Stumped, Relay to Switch Based on Power Source

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=146043
Printed Date: May 04, 2025 at 8:14 PM

Topic: Stumped, Relay to Switch Based on Power Source

Posted By: kwest944
Subject: Stumped, Relay to Switch Based on Power Source
Date Posted: February 26, 2020 at 5:37 PM

Am OK at normal relay stuff but stumped on this one.

Have a light bulb which is either:

A. On by way of dash switch
B. Off by way of dash switch

What I am needing is a way to connect relays where when turn signal is engaged it makes the bulb blink. Yes, the power when turn signal is engaged is from the turn signal relay in the car.

So, in scenarios above:

A. Turn signal is engaged, power from the dash switch is removed and the bulb blinks from power from turn signal relay
B. Turn signal is engaged, bulb blinks from power from turn signal relay

I have tried with two SPDT relays but in scenario A once the turn signal power is cut (blink off) it gets power from the dash switch so barely blinks at all...

Thoughts?

Replies:

Posted By: eguru
Date Posted: February 26, 2020 at 9:22 PM

Use Pulsed to Steady (Diagram 59) to provide a steady output from the flasher. Use that steady signal to drive the coil of a second relay that disconnects the light from the dash switch feed and connect it to the flasher signal.

Posted By: i am an idiot
Date Posted: February 27, 2020 at 5:08 AM

https://www.the12volt.com/relays/relaydiagrams.asp

Posted By: kwest944
Date Posted: February 27, 2020 at 9:30 AM

thanks.. part way there I think..

There are four different states:
1. Parking lights off, turn signal off
2. Parking lights off, turn signal on - Bubl blinks
3. Parking lights on, turn signal off
4. Parking lights on, turn signal on - bulb blinks, power cut from parking light switch

From your reply: "Use Pulsed to Steady (Diagram 59) to provide a steady output from the flasher. Use that steady signal to drive the coil of a second relay that disconnects the light from the dash switch feed and connect it to the flasher signal."

Like this?

posted_image

Posted By: kwest944
Date Posted: February 27, 2020 at 9:31 AM

forgot to ask, is the "fused 12v+" supposed to go to where?