MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

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turn signal switch wiring
Posted by: rficalora
Date: June 27, 2010 06:16PM

Finishing up the wiring... ''76 turn signal/dimmer/flash-to-pass switch. Wiring digram shows what looks like two power leads -- purple from the fuse box & solid blue from the headlight switch. Info I got from MG Experience board was blue is power feed to dimmer & purple is power feed for high-beam "flash" function. My wiring harness doesn't have a 'flash to pass' wire, just dimmer power. So, I'm thinking the dimmer power goes to the blue wire on the swtich. And, I can either not use the flash to pass function or run another (suitable gauge) hot wire to the purple wire to enable the flash to pass. Sound right?


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

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Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 02, 2010 02:16AM

Hey Rob,
You are absolutely correct on the wiring. The blue wire is hot with the head lamp switch on and the purple wire supplies the flash to pass feature. The only caveat is do not feed the flash to pass from an ign source. This will cause the ign to be powered when the high beams are on. Use a constant power source and fuse it at 15 amps.
Cheers
Fred


rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: turn signal switch wiring
Posted by: rficalora
Date: July 02, 2010 09:22AM

Thanks Fred. I talked with the wiring harness support guy & he recommended picking up power for the flash to pass from the "accessory 2" circuit. That way it's constant power whenever the ignition is on but shuts off when starting.


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

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Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 02, 2010 08:12PM

Hi Rob, while it is a small problem it can have serious repercussions. Powering the flash to pass through the accy power will leave you with an unexpected backfeed problem. With the key off and the headlights on, if you flash to pass, the accys will get power through the headlight dimmer switch. This is a minor annoyance except that the dimmer switch won't carry that load for long and will melt. You would be better off to give it constant power. I would use the power feed to the headlight switch as it's nearby and correctly fused.
Cheers
Fred


rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: turn signal switch wiring
Posted by: rficalora
Date: July 03, 2010 01:05PM

Interesting. Thanks for that info Fred -- and it does make sense. If I use the headlight power lead & flash to pass when headlights are on, both low & high beams would be simultaneously running off that same power lead. Do you know how many amps the total would be? I'm using an after market universal hot rod type harness & want to make sure the wire is gauged/fused appropriately.

Rob


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: turn signal switch wiring
Posted by: BlownMGB-V8
Date: July 04, 2010 09:37AM

Divide wattage by system voltage to get amps. So a 100 watt (may or may not be legal) bulb is going to draw something less than 10 amps.

JB


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 05, 2010 02:07AM

Rob, lets say you maxed out your headlights. The baddest ones you can get are 100w high and 65w low so thats 330 watts total. Then add in your park lights, assume 5 to 10 watts per corner for another 40 watts. Thats 370 watts combined divide by 12 volts and you get roughly 31amps. I wouldn't feed that load with less than a 14 guage wire and would feel better with a 12 guage.
Fuses would be 35amp with 14 guage wire and 40 amp with 12 guage. At this level of draw you should be using relays to reduce the load on the switches.
However in the real world, high beam would be 65w x 2 and running lights at 5w x 4 for a draw of 12.5 amps. With the intermittant nature of the flash to pass feature 14 guage wire and a 20 amp fuse should work just fine.
Cheers
Fred



rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

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Re: turn signal switch wiring
Posted by: rficalora
Date: July 05, 2010 01:28PM

Great. Did some research & verified my headlights are standard H-4 50/65 watt. I currently have my headlights wired through a relay & using a toggle switch to turn them on & off. They are wired as below. Sounds like all I need to do is tap into the headlight power wire (in burgandy below). Make sense?
Headlight wiring.jpg


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 05, 2010 03:04PM

Yep thats perfect.

Remember if you can't resistor may capacitor.

Cheers
Fred


rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: turn signal switch wiring
Posted by: rficalora
Date: July 05, 2010 04:15PM

Thanks Frank. Big help.

