Please check lighting relay plan

[tomfreo]

I noticed the other night with the headlights on, that the contacts on the back of original light switch (1961 6V beetle) were very hot, enough to burn.

I've taken the switch apart a number of times to clean it up and don't think I'm going to get it working any better than it is now.

I installed 55/60W halogens a while ago which may account for the heat generated at the switch.

I happen to have a couple of unused 40A 6V relays and thought maybe I should save the original headlight switch and install the relays.

I've done a little research and drawn a provisional wiring diagram (of sorts!). I was hoping someone with a little more know-how than me re. wiring might have a look and tell me how it might be improved.

Some things I'm unsure of:
1) Are the relays in the right place? Some people I see use just one relay before the dimmer and bypass *just* the headlight switch.
2) Is the wire gauge right? (I haven't checked to see if there'll be a problem getting the wire through to the headlights; I'm hoping I won't have to remove the original wiring).
3) Is a ground returned to the neg terminal of the battery overkill?
3) Is it fused properly?
4) Is there something I'm missing re. a fuse blowing or other mishap that could leave me flying blind at night?

BTW, you might notice "direct line from battery" going to #8 fuse. This was installed by the previous owner. It's a pretty big wire and I did consider repurposing it for the lighting relay but am a bit loath to do that.

Thanks!

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'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[herbie1200]

Dear tomfreo, my comments:

1) you should change the 25A fuse with a 70-80A fuse directly from the battery; this fuse is only in case of short circuit to avoid fire. But you don't want to be without lights for a single fuse failure.

2) OK for the relais rearrangement but you should give command to the relais BEFORE the original fuses; in other terms you should connect the terms out from the original dimmer DIRECTLY to the two relais' coils.

3) THEN, I suggest you to connect relais outputs to the fuse 2-3 and 4-5 inlets (the upper side), so you reuse original fuses array.

Obviously you have to reconnect the lamp wires on their original position on the fusebox.

Also change the 4 fuses from 8 to 16A, to accomplish new 55/60W lamps.

You need all 4 fuses for a safety issue; if a fuse blows, you still have some light, during night driving it's a life-related issue.

Tell me if something is not clear or seems wrong to you.

[tomfreo]

Thanks for your suggestions. I understand the suggested changes. I've updated the wiring plan accordingly.

Do you think the wire size is sufficient? I stopped to look at wire available at a local shop and am wondering if I shouldn't go larger: maybe 12G from battery to relay and from relay to lights ...?

_________________
_________________
'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[VOLKSWAGNUT]

The amended schematic is better. . ...but the relay LARGE ground gauge and ground path back to the battery is WAY overkill just to control the relay coil..

The dimmer now functions as low current relay control voltage supply.. and the relay ground is low current relay control ground..
The control side of a relay requires very little amperage..

The only serious load and current is for the actual lamps.. that is really the only circuit that needs be supplied by a direct battery connection.

I personally think the main 75A supply fuse it too large.. in addition the main fuse should be placed as close to the battery as possible.
Each lamp will use about 12 amps max surge .. so thats 24 amps for both high beams. .. .. a 50 amp main lamp supply fuse will offer plenty of protection. .

As for wire size..
12 gauge for the main from the battery
14 gauge for each lamp circuit.
18-22 gauge for the control circuit.. (or the original wiring is more than adequate).

Other than that.. (and slight schematic mistakes ) ..
Looks like you are on the right track.


.
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aka Ken {o\!/o}
Its your vehicle- stop askin' for approval-do what YOU like for cryin' out loud
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Its about the going not the showing
Rebuilt to drive not decorate
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[Zwitterkafer]

I'm not keen on the single 75A fuse. There should be two somewhat smaller fuses instead, close to the battery, on separate feed lines to each relay. That way, if a fuse blows, you'll lose only high or low beam but not both. Don't fuse ahead of the light switch, for basically the same safety reason. And yes, the relay grounds do not need to go back to the battery, just good clean connection to body ground.
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[tomfreo]

Thanks for all your suggestions. Of course I see the relays don't need a large return ground to the battery, but I'm thinking the lights do.

I'm not sure having separate feeds from the battery for each relay is really necessary. A greater source of worry, I think, is probably the unfused feed to the light switch. If there's a break in the circuit before the switch I lose everything (tho maybe ensuing fire will provide illumination!).

