Wizard Imports Limited

Towbar Relays


Wizard Imports Limited




TEB7A-24 fitting instructions
How to fit unit
TEB7A-24 fitting instructions.pdf (133.2KB)
TEB7A-24 fitting instructions
How to fit unit
TEB7A-24 fitting instructions.pdf (133.2KB)

TEB7A-24       7 Way Bypass Relay

This 7 way bypass relay may be used on 24v negative earth vehicles which require a bypass relay to be fitted for circuit protection or to avoid confusing the bulb failure warning systems when towing a 12v trailer or caravan. 


Main Features

7 way bypass relay with 7 terminal outputs arranged in 12N sequence including reverse.

 Statutory sensing of trailer  flasher function without the normal voltage drop avoiding potential dimming of flasher bulbs.

 All circuits fully snubbed for EMC protection.



Normal rules of competency apply to anyone fitting this relay to a vehicle.

It should be fitted to negative earth vehicles only.

Great care should be taken if the relay is fitted to a vehicle having multiplexed circuitry, and no attempt should be made to interrupt or interfere with the BUS, the ESUs or the power cable of a multiplexed system. Power sources should be taken from the main fuse box or battery and signal sources from the regular 24v system directly feeding the various rear road lamps.



Fit 12N socket and cable according to instructions supplied with the socket kit.

Fit 12S socket and cable where required (i.e. if reverse light is to be attached) according to instructions supplied with 12S socket.

Route 28/0.3 cable (2.0 sq mm) from car battery centre  post (i.e. 12v tapping) to boot or fuse box, fitting an inline 15a blade  type fuseholder, but removing the fuse at this stage.  Alternatively a 24v – 12v Switch Mode  Converter may be used to generate the 12v output to the trailer.

Offer up the relay to the above cable clusters and make secure connections through the terminal blocks on the relay according to  the chart Below.



Relay Terminal



Connection to Relay



28/0.3   (2.0 Sq mm) cable from car battery 12v centre post


Do   not make any connection if relays’ buzzer is to be used.

Otherwise   connect to panel lamp on console via light signal wire and then from the   panel lamp to earth.


12N   Cable.   Yellow Lead


   “         “         Blue Lead


   “         “         Green lead


   “         “         Brown lead


   “         “         Red Lead


   “         “         Black Lead


12S   Cable.    Yellow Lead


Using scotch locks, solder joints or similar, attach the various leads coming from the underside of the relay to the car loom, teeing in at a point close to the car lamp circuit that is being sampled and avoiding any multiplex wiring or other devices.


 Signal Wire                                                                                          Connection to Vehicle Loom


Near Side Flasher


Fog Lamp


Off Side Flasher


Off Side Tail Lamp


Brake Lamp


Near Side Tail Lamp


Reverse Lamp


Secure firmly to vehicle chassis via   ring terminal


 Secure the relay to the harness or similar preferably using a tywrap,

 Insert the inline fuse and test.  If a test board is used, it should have 21w bulbs on the flasher circuits as the buzzer only works under load conditions.