On our 2004 Express 3500 (Class B Motorhome conversion), the Stop Lamp fuse in the engine compartment (#7 fuse, 15A, labeled STOP LP) fuse box blows intermittently after replacement. This causes all of the brake lights to quit working (including the high 3rd stop light). No other fuses seem to be involved, and I checked them all, in both fuse box locations.

I have completely disconnected the trailer wiring harness, which was plugged inline with the rear driver's side lights. The fuse still blew. The trailer plug was looking a little shady corrosion-wise, and I am going to replace it, so I was hoping that was the problem. It's not.

I took apart all 3 taillight assemblies to inspect the sockets and bulbs. They all look good, and all the rear lights seem to work perfectly for a while after replacing the fuse. Then sometime later after driving I realize the brake lights are out again. It seems to happen with just a day or two of driving the van either running local errands or on highway driving.

I have not determined a pattern yet as to when the fuse blows, or why, or what else might be going on when it does, and have not caught it in the act. I have tested it with engine running and without when sitting in the driveway after a fuse replacement and I can't get it to blow right away.

Unfortunately without a way to monitor the brake lights from inside this is a hard one to figure out. I may need to hack together some trailer lights inside to monitor what is going on.


So does anyone have any suggestions about what else I can check or what might be going on here? Are there any electrical manuals or diagrams floating around for this year or similar years (some pretty exhaustive google searches have pulled up NILL)? I'm a good electrical troubleshooter in general, and work in a technical field (not automotive though), but when all the wiring is hidden away and the problem is intermittent, this really gets frustrating.

Thanks!

Anne.

 

Strange. Are you sure that one of the bulbs has not broke off inside and the 2 filaments are touching? 1157 bulbs have the tail and stop light filaments inside....
If you have changed the bulbs try that. Maybe even switch to led bulbs to see if less current draw helps. You may have a bad ground somewhere, or corrosion on the contact points.
On the sockets, where the wires go in, there is a contact soldered to the end of the wire and it goes inside the socket and touches the metal part inside. My backup lights corroded inside the socket where you cannot see. I popped off the retainer clip and pulled the sores out and cleand up everything and added contact grease. Works now.

 

Thanks for the suggestions.

I will triple check the bulbs and the sockets. I can't quite visualize what you are saying with how the sockets are constructed, but I will look at it, take apart anything I can for a cleaning, and try some contact grease.

I already had the idea of trying LED bulbs for the current draw issue. Does anyone have any preferences about a good drop-in replacement bulb - preferably one I can pick up locally at one of the big chain parts stores? Are they all about the same nowadays?

I don't think the 2004 Express uses 1157 bulbs for the stop/turn. What I pulled out were NOT the twist style BA15D bases. It was a wedge base. I will have to look these numbers up - the 3rd high brake light also has a different kind of bulb. Hopefully they make an LED for that...

 

Looked it up - 2004 Express 3500 brake lamps are the 3157 and the high stop lamps are 912.

 

Check the wring around the brake pedal to make sure its not shoring out around the brake switch...