Having said that, I'd be interested in hearing the arguments for and against a separate feed to each relay; and what you think about fusing the circuit from the battery before it reaches the light switch (via starter motor, voltage regulator, ignition switch - note, I moved the circuit from light switch to ignition switch --> ignition switch to light switch.)

Amended plan:

_________________
_________________
'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[tasb]

Coincidently this was just posted in the oval forum:

http://www.thesamba.com/vw/forum/viewtopic.php?t=655454
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Roads Scholar &
1957 Kombi low mileage 36 hp governor equipped M 178 Slow Drag Winner 2014, 2015, 2018

1965 hardtop Deluxe Microbus owned since 1990 M 620 factory 12 v 1500cc

1961 (October)Single Cab- Road Trip Workhorse

[herbie1200]

Ok for the new ground wire arrangement.

About the fuse: this is a fuse that NEVER has to blow, because lights are already protected by the original fuses.

I have chosen a 70A because if you have the 'lamp' switch working (or, with such a relais configuration, very simple to add) you have both high + low beam lighting together, so 24+24=48A.

AND I used the 70A line also for an additional horn.

Dual line from battery makes sense if you suspect that 70A fuse could blow, to avoid no lights, but this is there only against extreme condition.

I put my big fuse only to avoid fire in case of hard collision when the wire gets exposed and touch the chassis.

[VOLKSWAGNUT]

Wiring and opinions... one thing is certain.. you will read various opinions and various suggestions. Most of which can be considered valid.
More that one way to string a bug..

Note...

18 gauge from the relays to the lamps fuses is too small as well as the T splice at the Low and High relays.

Note, keep in mind that EACH relay to fuse load circuit will be powering two bulb elements.
Low beams at 55w will consume approx 9 amps each 9x2= 18 amps. .
High Beams at 60W will consume approx 10 amps each 10x2= 20 amps.

Too many sustained on amps for 18 gauge, as the wire will now be a choke, cause heat and resistance.. something I think you are trying to over come to begin with.

Safe is 12 gauge for the main from the battery to the relays
and
14 gauge from each relays to their respective two fuses.
That above is IMO but it really depends on the wire material and circuit length.
I recommend use 12 gauge for the main, as I can right now, only assume it will be the longest wire, copper, and routed from the battery to some sort of relay junction under the hood.
12 gauge will have will have less voltage drop over the length.


No real need to fuse main battery feed high and low beam relays separately..
but.. two main fuses would be fine as well albeit more parts and time..
The chances a main fuse will blow during regular use is rare.
I can understand the high/low safety factor..

As herbie1200 noted, the new added main battery feed fuse is primarily in the event of a major failure in an accident or IF the new main battery feed would rarely and oddly short to ground.
I can understand now why herbie1200 suggested a 70 amp fuse.. in the event you want to have the option of using both high and low beams ON together or adding other accessories to that supply circuit.
Here in the USA that is an "illegal" option. High and lows can not be on at the same time and neither should high beams and fog lamps..
Now that being mentioned.. rarely is that ever policed..
and
Each lamp and each beam circuit are protected by their independent fuse at the fuse block.. (4 fuses) on down the line.

Still. IMO.. 70-75 amps protection is quite a lot... and too much for 12-14 gauge wire.
Food for thought.. .. If a fuse is too large and doesn't blow.. the actual wire is now the fuse.
The fuse should be no more than the wire can sustain and/or the measured MAX current of the circuit multiplied by 1.5.


Regarding the lamp ground wire back to the battery.. eh' depends..

If the body and chassis grounds are good, grounding the lamps to the BODY near the lamps (not the fender) is the lowest resistance back to the battery. Adding a ground circuit back to the battery is actually adding resistance and wiring work not needed.
The body sheet metal is the largest ground wire on the car..
If you have rust and resistance or BODY voltage drop issues then yes use another 12 gauge circuit for the lamp grounds back to the battery.

Regarding fusing the original battery circuits.
Adding fuses always offers more protection... period..

Keep in mind VW originally routed the main unfused battery feed to the headlamp switch FIRST then had an unfused jumper from the lamp switch to the fuse block and ignition switch.

Your schematic is altered slightly from the original "VW way".. which is fine..
If you want to add a fuse to the the main battery feed to the ignition switch/fuse block.. that is surely an option.
It would need to be large enough not to blow for starter solenoid and accessory surges but small enough to offer some protection.
Its really not necessary but is an option.
Too big.. in the event of a short, the wires become the fuse, ... too small and when (not if) the fuse pops suddenly, it kills the entire cars ignition/battery supply.. Not a good thing.. if unwarranted.

