Relay Guide | Bypass Relay Checklist
The following checks will tell you which bypass relays to use.
1. Check the vehicle's display to see if it detects the removal of bulbs. If a fault shows on the vehicle's display when you remove a bulb, you need a relay
2. Check the fuses AND wire sizes in the vehicle loom to see whether additional current can safely be carried to supply the trailer road lamps directly. (Determine wire capacities by counting the strands, not by looking at the apparent wire thickness. Thinwall cables may look thinner but have higher capacities than previous "conventional" cables. (See cable chart.) If you are in any doubt, you are probably wise to fit a bypass relay
Once you have identified which circuits need bypass relays, use the checklist below.
Reversing Lamps: Capacity built into the seven way relays
| Vehicle Circuit | Relay |
|---|---|
| Stop lights only (Single) | TF1011 |
| Tail lights only (Double) | TF1013 |
| Flashers only (Bypass Relay) | TF110R |
| Stop lamps and Tail lamps (3 lamp) | TF1013 |
| Stop and Tail and Fog (4 lamp) | TF1014 |
| All lamps (Universal) | TF2217LOGIC a& TF2218 |
| Fog lamp only | TF1011 |
| If you decide to cut out the vehicle's foglamp when towing, use one of the following: | |
| Fog cut-out (Single) | TFC1 |
| Fog cut-out (Twin) | TFC2 |