Modern cars...Headlamp relays??

[cardiffrob]

Does anyone with knowledge of modern cars have a list in their head of some cars that use relays to feed the headlamps? I was wondering how many of them these days feed power through the switch and how many have to 'relay' the amps.
I have just fitted an old floor-mounted dipswitch to the Morris after the repro one died from burnt contacts.
Thanks.
Rob.

PS Does anyone have a source of genuine Lucas Wiring Loom Smoke? Mine has all leaked out.

 

[rtbcomp]

Most of them will. Metros spring to mind, but you did specify modern, and cars.

If you want to fit new ones have a look here, https://www.beal.org.uk/automotive/automotive-relays.html

 

[Lufbramatt]

I know 80's/90's era Volkswagens feed all the power through the switch, leading to dull headlights and very hot switches as the cars get older.

I made a relay loom, triggered by the original headlight wiring, so the lamps get full voltage rather than the 10 and a bit volts they were getting before. Used a standard 30 amp automotive relay and an inline fuse for each bulb.

 

[Robotstar5]

PS Does anyone have a source of genuine Lucas Wiring Loom Smoke? Mine has all leaked out.

Replacement Lucas smoke available here

 

[cardiffrob]

I wondered how long it would take!!

Anyways, I was curious as to whether new cars were going for thinner wiring and relays or thicker wiring and better switch-gear so I could see if there was anything worth pinching off of a modern car to sort out the Morris. I've already gone for LED rear lights to stop the cheapo knock-off chinese brake light switches from burning out, a common Morris fault these days.

 

[johnik]

prob easiest to us 2X 4 pin relays, that way the switches only switch the relay and dont carry the full current,most modern stuff will have a special relay for that kind of stuff with 1000 terminals and a price tag to match.

 

[steveo3002]

easy enough to make something up

or our chinese freinds have some affordable ones on ebay if you search headlamp relay harness and suchlike

http://www.ebay.co.uk/itm/H4-Headli...042537?hash=item3d0c75a8a9:g:kbkAAOxy0bRTFaJF

 

[rtbcomp]

Is your Moggy +ve earth? If so be careful, some relays have a diode across the coil and they are designed for modern -ve earth systems.

 

[cardiffrob]

I'm on negative earth and have bags of relays here. On the Healey Coupe I used a hefty switch with a 4 pin for the headlamp feed then a 5 pin switchover to the bulbs so that if the dip switch died again it would default to dipped beam rather than going dark. I learned that lesson on a dark B-road about 15 years ago!

I'm not necessarily going to change much but wondered what the modern thinking was for solving the problem of dodgy lights. Thicker terminals or relays? I see the Mondeo has a headlamp relay in it. The Merc here with those HID lamps probably is relayed due to the huge output of those lights. Is that the most common way to do it these days?

Tehe MGC had some big Maxi fuses and a row of relays with thick wiring to cope with the extra wattage of the lights. The original loom went 'phut' when I tried to improve the dim glow from the H4s. You can see the heavier gauge wiring to reduce the voltage drop. every little bit helps!

 

[rtbcomp]

On my Landrover I mounted headlamp relays near the battery (at the front of the vehicle) and used thick wire to feed the lamps and thin wire back to the switches. The relays had built-in fuse holders.

Another advantage of using relays is that you can feed the headlamp circuit through the ignition switch.

 

[optima21]

relayed headlamp looms are pretty easy to make, here's one that I made a few years ago for one of my VW Polo's. this is the finished loom. just to confuse you, the red and brown leads in the middle of the picture are connected directly to the battery, but on VW's brown is a earth wire connected to the battery negative terminal (or bodywork) , but on British cars the brown is connected to the battery positive terminal.

I took the feed to power the relay from the original headlight switch, using the original connections on the fusebox (the white and yellow wires for the dipped and main beams).

then used them to switch the relays on which were located by the battery and connected directly to it. I used fused relays as it made the installation neater.

and the high current wires from relays were connected to the lights

modern wiring on cars is often "thin wall" which has a smaller diameter conductor and really thin insulator, so a wire that is 3.3mm overall diameter, may be 17.5 amp if its traditional cable, but could also 33 amp if its thin walled.

One issue that I did have was that I kept blowing the led in clocks that show when the main beam was swicthed on, so I ended up having to wire in a diode across the relay coil to stop this happening.

on my Triumph Herald, the wiring will be a bit more complicated, as I need an a third relay to turn off the dipped beam in case I need to flash someone. on the original loom, if you flash the main beam using the steering column stalk switch, it keeps the dipped beam on and works the main beam too.

also it would appear that british cars have standardised colour wiring, but not sure how true this is

http://www.autoelectricsupplies.co.uk/cms/files/colour_code_for_vehicle_wiring_-_new_order_2.pdf

 

[rtbcomp]

That colour code refers to the British Leyland type cars, British Fords (Cortinas, Anglias &c) use a different colour code. Don't know about later models or other makes.

 

[colnerov]

Hi, HID lights draw about half the power of incandescent (ordinary) lamps. However it's not advisable to replace them in old light units, the problem is the the light source is bigger than the filament it replaces so it's not in the focal point of the reflector and you end up with a lot of light scatter. HID light units are designed specifically to cater for this. This is why some headlights on cars coming the other way dazzle you because someone has fitted HIDs in ordinary lights.

Colin

 

[colnerov]

That colour code refers to the British Leyland type cars, British Fords (Cortinas, Anglias &c) use a different colour code. Don't know about later models or other makes.

Hi, Yes, British Fords went away from it in the mid 70s. I think it may be different again on the Canbus system.

Colin

 

[Justme]

Most new cars will be canbus controlled.

 

[wookie]

I have just fitted an old floor-mounted dipswitch to the Morris after the repro one died from burnt contacts.

I've found a lot of these repro switches manage to give LUCAS a good name, since they are even more unreliable than the LUCAS ones they replace. My preference is now to refurbish original LUCAS switch gear whenever possible and avoid repro like the plague

 

[500e]

Hella relays are a sound bet 5pin spdt