Basic fuse rule of thumb to determine a fuse size. .. measure the max current load on a circuit and multiply measurement by 1.5.
If I were to add main battery.. it would have to be large only to protect in an extreme situation.

If you want to add a fuse to the light switch feed you can and it's not a bad idea at this point. It will protect the new low current dimmer relay control circuits as well as the normally unfused parking lamps and dash lamps, in addition it will double protect the normally fused tail and license circuits.

Of topic track a little.. One thing I do... I do always add an in line fuse at the front of the car to the ignition coil circuit.... just in case.....

Suggestion... On the next amendment... title the relays "H R " and "L R"

.
_________________
aka Ken {o\!/o}
Its your vehicle- stop askin' for approval-do what YOU like for cryin' out loud
Better to roll em' how you want and wear em' out-than lettin' em' rot out
Its about the going not the showing
Rebuilt to drive not decorate
WANTED: Local Eatin' Joints, Triple D for TheSamba contributions here http://www.thesamba.com/vw/forum/viewtopic.php?t=570510
Search "VOLKSWAGNUT" on YouTube since you cant watch a "certain" BELT change video round here
Usually and often edited

[tomfreo]

Thanks again everyone for helping.

A couple of things I'm still unsure about. I want to fuse the main feed wire to the relays, and believe it will protect against overload/open circuit along the wire from the battery through the relays to the fuse panel. Question is, how to calculate the required size of fuse?

I won't be using hi-beam/lo-beam together (didn't even realize it was possible!), and won't be using this circuit to power anything but the headlights. I don't see myself getting bulbs any bigger than 55/60W, so that's a max load of 20A.

But as herbie1200 noted, I only really need to protect against a 'major failure'. And as Volkswagnut said, you don't want the wire itself acting as a fuse which might happen if the fuse itself is too large.

So how to calculate/estimate the fuse size? Possible issues are the fact that the proposed wire size from the relays to the fuse box is lighter gauge than that feeding the relays.

Volkswagnut >> The fuse should be no more than the wire can sustain and/or the measured MAX current of the circuit multiplied by 1.5.

I think in this situation, because each headlights is protected by a 16A fuse (thanks herbie1200) I need to choose a fuse for the main feed based on how many amps the wire/s can sustain.

I've done a bit of extra reading but advice on how to calculate fuse size based on wire size is conflicting. Some sites recommended a max fuse size of 20A for 12G wire which seems grossly conservative. Others mention a 'fusing capacity' of 235A for 12G wire which seems more probable but I'm not sure I want to base a decision on that.

And again, should I be basing my decision on the 12G wire to the relays, or the proposed 14G to the fuse box? And does wire length matter in this regard?

I'm thinking I might want to simply put in a c.40-50A fuse thinking that amount of current is not likely to fuse even the 14G wire. But I'm just guessing. Then again, a local shop does a good deal on 70A circuit breakers which could be nicely installed near the battery.

Volkswagnut >> Regarding the lamp ground wire back to the battery..

I'd always assumed the best way (ignoring cost/fitting issues) to ground a load would be to run a fat wire back to the battery, so I was a bit sceptical when I read that "body and chassis grounds [offer] the lowest resistance back to the battery".

After a bit of reading, seems there are partisans of both methods but I can now say I believe chassis grounding's the way to go.

BTW, Volkswagnut, why do you fuse the coil in particular?

Amended plan:

_________________
_________________
'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[VOLKSWAGNUT]

[flyboy161]

Okay, I'm going to play devil's advocate here:
First of all I'm an aircraft electrician by trade and I see what you're trying to do but, and there is always a big but, I just have a couple of questions

1. Are you still using the foot switch as a dimmer switch?

2. Why not just buy a new headlight switch.

When I first bought my '64 I opened up the hood and found this mess at the fuse block.

P.O. Had run 2 wires shown as dark brown and white cloth bound house wiring. Dark brown went to terminal 50 on the ignition switch from terminal 50 on the solenoid and white from battery + to fuse 8. The red wire wire from the solenoid to the starter solenoid that was supposed to go to terminal 50 on the ignition switch was bypassed. It was a mess. This is a classic way to "fix" a hard start situation.
I say verily to thee, there is nothing wrong with the original wiring. I did two things. One, remove the prior owner added house wiring and two put it back to stock configuration. Three replace fuse block. The new fuse block fixed all my woes. No hard start, bright headlights etc.

