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turn signals/fog lights

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=122032
Printed Date: July 09, 2025 at 7:44 PM


Topic: turn signals/fog lights

Posted By: fody55
Subject: turn signals/fog lights
Date Posted: May 27, 2010 at 9:28 PM

How would I hook up a relay for my foglights to blink with my turn signals?

When my fog lights are on, and my turn signal lights up, I would like the fog light to turn off and then turn back on at the same rate as the turn signal. Any idea how to set this up? Thanks.



Replies:

Posted By: oldspark
Date Posted: May 28, 2010 at 6:40 AM
Same as a combination brake-light & indicator or combine reverse-light & indicator.

Flashing the fog lights out of phase is simple - connect each side's fog light relay GND (#85) to the respective indicator's hot side.


In both cases, then await appropriate response from traffic authorities.




Posted By: anonymous1
Date Posted: May 28, 2010 at 9:21 AM
I think the problem here is that the fog lamps would already be on, so the matter would be interupting the normal switched path and making the fog lamp go off in sync with the turn signals.

-------------
I know just enough to be dangerous. VERY dangerous.




Posted By: oldspark
Date Posted: May 28, 2010 at 10:18 AM
Yes - in sync is the same as brake or reverse lights wit indicators coming on.
(IE - brake combined with indicators as per USA etc; reverse with indicators as per Japanese etc before reverse and indicators were separated.)
That's a nice little 2xDPDT relay switching arrangement.

The out-of-sync is simple - each side's fog-light-relay's coil is connected hot (#86) to fog-on (+12V) and their GNDs (#85) to each respective indicator lamp "hot" from the flasher can.   
So Fog-On means each relay earths through the indicator lamps, but if an indicator flashes on, the fog's #85 goes high & turns of that relay.
Use a series diode for each relay to prevent an on-indicator turning on the fog light (relays) IF there is a return GND path (which there probably isn't).


And I've probably just preached to the converted... (LOL!!!)
(Or LOL x 3, am I confused???)




Posted By: howie ll
Date Posted: May 28, 2010 at 5:05 PM
Converted straight to jail by Mr. Plod if that were tried here. (Even if they have it on their vehicles).




Posted By: oldspark
Date Posted: May 28, 2010 at 7:02 PM
But surely this is an offroad show car?

If not, I'd better delete my last reply pronto.
My first was bad enough, but at least carried
oldspark wrote:

... then await appropriate response from traffic authorities

(Or should I detail other immediate dangers?)





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