Towing Relays | Fog cut-out Relays | Details
These relays are designed to switch off the foglamp(s) of a towing vehicle when the foglamp of a towed trailer is on.
The reason for turning off the vehicle foglamp is to avoid a distracting glare being reflected by the towed trailer, especially if the trailer is a caravan.
A fog cut-out relay is, in fact, a combined monitor and relay: the relay that switches off the towing vehicle's foglamp is switched by a monitoring circuit that operates when it detects current flowing through it to the trailer foglamp.
The switched side is fitted in line in the vehicle foglamp circuit and the monitoring side is fitted in the cable going to pin 2 of the vehicle's trailer socket.
It is necessary before fitting to cut the wire that supplies the vehicle foglamp.
See Fog Cut-out for full range of relays and fitting details.