If you're up for it, let's go one step further... as wired, the dimmer/flash to pass will be getting the full headlight current. Is the diagram below what I'd need to do to avoid that? And, is there a standard for how much current a relay draws on the switch line? If it's low enough, I can probably eliminate the relay I'm currently using to protect the toggle switch. It's a 20A switch so if I can, that would eliminate an unnecessary failure point.
Headlight wiring with relays for high & low beams.jpg



Edited 1 time(s). Last edit at 07/05/2010 04:20PM by rficalora.


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 06, 2010 04:08AM

Ok Rob, in this diagram your original relay becomes redundant. The only load that it has to carry is the dash and park lights.The headlight switch can handle that easily. You can eliminate the first relay and live happily ever after.

But if you really want to do it right, lets mount both relays as close to the headlights as possible. The radiator support bulkhead is a good choice. Ground both 30s, 86s and 87s are wired as per your diagram. Run fused battery power to the headlights black wire (previously ground) Use separate fuses for left and right headlights. Mount your third relay with the first two. Supply it's 30 and all three 85s with fused battery power (or accy power if you want the lights to turn off with the key). This third relays 87 will be power to the park and dash lights. 86 goes to your headlight switch along with the flash to pass and the dimmer power wires. The other side of the headlight switch gets grounded.
What all of this does is remove all the load carrying and hot wires from the passenger compartment as your switches now only control grounds. It also leaves you with some form of lighting if a fuse blows.

Isn't this fun?

Cheers
Fred


rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: turn signal switch wiring
Posted by: rficalora
Date: July 07, 2010 08:53PM

Ok Fred, I think I get the concept - and I like the idea of getting the high current leads closer to the lights/out of the cockpit. I have a couple of questions that will help ensure I'm following you (I've traced wiring digrams to find/fix problems, but have never messed with relays till now).

Question 1:
I've diagramed what I think you said, so 1st, did I get it right?
Headlight wiring with switch controlling ground.jpg

Making sure I understand the operation:
---------------------------------------------------------
Flipping the toggle switch completes the 85/86 circuit in relay #1. In this position, the relay is "energized" so 30/87 are connected providing power to tail lights, park lights, & instrument panel lights.

Dimmer Power on the dimmer/flash-to-pass switch is now also grounded which completes the 85/86 circuit in either relay #1 or relay #2 -- depending on the dimmer switch position. The correspoinding relay's 30/87 are thus connected so either low or high beams are on -- and switch between them based on the position of the dimmer switch.

The flash-to-pass lead on the dimmer/flash-to-pass switch is also now grounded so when the flash-to-pass switch is pulled (connection made), relay #1's terminal 86 is grounded so the high-beams come on.

Question 2:
If the toggle switch is open, the flash-to-pass is not grounded so relay #1 would not energize. Should the flash-to-pass lead on the switch go straight to ground so that function works even when headllght switch is off?

Question 3:
If I have all this right, the hot leads in my wiring harness for headlight power and dimmer power are no longer needed & should be removed/appropirately capped off. Right?

Rob



Edited 1 time(s). Last edit at 07/07/2010 08:55PM by rficalora.


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 08, 2010 03:10PM

Excellent Rob. You have grasped the concept relay relay well.
You are right the flash to pass should go to a permanent ground.
Sorry for the error, must be the Coors kicking in. I'll get the lovely Lynne to punish me apropriately.
The fuse for the park lights can be much smaller. total draw on the system will be around 3-4 amps so a 10 amp fuse would be more than enough.( the relays draw 0.2amps each, dash lights are 0.25 amps each and park bulbs are 0.5 amps each ) Max draw for the headlights is 10 amps so a 15 amp fuse for each light would work well. You could power the high / low relays from the headlamp fuses so that a blown park fuse won't leave you completely in the dark.
Yes your current power leads are unused, cap them or use them for something else. Sound system comes to mind.
See what I mean about not having any high draw hot leads inside the passenger compartment and brighter lights to boot? You also would have to blow all three fuses to lose all of your lighting.
Did you think about powering the relays through the accy or ign? That way you can't leave your lights on. You could even split it up and have full time park and keyed headlights, or full time low and keyed high and park or...... wait a minute....Coors kicking in again.
Cheers
Fred


rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: turn signal switch wiring
Posted by: rficalora
Date: July 08, 2010 03:25PM

Cool. Thanks again. Now if I can get through surgery tomorrow (2nd one in 1 week -- $#@&!) & feel better by the weekend I can finish the last of the wiring.

