Electrical 91 Daytime Running Lights Troubleshooting

[Elkennetho]

Hi all,

I have a 91 5.0 coupe with daytime running lights (Canadian model) that I am trying to diagnose and fix. Following some common troubleshooting tips I replaced the DRL module with this part from Rockauto:

More Information for STANDARD MOTOR PRODUCTS LMD100

The DRLs worked for about a minute. After cycling the headlight switch and park brake, they no longer worked. No combination of ignition, headlight and park brake switches gets them to turn on anymore.

Does anyone have any tips for troubleshooting? Assuming that the brand new module is not defective, perhaps there is a wiring fault or short somewhere?

Thanks!
Ken

 

[90sickfox]

Check all of the connectors for loose wires. Headlight, multifunction, and ignition switch are common to have issues. You need to find what hot wire goes to the DRL and trave it.

 

[Elkennetho]

That makes sense. I'm still searching for a wiring diagram. Would you leave the battery connected while probing to see the "hot", or switch on wires?

 

[90sickfox]

Battery connected.