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Headlight relays the easy way

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4tecdog

4tecdog

Jedi Hopeful
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Hi Folks
Mentioned in my last post my next job was to improve the lighting on my bj8 and I was recommended to fit relays to protect the switchgear, I don't intend to fit super powerful beamers just h4 55/60 watt and on looking at the wiring it appears the wires to the headlights are in reasonable condition could have been replaced by a po as the cable is pvc not cotton covered like the majority of the wiring, My question is it feasible and easy to fit the relays on the firewall with a fused feed from the starter (starter has an integral solenoid). And are there any posts that have wiring recommendations for this job. I would prefer not to disturb the existing wiring to the headlights. Also any recommendations for added protection ie fusable link or circuit breaker on the battery. I do intend to install more protective fuses for rad fan, fuel pump etc. Keep it simple guys I'm still a learner at this classic hobby and I've just brought another so I need to learn fast!
 
I want to qualify my following remarks in that I just don't get it. Unless there are devices and experiences that I have not run into, I have rarely found the need for a relay in my automotive restoration pursuits. I have worked in the electrical field all my life and I have used relays extensively but not in my automotive pursuits.

The first thing I would like to say is that just because someone dreamed it up or the aftermarket decided to produce it and sell it doesn't mean it is a good idea or even necessary. Yes I am referring to relays. I have nothing against relays, it is just that I believe in the KISS principle. (keep it simple stup..). Second point, I can't find at the moment what the original Healey headlight wattage was, but 60 watt lights on 12 volts would draw 10 amps (5 amps ea.) thru the wiring harness and the head light dimmer switch and the headlight main switch. The wires in the headlight circuit are the heaviest wires in the whole car. I believe they are #12 AWG. #12 will handle 20 amps. So the weakest link would be the contacts in the dimmer switch and the contacts in the headlight on/off switch. By installing a relay you will not be eliminating the current thru the dimmer switch unless you are building a pretty sophisticated circuit. You will only be rerouting the heavier current from the headlight on/off switch which I believe can handle the 10 amps. And if it eventually doesn't handle the extra current just put in a new switch.
So where can you put the relay if you are determined to do it? Look at the schematic, I have posted one in a previous thread, you will see on the BJ8 that there is a blue wire coming off of the headlight switch and going to the dimmer switch. You would take this wire off the dimmer switch and make it turn the relay on and off. Then you would take a new #12 wire starting either at the voltage regulator "B" terminal or starting at the starter solenoid which is just about electrically the same point, and attach it to the input terminal on the relay switched contacts. You would then run a #12 wire from the output terminal of the relay contacts to the center point of the dimmer switch where you removed the blue wire. This would put your headlights on the relay which would be fed from the voltage regulator "B" terminal or the solenoid to thru relay, thru the dimmer switch (which you need) and then to the headlights. Your headlight switch via the blue wire would be turning the relay on and off.
 
Just doing a wiring panel for mine to achieve relay switching for the dip and main, horns, and electric fan. First off I replaced the standard bulkhead mounted fuse block with one from CBS using blade fuses. Then I have 4 relays one for each service. The power is taken as you say from the solenoid and fused at 30 Amp. This connects to a busbar with 4 fused outlets to the power side of the relay. The switch side is from the original loom and service switch . Each relay is locally earthed. I then rewired power to each service. With heavier cable and used a cotton loom tape from vehicle wiring products to make it all nice. My wiring panel will mount on the inner wing next to the splash guard. The route of the original loom makes this an ideal position.
In doing this as you realise significant load is taken off the switching circuits and the risk of burning out switches and fires is very much reduced. You'll also get better lighting as a bonus due to lower resistance.
 
Now that's what I would call the easy option, would you not fuse it at some position? I would not like a lights out situation but there again a fire would be worse.
 
do you have a pic or diagram haasad? Interested in the bulkhead mounted fuse block don't know who might supply one in UK similar to the one you describe.
 
As stated in previous post it was very rare that you would find headlights fused in early cars. I don't know what is done in modern tec cars. probably circuit breakers. Since the headlights were unfused in many vintage cars I decided it was unnecessary to fuse them. Again here is an example, Chevrolets in the 50s and 60s did not fuse their headlights, but there was a circuit breaker or you could call it an overload bimetal strip built into their head light switch. If the headlights or the circuit shorted and caused overload current, the bimetal strip would heat up and open the circuit thereby shutting off the lights. With the lights off the bimetal strip would close and restore power to the headlights. If the overcurrent still existed the bimetal strip would heat up again and shut off the lights, the cycle would continue until the fault was repaired. But the theory was that you could drive home with blinking lights. I do believe in fuses in every respect but when things have worked for 50 or 60 years or more I don't necessarily believe they need changed.
 
I can tell you that the unfused circuits on the early British cars are a fire ready to happen. Why the Brits, and maybe others, decided it was better to have a lighting circuit short out and most likely start the car on fire, rather than risk blowing a fuse and not having lights is beyond me. Yes, adding fuses as well as relays adds additional protection that could have helped avoiding burning a AH 3000 to beyond help in my garage.
Scott in CA
 
Yes, adding fuses as well as relays adds additional protection that could have helped avoiding burning a AH 3000 to beyond help in my garage.
Scott in CA

U are absolutely right-It would have prevented it-----:applause:--------:encouragement:

"N" Back in them old days them fellas were just not lectric literate N Let Lucas lead them.----:highly_amused:
 
Hi, a huge variety of fuse holders and relays etc are available. I always use Car Builder Solutions or Vehicle Woring Products.....Google is your friend đź‘Ť
 
Hi All,

Well, when I first brought my new BJ8P1 home in April of 1964, I would probably have agreed with Vette's feeling that relays and additional fuses were unnecessary. However, that was over 50 years ago and my choice of electrical options was limited to Lucas driving lights and an AM transistor radio. Over the years, components deteriorate and common connector corrosion increases resistance and heat within the harnesses to raise the needed baseline current.

Keep in mind that unless you are keeping your car fully Concourse spec, I see adding additional fusing and off-loading head/driving light power draw from passing through multiple components of the old electrical system as a positive and a major risk reducer and a good thing to do.

Here is an article that may give you some ideas “Let there be RealLight” on how relays and fuses can be added to offload the original power path and relegate the function of the original components and harness from one of control and supply to one of controlling only. https://drive.google.com/file/d/0Bx...NWRiLWFkMTYtOGMyYTgwYTQ5Y2E5/view?usp=sharing

Ray(64BJ8P1)
 
Last edited:
Keoke said:
Well OK Andrea

But why is a Green and yellow wire shown going to ground i thought all ground wire should be Black:devilgrin:
Click to expand...
Find on the bottom drawer :wink-new:(green and yellow wire is used in UE homes for TERRA connections)
 
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