By the way, what's "two strokes" refer to?


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: turn signal switch wiring
Posted by: DiDueColpi
Date: July 08, 2010 04:45PM

Nicely done Rob
Few people have figured that one out before.
I used to build and race go karts and got the nickname "twostroke" for taking the rules to a new level when I built engines.
Nowadays I collect old Italian scooters so DiDueColpi fit and it's cheeky enough to be fun.
Cheers
Hope the surgery goes well
Fred



rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: turn signal switch wiring
Posted by: rficalora
Date: December 11, 2010 11:44PM

Hi Fred, I hope you don't mind me re-surfacing this thread seeking some more info... I still have the single relay inside the cabin but am getting ready to make this change. I added the hazzard switch to the diagram -- it's constant power to the hazzard flasher; other side of the flasher goes to a toggle switch; other side of the toggle ties into the 87 on the 3rd relay (provides power to park & dash lights when headlights are on). But, looks like by doing that, the dash lights will blink with the hazzards.

To correct that, I changed the dash lights --- +12v for the dash lights comes from Accessory power (same as feeds to the 85's on all three relays); ground side of dash lights ties into the wire that runs from the headlight toggle to the dimmer [labeled "Dimmer Power" in the diagram above. That way the circuit is completed when the headlights are on, but the dash lights aren't in the path of the hazzard flasher. Make sense?

Last, a question about the accessory power feeding the three relay 85's... That wire will run from the fuse box up to the front of the car. Should I run a seperate wire for each relay or run one wire to the front & split it to feed all three relays up where they are? Seems like it'd be better to have three seperate leads because if that wire were to short, I'd lose all lighting. If I run seperate wires (even though that'll be a pain), I'll still have some lighting even if one were to short.


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: turn signal switch wiring
Posted by: DiDueColpi
Date: December 13, 2010 03:10AM

No problem Rob. Good to see you working on the car.
You should really have the hazzard on the signals not the park lights. It's very easy to hook up. Just use your powered hazzard flasher and a dual pole toggle switch. Bridge the top two poles of the switch together and connect them to the output of the hazzard flasher. The bottom poles go to the left and right outputs at the signal switch. ( I don't have the wire colours handy at the moment) With the toggle off the signals work normally, with it on, everything is tied together and all the signal lights flash.
With the lighting relays it depends on how you want to fuse them. Running three wires won't buy you anything if they are all on the same fuse. Fuse them all separately and your in business.
Cheers
Fred


smelfi
Steve Melfi
Alexandria Ohio
(90 posts)

Registered:
04/26/2008 07:35AM

Main British Car:
1977 MGB 302

authors avatar
Re: turn signal switch wiring
Posted by: smelfi
Date: December 13, 2010 10:18AM

Rob,
Here's a site with quite a few Automotive circuit how to's.

[www.the12volt.com]

Steve


mgbazza
Barrie Egerton
Sydney Australia
(24 posts)

Registered:
01/20/2009 07:40AM

Main British Car:
1978 MGB GT Rover 3.5

Re: turn signal switch wiring
Posted by: mgbazza
Date: December 14, 2010 08:04PM

Rob, the " flash to pass" has to work independently of the lighting system. It's used as an alternative to the horn & should be wired from a permanently hot source , ie. the purple cct. so it can be used in daylight as well. Your first post said it all. The switch will direct the current directly to the high beam cct. blue/white. Barrie E


mgbazza
Barrie Egerton
Sydney Australia
(24 posts)

Registered:
01/20/2009 07:40AM

Main British Car:
1978 MGB GT Rover 3.5

Re: turn signal switch wiring
Posted by: mgbazza
Date: December 15, 2010 01:29AM

Rob how do you manage such neat diagrams ? Barrie E
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