The ERICH JAEGER Trailer Testing Unit - Functional range

ERICH JAEGER is a specialist for retrofitting wire harnesses for trailer operation. The company offers quick installation solutions and assistance with the activation.

After installation with all electrical connections to the vehicle electrical system and the trailer control unit, ERICH JAEGER recommends a final function check. After all, an error in the end consumers' vehicle display or the reclamation of a flashing brake light has to be prevented - because this is when the nerve-racking troubleshooting begins.

With the ERICH JAEGER trailer testing units, specialist workshops can check the correct installation of a wire harness before handing over the vehicle to the customer. In this way, there are no bad surprises when the towing vehicle ist connected to the trailer - and depending on the type of testing unit, users also have the possibility to check the ligting system of a trailer, for example when converting to LED lights, repairing the wiring or replacing the plug.

Prerequisite for different systems

In practice, a 13-pin trailer socket according to ISO 11446 is usually retrofitted - this corresponds to the current state of the art and enables the connection of modern trailers. However, older 7-pin systems according to ISO 1724 are also used when it comes to the operation of simple load trailers.

The systems place different demands on a trailer tester: While only 6 different lighting functions are tested with a 7-pin electrical installation kit, the 13-pin system adds the function of the reversing light and two separate power supply circuits.

Both configurations can be tested quickly and easily with the compact ERICH JAEGER automotive testing unit.

 Contact no.FunctionCross-sectional areaCore insulation color
1Left-hand direction indicator light1,5 mm²yellow
2Rear fog light1,5 mm²blue
3Common return for contacts no. 1 to 82,5 mm²white
4Right-hand direction indicator light1,5 mm²green
5Right-hand rear, position and marker lights
and license plate lamp
1,5 mm²brown
6Brake lights1,5 mm²red
7Left-hand rear, position and marker lights
and license plate lamp
1,5 mm²black
8Reversing light1,5 mm²pink
9Power supply (steady, constant)2,5 mm²orange
10Power supply controlled by ignition switch2,5 mm²grey
11Common return for contact no. 102,5 mm²white/black
12Reserved for future allocation---no core
13Common return for contact no. 92,5 mm²white/red
 Contact no.FunctionCross-sectional areaCore insulation colorDesignation according to DIN 72552
1Left-hand direction indicator light1,5 mm²yellowL
2Rear fog light1,5 mm²blue54g
3Common return2,5 mm²white31
4Right-hand direction indicator light1,5 mm²greenR
5Right-hand rear, marker, position light and license plate lamp1,5 mm²brown58R
6Brake lights1,5 mm²red54
7Left-hand rear, marker, position light and license plate lamp1,5 mm²black58L

Different types of Testing Units

The new trailer tester from ERICH JAEGER features a dual function. On the one hand, a function test can be carried out to check the correct assignment after installing an electrical kit in the towing vehicle. On the other hand, the correct installation of the lighting on the trailer can be checked (e.g. when converting to LED lights, repairing the wiring or replacing the plug).

When checking the towing vehicle, the user can select the light function to be tested using the controls in the vehicle. It is also possible to simulate a defective blinker light with two switches in the tester.

Users can select the light functions of the trailer using a controller in the user interface of the tester (+ separate power supply). The test can be carried out by one person thanks to a 5 m long connection cable.

Further Information

The trailer testing unit by ERICH JAEGER simulates the functionalities of a trailer by triggering the lighting signals of the towing vehicle. Via the lighting controls in the vehicle, users can choose the functionalities to be tested. Moreover, two switches in the testing unit‘s operating panel enable them to simulate a failure of the direction indicator lamps. Testing can be carried out by one person from the driver´s seat with a connection cable of a length of 5 m (16.4 ft).

Further Information

Use and operation

Step 1 - Connecting the testing unit to the vehicle

  • Remove the testing unit from the workshop shelf and establish the 13-pin connection to the vehicle via the 5m cable line
  • Use enclosed adapter with the 7-pin socket on the vehicle

Step 2 - Checking the light functions and the charging line

  • Switch on the desired light function in the vehicle
  • On the tetsing unit, the corresponding light function marked with a symbol and the bulb of the trailer lighting illuminate
  • When the continuous positive charging line is connected, the corresponding LED on the test case lights up
  • When the switched charging line is connected, the corresponding LED lights up when the ignition is switched on

Step 3 - Checking the turn signal function

  • Switch on left turn signal
  • Flip the "L" switch and check the corresponding error message for the legal requirement* of the trailer indicator check

  • Perform the same test for the right side

Testing Unit - Video

The operation of the trailer testing unit is therefore very simple. For better comprehensibility, ERICH JAEGER also provides an instruction video and operating instructions.

*Legal requirement
The function of the blinker lights on the trailer is the only function whose display must be monitored. In the event of failure of the trailer blinker light, this error must be indicated to the vehicle driver, for example by the double flashing frequency of the blinker control light in the cockpit.

FAQs - Use of the trailer testing unit

For whom is the product suitable?

The trailer testing unit is a must-have for all workshops that offer electric installation kits for retrofitting the trailer coupling. Furthermore, the purchase is recommended for small workshops that perform repairs on the trailer wiring or trailer socket.

What can the trailer testing unit do?

The ERICH JAEGER trailer testing unit quickly and reliably checks the correct functionality of the electrical wiring and trailer control electronics on the towing vehicle and the trailer.

What can't the trailer testing unit do?

The trailer tester cannot correct the error itself. But it reliably displays any possible error and saves valuable time during troubleshooting.

How does the ERICH JAEGER solution differ from other competitive products?

The testing unit simulates the complete electrical system of a trailer. The loads with 21 watts and 10 watts correspond to the loads of a usual trailer lighting. ERICH JAEGER has deliberately dispensed with additional, unnecessary and expensive technology such as radio transmission: The robust solution with a 5m cable enables a simple function check, which can be carried out by only one person. In addition, it is immediately ready for use and easy to use.

In comparison, commercially available smaller test plugs for the trailer socket do not simulate the usual trailer loads and therefore do not offer the complete range of functions.

ERICH JAEGER thus has a robust, reliable and at the same time inexpensive service solution for small and large workshops in its range.

Technical data

Performance features

Nominal voltage:12V
Contact:13-pin plug for 13-pin vehicle socket according to ISO 11446
Adapter:13P/7P-adapter for 7-pin vehicle socket according to ISO 1724
Cable length:5m
Outer size in cm:39/15/31 (L/H/W)
Weight:3,25 kg

Light bulb 21 W (brake, indicator, reverse light, fog light)
Light bulb 10 W (rear light)

All bulbs individually replaceable


Scope of supply

  • Automotive testing unit in robust, double-walled workshop test case
  • Cable with 5 m length and 13-pin ERICH JAEGER plug
  • Adapter from 13-pin to 7-pin plug
  • Self-explanatory manual with pictograms in 25 languages

The ERICH JAEGER Testing Unit - Conclusion

With the testing unit for trailer simulation, ERICH JAEGER offers a robust, compact and inexpensive service tool for the technical inspection of the trailer interface. A must-have for all professional workshops offering retrofitting of a trailer coupling and for ambitious campers who want to play it safe.