headlight switch

road2speed · 03-08-2012, 07:28 AM

Hi everyone i was working on my 4000s quatro and found that the headlight switch was disconnected so i reconnected it and it works!!
My question is how can i prolong the headlight circuits life because i have herd about the wire harness frying and or the switch contacts burning ?

Rogviler · 03-08-2012, 08:15 AM

Yeah, it's always a good idea to relay them:

http://www.humanspeakers.com/audi/headlight-simple.htm

While you're at it you can relay the parking lights too, as they're about as likely to burn the switch out. Same procedure for both. If it's easier to find 5-wire relays (usually is), that's fine, just pull the wire out of the socket for the normally closed pin so it doesn't have the potential to short.

-Rog

road2speed · 03-12-2012, 09:26 AM

before i do anything to the headlights i have a few questions about re wiring them
1.the object is to create a new circuit while only using the trigger signal (white, yellow ) wires from the switch to power the realys?

2.I only need to use two relays to power the high and low beam ? why does it say no spst relay?

3.can you use different wire guages together like 12-16 or 12-18

Rogviler · 03-12-2012, 09:50 AM

Sure thing...

1. Yes. The stock wire will tell the relay to turn on, while the relay supplies its own direct power to the lights.

2a. You can either do one for the highs and one for the lows or you can split the lows for some redundancy, so in case one of them fails you'll still have at least one low beam. So three relays total if you do that. That's up to you.

2b. The "NO" refers to a "normally open" relay as opposed to a "normally closed." An NO would be "off" until it's triggered, which is what you want. The SPST is a 4-pin relay, while the SPDT is 5-pin. SPDT relays are easier to find (in my experience), and they'll work fine for this application. You just need to remove the 87a pin because it's hot until the relay is triggered, which could cause a short if left dangling. Just pull it completely out of the socket so there's nothing there for the relay pin to contact. Make sure you do get ones with sockets.

3. As long as the wire you're using is at least as big as the wiring to the headlights, it doesn't matter much. The only issue you'll run into with sizes that differ too much is if you're using crimp connectors. If you're soldering then it doesn't matter. Try to get the sizes as consistent as you can though, just for neatness. Either way, shrink tubing is a good idea.

-Rog

road2speed · 03-30-2012, 08:39 PM

gracious

03-12-2012, 09:26 AM	#3
road2speed Audiworld Junior Member Garage is empty, add now Join Date: Jan 2012 Posts: 30	noob wiring questions before i do anything to the headlights i have a few questions about re wiring them 1.the object is to create a new circuit while only using the trigger signal (white, yellow ) wires from the switch to power the realys? 2.I only need to use two relays to power the high and low beam ? why does it say no spst relay? 3.can you use different wire guages together like 12-16 or 12-18

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03-08-2012, 08:15 AM	#2
Rogviler AudiWorld Senior Member Garage is empty, add now Join Date: May 2010 Location: Colorado Posts: 748	Yeah, it's always a good idea to relay them: http://www.humanspeakers.com/audi/headlight-simple.htm While you're at it you can relay the parking lights too, as they're about as likely to burn the switch out. Same procedure for both. If it's easier to find 5-wire relays (usually is), that's fine, just pull the wire out of the socket for the normally closed pin so it doesn't have the potential to short. -Rog

03-12-2012, 09:50 AM	#4
Rogviler AudiWorld Senior Member Garage is empty, add now Join Date: May 2010 Location: Colorado Posts: 748	Sure thing... 1. Yes. The stock wire will tell the relay to turn on, while the relay supplies its own direct power to the lights. 2a. You can either do one for the highs and one for the lows or you can split the lows for some redundancy, so in case one of them fails you'll still have at least one low beam. So three relays total if you do that. That's up to you. 2b. The "NO" refers to a "normally open" relay as opposed to a "normally closed." An NO would be "off" until it's triggered, which is what you want. The SPST is a 4-pin relay, while the SPDT is 5-pin. SPDT relays are easier to find (in my experience), and they'll work fine for this application. You just need to remove the 87a pin because it's hot until the relay is triggered, which could cause a short if left dangling. Just pull it completely out of the socket so there's nothing there for the relay pin to contact. Make sure you do get ones with sockets. 3. As long as the wire you're using is at least as big as the wiring to the headlights, it doesn't matter much. The only issue you'll run into with sizes that differ too much is if you're using crimp connectors. If you're soldering then it doesn't matter. Try to get the sizes as consistent as you can though, just for neatness. Either way, shrink tubing is a good idea. -Rog

03-30-2012, 08:39 PM	#5
road2speed Audiworld Junior Member Garage is empty, add now Join Date: Jan 2012 Posts: 30	gracious

03-30-2012, 08:39 PM
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