Your problem is heat at the back of the headlight switch. Heat is caused by resistance. Light bulbs are resistance and so they get hot. Light switches are NOT resistors and so they do not get hot. If they do get hot, they are bad and must be changed...not cleaned. Cleaning the guts of a headlight switch is just a temporary fix.

So let's look at your wiring...come on, follow along with me

Normal situation: power goes from battery to solenoid to generator to terminal 58b on the headlight switch and then to the fuse block (fuse 8 ). From their it returns to ignition switch.

You pull the headlight switch on and power feeds through the headlight switch to the dimmer switch via a black and white striped wire. At the dimmer switch it goes to the yellow wire back to fuse 4. Fuse four splits the current between fuse 4 and fuse 5 and then feeds the low beams via yellow wires respectively.

If you press and release the dimmer switch it now routes to a white wire from the dimmer to fuse 2 which again splits current to fuse 2 and 3 and sends power to each high beam respectively.

Each 55W bulb draws approximately 9 amps. Downstream of the fuses. 18 amps together up stream of the fuse. So 18 amps travels from battery through headlight switch to dimmer switch to fuse. Wow!

In theory no heat is generated until the power hits the headlight bulb. What you are proposing is complicated.

So why do we install relays? To get a shorter more direct power to the headlights. To reduce the amount of current through the headlight switch. Now your relay coils are the current draw and the switch terminals are just a feed through.

My advice, fix the stock form of lighting in three steps:
1. New headlight switch
2. New fuse block
3. Redo the terminal spade connectors at the headlight switch with some GOOD quality crimp on connectors.

Your headlights will be plenty bright and you will be using stock wiring. I run 6 volts through stock wiring and this is how my headlights look.

Most people think my car is 12 volt because it is so bright.

Like I said, just my 2 cents
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http://www.thesamba.com/vw/forum/viewtopic.php?t=603879

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http://www.thesamba.com/vw/forum/viewtopic.php?t=612776

My 1958 Morocco Bug-
http://www.thesamba.com/vw/forum/viewtopic.php?t=611483

[flyboy161]

And I do agree with adding a fuse to the coil wiring as close to the fuse block as possible. Actually on the wire coming from terminal 15/54 on the ignition switch and goes to fuse 1
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My father's 1970 Beetle-
http://www.thesamba.com/vw/forum/viewtopic.php?t=603879

The 1964...Diamond in the rough
http://www.thesamba.com/vw/forum/viewtopic.php?t=612776

My 1958 Morocco Bug-
http://www.thesamba.com/vw/forum/viewtopic.php?t=611483

[VOLKSWAGNUT]

[flyboy161]

I see what you're saying, but still believe the solution is to fix the problem. The difference in amperage is about 6.5 amps passing through the headlight switch. Better to replace the switch, soldered connections than to add to a well designed circuit. In later model beetles did they change the wiring size? No. They added a relay, but the circuit still was wired the same through the headlight switch. The power for the dimmer relay came from the flasher relay through the turn signal switch.

The resistance is still at the switch in either case and only a new switch and clean connections will eliminate that problem.

And yes, I installed a fused relay for my fog lights on my Jeep, but only because I did not want that much amperage running through the firewall to the switch and back again.
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My father's 1970 Beetle-
http://www.thesamba.com/vw/forum/viewtopic.php?t=603879

The 1964...Diamond in the rough
http://www.thesamba.com/vw/forum/viewtopic.php?t=612776

My 1958 Morocco Bug-
http://www.thesamba.com/vw/forum/viewtopic.php?t=611483

[VOLKSWAGNUT]

[flyboy161]

It's all good, I was just giving my opinion.
_________________
My father's 1970 Beetle-
http://www.thesamba.com/vw/forum/viewtopic.php?t=603879

The 1964...Diamond in the rough
http://www.thesamba.com/vw/forum/viewtopic.php?t=612776

My 1958 Morocco Bug-
http://www.thesamba.com/vw/forum/viewtopic.php?t=611483

[VOLKSWAGNUT]

[herbie1200]

Perhaps I was not clear in my "high + low beam" explaination.

This condition is not stable but ONLY when a "pass" button is depressed.

All modern cars have a switch to make "pass" lamps with high beam while low beam remains on.

If I remember well also some old Bosch-VW dimmer relays are so designed: while the "S" signal is on, both high+low output are on; than when S is released remains only the high or low output. Just one second buth enough to burn a 50A fuse with 48A... use the >70A fuse.

[KTPhil]