The caps in post #19 are too small. The one in post #20 should be okay, depending upon the relay coil resistance.
The hold time is approximately equal to one RC time-constant.
Thus for a one-second blinker with 50% duty-cycle, the time constant of interest is 1/2 second.
For a 100Ω (estimated) coil resistance the required capacitance would be 0.5s / 100Ω = 5mf or 5,000μF.

As I said you likely need to experiment some to get the correct delay. You could use 2700μF caps and connect them in parallel to adjust the capacitance (the values add together in parallel).

Either diode is okay.

Here's a resistor assortment with that includes 1Ω

 

Not sure if it'll help but here's the dpdt relay I ordered.
(eBay) http://tinyurl.com/hbw4v93

So I can use the diodes I first posted? Just checking because I already have these.

These capacitors should be good then? Just add / remove to get the timing correct?
https://www.amazon.com/PANASONIC-EE...d=1474323392&sr=8-4&keywords=2700uf+capacitor

 

I can't access that eBay site. Does it state the coil resistance?
Those diodes should be fine.
Yes, those capacitors should be okay also.

 

Oh. That's cuz that was from my order page. Whoops. This should be the ad. http://m.ebay.com/itm/322111351577?_mwBanner=1

Looks like its less than or equal to 100 mΩ

 

Oh. That's cuz that was from my order page. Whoops. This should be the ad. http://m.ebay.com/itm/322111351577?_mwBanner=1

Looks like its less than or equal to 100 mΩ

No, that's the insulation resistance which should read 100Meg ohms.

The relay DC power is 1.2W at 12V (spec third line) which gives a coil resistance of 120Ω (P = V² / R) so you should be able to get by with a somewhat smaller capacitor than I calculated for 100Ω.

 

I've been trying to make something similar but what i have is a spot light with a running light connected in reverse polarity to the light (running light is a small led mounted inside the lens of the spotlight) i have two different power supplies. One is the running lights, the other is the spot light (just butt connected into the hot and the neutral on the other spotlights already there). When the running lights are on and i turn on the spot light i want the running lights to turn off until the the spot is swiched off. I drew up a diagram of how i think it would work but i may be wrong with how the coils are wired