12V Relay and Diode Help

[AirControl]

I retrofitted my truck with hid projector lights that are controlled off aftermarket relay harnesses. Those relays are activated by the oem signal that used to plug into the halogen bulbs. When I turn on my high beams it cuts power to my fog lights. I would like to have my fog lights come on when I turn on my high beams. I would like to run a wire from the high beam signal to the relay coil of the fog lights and put in a diode in series. That way only the high beams activate the fog lights and the fog lights can't turn on my high beams. However, I am unfamiliar with diodes and am unsure which to use. Can anyone help me select a diode for this?

Also, I had a shop install a security alarm in my truck after someone broke into it. However, they tied a relay coil into my interior dome lights (not sure what it actually controls) and every time my inter lights dim the relay chatters like crazy. How can I stop this?

Any help would be greatly appreciated, thanks

 

[Dragon Tamer]

What is most likely happening with the fog lights is that when they build the truck, they assum that you are not going to be using the high beams while there is fog outside. So if you turn on the high beams it disengages the relay for the fog lights. I recently did this to my car and the way that they did it was that the switch for the high beams was a normaly closed switch so that once it opened when the high beams were on, it simply opened the circuit. All I had to do was cut the wire that ran to the high beams and connect the the lead of the relay to ground. This may be different for your truck though so only you will be able to tell what is going on.

As for the "chattering" relay, it sounds as though they are trying to use PWM to dim the lights. This is a crapy way of dimming a light since the relay will wear out much sooner than intended. Relays were not intended to operate at such frequencies. I would recomend finding that relay and either removing it or bypassing it some how. If you still want the dimming lights than try removing the relay and replacing it with a power MOSFET or power transistor of some sort. This will last longer and will actually work while the security system is trying to dim the lights with PWM. You could even connect the lights right back to the terminal that they used to be connected to.