column cover to unload the dim/dip switch.

The original brown light main feed supplied those relays. A thinner take off back to the main light switch feeding the courtesy lights and the relay coils. An ignition feed light system only needed a white take off or pink/white take off to the main light switch. These can handle the courtesy lights and relay coils easily. It's two relays taking over the dim/dip using the existing wiring.

Jeroen.

I think that's functionally the same as what I have at the moment, except the relays are under the dash, and there are fuses in the feeds doing the job of the brown wire. I used the same colours as the feeds to the lights for them: I know that's not standard, but it allows for their identification with a memory that's as what was I saying?

The relays are under the dash not least because I hate putting that cover back on.

Still thinking about that single transistor AND gate. I can't imagine the coil draws enough current with near 12 Volts across it to need bigger than a TO-92/TO-18 case transistor - BC108 or 109 - and no heatsink. The worry I have is that with the ignition off and the lights switched on, the load from the unpowered radio means the collector-base junction is indeed over-saturated and goes into thermal runaway. But a diode above the collector that's reverse biased in that situation ought to fix that. So the comp count's up to 2 transistors, two resistors, and two diodes (and a PCB). Can I get 40 Amp PCB mounted (socketed) relays to replace the ones that are being controlled by these transistors?

Graham

[MIG Wielder]

I've always remembered a quote on here from years ago.
" You don't need to worry about leaving the lights on on your Dolomite.
As you walk away you always throw an admiring glance back to where you have parked it."

Tony.

[Richard the old one]

In the next edition of Dolly Mixture you will be able to read how I fitted relays in the headlight circuits without cutting or damaging any of the cars original wires. My cars are 1977 or later 1500HL's so I am not certain my approach will work on earlier cars.