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Lucas relays & headlamps

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Alan_Myers

Alan_Myers

Luke Skywalker
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Hi all,

I'm working out some details on my TR4 and would like to install some relays for headlights, driving lights, maybe a few other things.

I'd prefer to use "correct" older style Lucas relays, the ones with the metal cover, however I see Lucas made a wide variety of these and don't have much info about them.

Does anyone know of a source of info: relay load capability ratings, connection diagrams, etc. I'm sure certain relays were used in a wide variety of applications, it would be helpful to know some of those, too.

I'm also shopping for Lucas headlamps, 7" round, of course. One possiblity is Lucas LeMans, vertical dip halogens. Probably not really street-legal, but I ain't gonna let a little thing like that stop me!

I'd consider other Lucas, hopefully halogen with interchangeable bulbs, if anyone can suggest a model. Preferably *not* the "tripod" PL700s. Must be correct for LHD (i.e., right dip.... or vertical dip like the LeMans ;-).

Any and all assistance very much appreciated!

Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
 
Alan, I found the relay for the TR6 and TR4 horns can carry enough current for the lights with no problem, even used it on the driving lights, but just to be that little bet over done I put a in line fuse in the final power wire. This is the same relay that carries the load for the "A" overdrive, which draws a good bit of current. Alan, I was just in the MG Forum and they have a good thread going on 'To fuse or not to fuse', you will get some good info there. Wayne
 
Wayne what overdrive load are you refering too???---Keoke
 
Hello Alan,
one company you may like to try is Holden Vintage and Classic, www.holden.co.uk they stock a huge range of Lucas lighting and relays and should be able to answer most of your questions (plus ignition, starters, alternators, dynamos,etc). The majority of the metal cased relays were rated at 30 amps, and there is a model which incorporates a fuse also.
Keoke, I'm sure that Wayne means the electrical load of the solenoid, approx 20 amps initially but should be below 1 amp when energised.

Alec
 
Thanks Piman, that's what I was trying to say. Now if you are going to get really into the high amp (airplane) lights you might want to go with the '50's Chrysler starter relay, about 10 bucks from Autozone, that's what all the kids are using for the big radio amplifiers. Wayne
 
OK Piman, but that electrical load is only; Watt/Seconds{jules} it is the steady state current you want to deal with. Therefore, I would suggest using the overdrive relay for lighting circuits because its long term steady state operating current is less than 2A while its load carrying capability is quite adequate.---Keoke
 
Alan, sounds as though you really want to keep your 4 as close to Lucas as you can. However, consider going with Cibie. Just across the channel from England. (Although they might well be made in Japan now) I am running standard H4 halogen bulbs inside Cibie E-code soda crystal headlight lenses. They, unfortunately, are not legal for road use in the U.S. (They are fine in Louisiana where headlights are often a novelty.) Their high beam is truly brilliant. Below the bumper, I have mounted Cibie Airport fogs and find them just as bright. So much so that I have to aim them down somewhat to avoid blinding oncoming traffic. The fogs are wired through a Hella relay and fused totally independant of the rest of the harness. Just a thought.

Bill
 
Since the relays aren't original to the car, consider mounting them on a panel that can be tucked away in a hidden corner of the engine compartment. Lucas relays may be fine, but using Lucas means you won't be able to source replacements any easier than the rest of your car parts. If the relays are tucked out of sight, consider using the Bosch ISO style 30 Amp relays. This is probably the type TR6Bill is mentioning above. You can source these from most auto parts stores as Bosch, Hella, or generic parts.
 
Re: Lucas relays & headlamps

Hello Keoke,
I'm sorry but I don't understand your point. Certainly an overdrive relay would also be suitable for headlights. Overdrive relays are 30 amp rated and there is a significant initial current when the solenoid is energised so a lower rated relay, closer to the running curent would not last long.

Alec
 
Re: Lucas relays & headlamps

Hi Piman,I will try to clarify my comment. There are several specifications on this type relay to be considered: 1} Pullin current=19A For Milliseconds, very little power consumed. 2}Steady State Holding current=Less than 2A. 3} Contact rating = 30A. During the time after the "relay" is energized it consumes less than 2a of steady state holding current to remain on. The contacts are,Rated, capable of handling loads up to 30A.---Keoke /ubbthreads/images/graemlins/yesnod.gif
 
Re: Lucas relays & headlamps

Virtually any standard automotive 30A relay should be fine for the headlights.

To elaborate on Keoke's statements, what he's calling the "pullin current" is the necessary current to switch the device. The inrush current for a relay coil is generally insignificant to the overall picture because it's of such short duration and the size of the wiring supporting it. Of more importance is the ability of the relay contacts to handle the inrush current to the headlamps themselves. However, keep this in perspective and remember that the little Lucas switch and it's simple (generally unplated) contacts can generally handle the load. The relay holding current is indeed less than 2 amps, usually considerably less. A flow of 2 amps would indicate the relay coil had a resistance of about 7 ohms. Most relays (modern automotive ones at least) have a resistance closer to 100 ohms so the holding current is generally less than 0.2A (200 mA).

In summary, use decent sized wire and any automotive relay you want rated for 30A (or more) across it's contacts. As I mentioned in my earlier post, my preference is for the common Bosch style ISO relays available at most parts stores. They are readily availble, cheap, and generally reliable. You can also buy these (and mating sockets) from surplus sources like BG Micro.
https://www.bgmicro.com/prodinfo.asp?sid=...;time_out=44:56
and socket
https://www.bgmicro.com/prodinfo.asp?sid=...;time_out=44:57
 
Re: Lucas relays & headlamps

/ubbthreads/images/graemlins/nonono.gif DK, I know the difference between Inrush current in a reactive circuit and what these relays use.They contain two coils 1} Pullin and 2}Holding coil.I meant just what I said--Keoke /ubbthreads/images/graemlins/yesnod.gif
 
Re: Lucas relays & headlamps

I've cut open many relays Keoke, automotive and industrial control type. I've never seen "two coils". What relays have you seen with two coils and how are they wired? Do they have extra terminals? The term "pullin" as I've seen it used with relays typically is applied to the "must have" current or voltage to make it switch.
 
Re: Lucas relays & headlamps

Well DK, you better cut up a few more cuz you missed the gooduns.---Keoke /ubbthreads/images/graemlins/wink.gif
 
Re: Lucas relays & headlamps

Well, the problem here is Keoke is talking about the OD solenoid, and DK is talking about the control relay.

Relays don't have dual coils (with possible rare exceptions); the OD solenoids do.
 
Re: Lucas relays & headlamps

Thanks for the clarification Danmas.
 
Re: Lucas relays & headlamps

HI Danmass, The type relay I am refering to is more commonly called a Latching relay.They do contain one coil or two if you use the most energy efficient one.---Keoke
 
Re: Lucas relays & headlamps

Hi, Keoke,

The only two-coil latching relays I'm familiar with use one coil to SET and the other to RESET. I can't imagine a relay coil drawing enough current to require both a pull-in and a holding coil. Before a relay that large would be used, I would imagine a magnetic starter would be used instead.

I could be wrong. Do you have any model numbers for a dual-coil relay with pull-in and holding coils? I'd be curious as to the application for such a relay.
 
Re: Lucas relays & headlamps

Yeah I have a special "AC" project non automotive Which uses a relay from Digi_Key with initial part number 255-1443-ND that I am looking at---Keoke
 
Re: Lucas relays & headlamps

Hi, Keoke,

The relay that you referenced - 255-1443-ND - is a latching relay with set and reset coils, not pull-in and holding. I couldn't find one in that list with those type coils.
 
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