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General 

This tester has one side to connect the 7 or 13-pins plug of a trailer and another side to connect the 7 
or 13-pins socket of a car. This tester indicates quickly if a failure concerns the wiring of the car or the 
wiring of the trailer.  

 

CAUTION:

 Only use the tester at 12V Systems. 

Higher voltages can cause damage to the tester or the car electrical systems. 

 

How to test the connection of a 

Trailer

 (can also be a caravan or bicycle carrier) 

1. 

Put the plug in the connection of the tester.  

2. 

Press the yellow button on the side of the tester. 

3. 

If the wiring is good, all the LEDs light up.  

 

The function of each LED is (acc .Iso 1724): 

A. 

left hand indicator (yellow) 

B. 

foglight or 12V (blue) 

C. 

right hand indicator (green) 

D. 

right rearlight (brown) 

E. 

brake light (red) 

F. 

left rearlight (black) 

G. 

mass (white) 

 

Attention:

 The pin 

B

 at 7-pins connector can be used either for a warning foglight or a permanent 12 

V connection. 

 

4. 

If a LED doesn't light up, it is because the corresponding wire is defective.    

 

             

If all the LEDs don't light up. 

 

How to test the connection of a 

Car, camper 

1. 

Put the tester in the socket of the car.  

2. 

Press the yellow button on the side of the tester: 

3. 

If the wiring is good, all the LEDs light up. Do again steps 4 as previous. 

 

You can also test the functions of each pin of the socket. 

 

 

1. 

Switch on the left hand indicator (after switching on the ignation key). 

2. 

The corresponding LED must flash with the same frequency. If not, the left hand indicator wiring is 
defective / broken. 

3. 

Repeat steps 1 and 2 for the right hand indicator, rearlight, foglight and stoplights. 

 

Note:

 

With a 4 m extension cable, you can test the functions from the driver's seat more easily. 
See below the table for the potential problems: 
 

 

 

A

B

C

D

E

F

G

CT4691 

TRAILER / VEHICLE TESTER, 7 - PINS / 13 - PINS

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