Troubleshooting Curt C56175 4-Pole Trailer Wiring Harness Installation on 1990 Mazda MPV Van

Updated 07/19/2016 | Published 07/18/2016

Products Featured in This Question

Curt Tail Light Converter with 4-Way Flat Trailer Connector

(367)

$28.94

Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector

(1909)

$87.94

Hook Probe Circuit Tester

(66)

$14.36

Question:

Would like to know if the curtis #C56175 is the right one for my MAZDA MPV VAN 1990, I was told that it was but these vehicles either come w/standard or other type of lights mind uses standard bulb system and not the other type of lights neon. the lights dont still work right even w.\/this converter and all the wiring on both the vehicle and the trailer are showing they are properly wired correct so it must be a bad converter or the wrong on? I feel that Ive been misled because I still have no trailer lights? or b rakes and ht e trailer has more grounds then the empire state building!

asked by: Harry J

Helpful Expert Reply:

There are two Curt 4-pole wiring harness fits for your 1990 Mazda MPV Van, the part # C56175 that you purchased (thank you) and the powered-type unit # C59236 which can deliver higher current output of 5- and 7.5-amps per circuit. Harness # C56175 is not recommended for use with cars that have LED-type lighting because such high-efficiency lights use much lighter-gauge wiring and this light wiring can sometimes prevent enough current from flowing to the trailer lights.

The powered harness # C59236 avoids this issue by drawing the actual power for the trailer lights directly from the car's battery, NOT through the car's internal wiring. The signal wiring is used only to switch the unit on and off, but the actual power that lights up the trailer lights comes from the black power wire that connects between the battery and harness through an included fuse holder.

One likely cause for the problem you are having, other than an insufficient ground, is that the trailer lights' total power draw exceeds what the vehicle wiring and harness can deliver. Another possibility is that the harness is bad.

You can test the harness using a circuit tester like # PTW2993 to find out if the problem is in the vehicle wiring or the harness. Apply the tester to the wires entering the left side of the converter. These are the input wires. Test them one by one to see if the correct signals from the car are reaching the converter. If yes, then test the output side. If signals are going in but not coming out, then the unit is bad, and it should be replaced. If no signals are reaching the converter, then the issue is upstream in the vehicle wiring.