Trailer brake controller - Reading short when fine?

[RPS13]

4th gen 4Runner. 2007, has the connector under the dash and the 7 pin connector out back.

I put a Prodigy P3 controller on with the plug and play harness. Towed fine on my trailer. It rained for 2 days straight while I was at the track, and I plugged the trailer in and the controller reads out "short to ground, no trailer brake output." This happens even with the trailer NOT connector to the 4Runner.

I've checked with two multimeters, there is NO continuity between the yellow wire on the under dash connector (which goes to the trailer brakes) and ground. There is good ground continuity on the connector (brown wire), and 12.7V with the 4Runner off on the black wire I thnk it is (the other larger 14-12 Ga wire).

Both fuses associated with trailer brakes and tow package (I think that's what it's labeled in the underhood fuse box) are fine.

So my question is, there is NOT continuity to ground on the trailer brake wire, but the controller keeps reading it as such. Is there anything I can check next? Is this a common problem?

I'm a little stumped, and don't know why it worked fine for 2+ hrs, then messed up. The brake controller is brand new.

 

[ebg18t]

That is really odd. I would check the connectors and maybe try some dielectric grease on the connections. Maybe it is just a bad connection that needs some help.

 

[RPS13]

Checked through everything again. Still no continuity from trailer brake output to ground, reading 12.6x V with the key on, engine off on the 12V line. Ground has continuity, and the plug and play harness has another ground that I put on a dash bolt that went to the steel dash bar (verified ground continuity there too, as you'd expect it would have).


I'm really stumped, and I don't know WTF is going on...


The good news is the trailer at ~4100-4200 lbs actually tows fine without brakes on it. The brakes make it better of course, but I never felt it was dangerous on a 1.5 hr tow home.

But I'd really like to get them fixed, and I'm honestly stumped.

 

[gm350reratliff]

I guessing there is water inside of the 7-way plug where the vehicle harness plugs in. It doesn't take very much to cause that. I would unplug the connector, remove the 7-way plug from the vehicle, clean them both with contact cleaner (completely clean/remove any corrosion that has started), when completely dry liberally apply dielectric grease, re-install plug and plug in connector.

 

[RPS13]

On the 4Runner? It's a weatherproof connector with individual seals on each wire, like you typically find in an engine bay. I didn't disassemble that part of the connector, but I can't see how they'd leak.

I'll check it out, but the stock connector is definitely weatherproof.

 

[RPS13]

BTW - for anybody who brings this up in a search, the Prodigy P3 had an internal short. I isolated the blue output wire (pulled from brake controller connector), and it was still throwing the "shorted output" error.

Tekonsha tech support was really easy to work with, I just sent in some info and the controller and had a new one in about 1.5 weeks.

I did buy a cheap $30 Tekonsha POD controller (time delay, not proportional), which worked fine. Honestly, in flat towing I didn't notice a huge difference other than it's a balancing act of how much you want the trailer brakes to help, to the point that they probably aren't doing much on a hard stop if you set them up to work smoothly for normal stops. Backing up with the POD really sucked though, so that made me glad to have the Prodigy back.

The 4Runner has been towing the trailer and car just fine. It is a bit sluggish when heading up an on-ramp without a merge, but I can't see a V8 helping there much, as to really not have an issue on accel it'd need to have Tundra-like power. Gets about 13-15 mpg towing (trailer + car is probably around 4100-4400 lbs, another 200 lbs of cargo in the 4Runner, weight dist. hitch), so that's not bad. I keep it in 4th 95% of the time, as there are some hills just north of me.