relay experts..

[CJL 10+ year member]

I want to add fog lights to my car,I want them to be on when my parking lights are applied but to shutoff when the headlights are on..

Is there a way using relays to make this happen?

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[Slayerx 10+ year member]

just use a separate toggle switch, will save you a huge headache.

 

[fasfocus00 5,000+ posts]

IIRC this is gonna take 3 relays, one to the fog lights and one to the headlights and one that will trigger between the fog lights and headlights.

 

[mikelaubach 10+ year member]

Is this like the movie 'Hackers' where they try to one-up each other? "I can do it with two relays." LOL

Normally open relay from the turn signals to a normally closed relay to the fog lights. No lights on, then no fog lights. When you turn on the markers, the normally open relay closes and passes power through the normally closed relay to the fogs. When you turn on the headlights, the normally closed relay opens and breaks power to the fogs.

Slayerx is right however, a switch really is easier. FAR easier. Less parts means less can go wrong, and there are less connections to corrode and give you issues later.

 

[Worlddre 5,000+ posts]

IIRC this is gonna take 3 relays, one to the fog lights and one to the headlights and one that will trigger between the fog lights and headlights.

Not necessarily...most aftermrket foglight sets come with a relay to drive...wire the fog lights so that relay is triggered by the parking lights and use a separate relay to break that connection triggered by the headlights.

 

[bubbagumper6 5,000+ posts]

Not complicated, not a headache, and not going to fail. If you make your connections secure these relays should last the life of the car (I've never had one fail).

Also, yes you should only need 2 relays, one to make the connection when the parking lights are on and one to break it when the headlights are on.

EDIT: They will need to be 5 pin relays though! Radioshack only sells 4 pin relays (and you'll pay like $8 each), get them from here: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=330-073

 

[Tj B]

All you need is a single relay but it's going to depend if your parking lights are a negative or positive trigger.

If they are positive, the relay would be wired like this -

85 - parking light wire

86 - ground

87 - fog light 12v wire

30 - constant 12v fused

And then you would just ground the fog lights. If your car had a negative trigger for parking lights onstead 85 would be 12v constant and 86 would go to the parking light wire.

 

[mat3833 10+ year member]

just get a tripple pole, dual throw relay..... wire the main to the fogs. then the secondary to one of the suply wires for the runnign lights. then when you turn the running lights on, the fogs come on. then wire the main headlights to the third pole. when you turn them on power is removed from fogs. its quite simple actually.

oh, and i might have fudged the name of the relay up. but it has one power side and two neutral sides. basicly you can use 2 power sources to turn on of off the power side.

Matt

 

---------- Post added at 11:05 AM ---------- Previous post was at 11:04 AM ----------

 

oh yea, or do what the guy above me said.... he actually has the numbers and all. **** you TJ.....

Matt

 

[bubbagumper6 5,000+ posts]

All you need is a single relay but it's going to depend if your parking lights are a negative or positive trigger.
If they are positive, the relay would be wired like this -

85 - parking light wire

86 - ground

87 - fog light 12v wire

30 - constant 12v fused

And then you would just ground the fog lights. If your car had a negative trigger for parking lights onstead 85 would be 12v constant and 86 would go to the parking light wire.

How does your setup turn them off when the headlights are on?

 

[12voltz+- 10+ year member]

Give that a go

 

[mendon99 10+ year member]

should be able to do with just 1 relay

85: ground

86: head light +

87a: parking light +

30: out to fog light +

only works with pos park and head lights

 

[bubbagumper6 5,000+ posts]

should be able to do with just 1 relay
85: ground

86: head light +

87a: parking light +

30: out to fog light +

only works with pos park and head lights

The problem with that is your drawing the power for the fog lights from the parking light's power. Could be enough to pop the fuse, it would be better to run a second relay so you can use a dedicated 12V line. Kickerassman's diagram looks correct.

 

[12voltz+- 10+ year member]

exactly ^ thats why u want to use to use the parking light + as a trigger for the 1st relay to send power to the 2ndon 87

 

[mendon99 10+ year member]

Might draw too much, might not. Worth a shot

 

[bubbagumper6 5,000+ posts]

Might draw too much, might not. Worth a shot

For an extra $1.79 he can have a dedicated power line which will be much more reliable...not worth a shot