Towing Relays | Bulb-failure Bypass Relays | Details
Trouble-free fitting
These devices allow trouble-free fitting on vehicles with complex electrics and electronics. They are designed to operate trailer road lamps in unison with the towing vehicle's road lamps without drawing any significant current from the vehicle's road lamp circuits. They are used in vehicles that have bulb-failure warning devices that would be activated by the simple connection of additional lamp circuits for the trailer directly to the vehicle's own lamp circuits.
Not detected
Bypass relays employ miniature relays to switch the trailer lamps on and off. Connection is made to the vehicle's lamp circuits but only for the purpose of energising the coils of the relays. The current drawn by each relay is less than 40 milliamps (0.04amps). This current is so small that it can be drawn from the vehicle's lamp circuits without bulb-failure warning devices in the vehicle detecting its loss because the normal tolerances found in typical vehicle lighting circuits are greater than 0.04 amps. (The latest 7-way bypass relays [TF2217 and TF2217U] draw less than one milliAmp)
Power direct from the battery
Power for the trailer lamps is taken directly from the vehicle's battery and merely switched by these relays. No significant load is put on the vehicle's own lamp circuits.
Easily handle currents
Although the coil currents are tiny, the switching capacity of each relay is 10 amps. This means they can easily handle the currents found in typical trailer/caravan road light systems.
See Bulb-failure bypass for full range of relays and fitting details.