fogs on with parking lights and off w/ hb

Everyone I need to know how to wire a set of fog lights on with parking lights and off when high beam head lights are on. Its been along time since I've tried to wire dual 30 amp relays. I could use some help. Thanks

Bosch 30 amp relay

87

87A

86

85

30

Legally (at least here) they should only come on with the low beams but any way here goes. Relay 1. Pos output from switch to 87a. Pos from high beam to 86. Ground to 85. Output from 30. Relay 2 Output from 30 on relay 1 to 86. Ground to 85. Battery via a 20 amp fuse to 87. Lights out put from 30. You switch should be fed from a source that goes to pos when the side (parking) lights are on. Ideally I would use a third ignition controlled relay wired as such Switch output to 86. Ground to 85. Ignition to 30 and out put from 87. Wire this first in series with the original 1st. relay, this will prevent leaving the lights on with the ignition off. Up to you. Relays 1 and 2 need only be small 5 amp PCB types, half the price of regular relays as sold by DEI, R/Shack etc.

Sorry I forgot! Solder a 1N4004 diode between 85 and 86 one per relay with the bands towards 86.

Two relays? I was going to suggest wire the relay power as normal (fused +12V to 30 thru 87 to the (grounded) fog lights. Then coil 86 (on) to the fog light controller (on/off +12V switch whatever) and the coil ground (85) to the hibeam (ie, +12V when on) or whatever you want to turn the fogs off when also +12V. Plus a diode in the 85/86 line to prevent high beam on & "fog lights off" turning ON the fogs. (IE - Kathode - line end of diode towards 86 or away from 85.) Plus a suppression diode if required between 85&86 ONLY if the above reverse-polarity blocking diode has been fitted.

A much better idea Peter but I'd still add a second as an ignition (i.e.fail safe) interlock.

Good point. I was assuming the fog switch/controller itself to be IGN controlled. (And I'd consider the reverse-blocking diode to endure off with hibeam-only essential.) And on my 1965 vehicle I have a lights reminder ($1.30 plus 10-30 years LOL!) but I like lights independent of IGN. (Hence I can watch the girls thrashing to my stereo!)