Brakes are Only Applied to Trailer When Manual Override Switch is Being Used on a 2003 Ram 2500

Question:

I recently changed the brake switch on my 2003 Ram 2500 and noticed when hooked to our 5th wheel, the lever activates the trailer brakes, but the pedal does not. Display shows .c. indicating boost active, but does not read voltage when pedal is depressed and its not stopping well. I purchased the new light switch from Autozone and it works with a short delay in illumination after pedal is depressed. Before I tap into wiring and go buy a new switch, I wanted to get an opinion if this has been and issue.

asked by: Brad

Helpful Expert Reply:

Before you get a new stop light switch, I would try testing the red wire that is connected to the back of your Prodigy P2 # 90885 with a Circuit Tester # PTW2992. You shouldn't get a signal until the brake pedal is pressed.

If you do not get a signal, then you will want to test the OEM wiring for the stop light switch. If that is working just fine, then you will just need to replace the wire from your P2 to the OEM wiring on your 2003 Ram 2500. For a plug-in adapter use part # 3020-P, but if you have the pigtail, you will want part # 20127 instead.

Since the P2 pulls power from the battery it makes sense that if the red wire is damaged that you are still able to apply the brakes with the manual override lever.

You can also check your CHMSL (Center High Mount Stop Light) fuse to see if that needs to be replaced.

If you are getting no signal on that red wire or the OEM stop light switch wire then you will need to either replace your stop light switch or take your Ram to a shop and have them take a look at it.