Tow Wire Gremlins

[CVD]

I have a problem with my 2014 Honda CRV towing lights. Please bear with the long winded explanation (if it was simple I wouldn’t need help).

Background:
99 Itasca, towing 1) 2000 Wrangler, 2) 2014 CRV

Wrangler tow lights are via Wal-mart magnet lights, plugged into umbilical at tow bar. No problems (actually, minor question – at end)

CRV tow lights are via TrailerMate pre-built plug/play harness with diodes built in: http://www.etrailer.com/Tow-Bar-Wiring/TrailerMate/TM783120.html). Plugged into same umbilical as Wrangler. Running and brake lights are OK, problem with turn signal.

Problem – CRV hooked up, neither RV or CRV running:

RV key on, turn signal on (L or R). Problem: both L & R CRV signals flash, both RV signals flash. Turn signals aren’t useable.

I installed the harness about a year ago. Had problems with the CRV brake light fuse blowing, but thought I’d fixed it when I found a loose ground wire. I think the L & R turn signals worked properly then. This most recent trip (and turn signal problem) is only the 2’d time the CRV’s been towed. So, it’s possible I’ve had this problem since installing the harness.


Question - Could a bad diode in that harness cause this?

Note - Etrailer recommends a “brake light relay” kit, which is to isolate feedback from the towed vehicle braking signals to the towing vehicle. I don’t think lack of this is my problem, as I’m getting turn signal interference (towed brakes not active). https://www.etrailer.com/Tow-Bar-Braking-Systems/Roadmaster/RM-88400.html

Additional twist:
Because of this CRV turn signal problem, I looked closely at the Wrangler magnet tow lights. When the turn signal is on (L or R) and running lights are on, the “other” signal shows a very slight change of intensity with each flash. Not noticeable unless you look for it. I’m not too concerned about this.

I then go out my volt meter and measured output at the towing vehicle plug.
With running lights on: ground to running lights: ~12v (expected
Ground to Left light: .05 (not expected)
Ground to right light: .07 (not expected)

With brake lights on: ground to left and right: ~12v (expected)
Ground to running light: .05 (not expected)

Question – is this small (.05 or .07 ) voltage at the “off” connection something to be concerned with?

Suggestions appreciated,

[enblethen]

Look for the 3-2 converter on the back of the MH.
Sounds even more like either the ground or the unit has failed.

[CVD]

I checked the RV turn and stop lights, same light for both (bottom of the two, on each side). I also remembered that the TrailerMate CRV harness only utilizes one light bulb for S, T, & T; it does not use the amber light at all. So, I don’t think I have a 3 -2 or 2-3 conversion (combiner) issue. Agree?

Back to my original problem: I have an RV driven turn signal (L or R), going through the brake/turn light on the CRV and activating the lights on both sides of the CRV, and activating the lights on both sides of the RV. The diode isolates the signal as it goes into the CRV brake/turn light, but as it returns to CRV ground, could it go backwards through the CRV “other side” and back to the RV?. My head hurts trying to make sense of this, not sure it makes sense at all. Maybe I simply have a bad diode. I hate to start tearing the harness apart to test flow direction. Am open to suggestion.

One last observation/question. The TrailerMate harness grounds to the CRV. I was expecting the harness ground to utilize the white ground wire that returns to the RV and be completely isolated from the CRV. Seems to me that towed vehicle ground is unnecessary and opens up possibilities of interference like I’m getting. But it’s quite possible I’m missing something in this harness design. Thoughts?

[enblethen]

It is possible that the ground on the converter is not getting good connection.

[enblethen]

Check which lens lights for the stop lights.
Looks like the 3-2 combiner has failed, if the upper lens lights up for brakes.

[CVD]

The CRV has separate amber turn signals.

The RV has two red lights on each side in the back (pic below). I don’t remember if the stop and turn are separate, or if one is for running lights and the other is both stop and turn. In the pic, the lower light is “on”, which was a turn signal.

The tow plug at the RV bumper is round 6 pin (5 pins are “mapped” with a wire). I’m assuming 1 ground, 3 for STT, and 1 for an optional brake controller (which I don’t have). The other end of the umbilical is round 4 pin which connects to the 4 flat magnet light connector (Jeep) or the TrailerMate 4 round wire harness connector (CRV).

Thanks for the suggestions. I just put the RV away in storage, will go back to storage lot and confirm the stop/brake lights on the RV.

[enblethen]

If the MH has amber turn signals using a four wire OP needs one of these.
3-2 converter

[Horizon170]

You may need this.
Marvin
https://www.etrailer.com/Accessories-and-Parts/Tow-Ready/118158.html

[enblethen]

I believe your MH has amber turn signals.
Are your CRV lights for turn signals amber?
Are you using a seven conductor or four conductor umbilical cod/
It could be the taillight converter if using four wire.

[K_Charles]

The turn signal light bulb is the same as the brake light one some autos, not on others. If the Itasca has separate turn and brake lights then you need the isolated that trailer told you to get.

[Ductape]

Those little voltages don't mean much. Current flowing in a wire can induce current in adjacent wires, and a sensitive meter will show voltage traces if you just hold a lead in each hand- try it.

Bad diode in the CRV harness most likely.

The small variations in intensity of the tail lights when the turn signal is on is caused by the changing current in the ground wire. More current, more voltage drop in the ground wire, all lights dim slightly. Entirely normal, but if it's severe indicates a weak ground.