Lights problem

[Chuck.C]

All of a sudden my trailer lights won't work correctly. Checking the output from the RV (both using a multimeter and a separate light set) shows the stop and blinkers not working (both sides), but the running lights are fine.
I've checked the fuses on the firewall, and swapped relays to no avail. The fact that parking lights work proves it's not a ground problem.
When the meter is looking at the stop or left/right circuits, there's a VERY small voltage indication.
Anyone have any idea of where else to look?

[Falconer]

Kinda general as there isn't much vehicle-specific info provided, but start with working backward from the connector. Very little voltage at the brake terminal? OK, do the TV brake lights work? If so, follow the wiring back to where the trailer plug picks up its brake light feed.
On some vehicles that will be at or near the tail lights; in others it will be up under the dash. Or maybe there's a relay.
Do you have a wiring diagram? If so, read it and determine where you could get good TV lights and not trailer.
Might be worth a good look at the plug on the TV and trailer; common spot for corrosion to build up...

Charlie

[Flybob]

Not sure on your specific model, but many times trailer lights are on a separate fuse from the MH lights.

[Chuck.C]

The RV lights work fine, and the output of the trailer connector is where there is no (nearly) output. Except for the parking lights, which work fine.
The vehicle has a Ford F-53 chassis.
As stated before, I checked all the fuses on the firewall, and swapped a couple relays (TV with Trailer turn signal) with no help. No sign of corrosion on the connector.
Strange that both turn signals and brake lights quit at the same time. I'm hoping someone out there has had a similar problem and knows of another place to look.

[TitanMike]

I can't speak directly to the F-53 chassis but every Ford I've owned that was factory wired for trailer power used relays on the stop/turn "circuit". I'd check to see if there are relays in this circuit and since both left and right are not working it's most likely that it's not bad relays but one of the connections they have in common like the main power feed or ground.

Something to investigate.

Just a thought but check to see if the fuse or fusible link for the 12V charge line in the trailer connector is still good. This may be the power feed to the relays that supplies the power used for stop/turn lights. On a trailer wiring system that uses relays like described, the regular stop/turn light power merely controls the relays that in turn switch on and off the trailer stop/turn signal lights using power directly from the battery. This is done so flash rates don't change when trailer is hooked up. Also prevents overload of flasher and smaller wires in main vehicle from being overloaded by larger (or multiple) lights used on some trailers.

[bubbles]

Fuses 1 and 9 plus relays 1 and 2 should be checked at the fuse panel inside the MH just to the left of the steering column on the vertical carpeted firewall.

[Chuck.C]

Thanks, TitanMike. I'll see if I can find a fuse/link in the feed to the relays. That could explain why both legs failed at once but the running lights are ok.

[Chuck.C]

After looking all over for a box that converts separate stop/tail and turn lights into combined, I gave up and added an aftermarket converter, tapping into the RV's light leads. Seems to work fine. A problem came up with trying to remove the RV lights to get to the wires - the idiots who installed them made the holes a tiny bit too small, then forced the old lights in, which made it impossible to remove them without messing them up. Good excuse to switch to new LED lights. Still had to slightly enlarge the holes to fit them in.
Thanks for everyone's help.