Electrical issue with trailer connected

TubaPete wrote:
My experience is that a poor ground can cause strange electrical situations,

I will support that.. IN my case no engine issues but the turn signals went very wonkey... First time I did not have a towed, turned out to be a bad contact (Bulb/socket not making good connection) on a front turn signal.. Removed and re-seated bulb, all good,

Next time was when we added the towed.. I upgraded the ground on the RV side of the connector.. problem vanished.

Grounds are a major pain in the fundement.

I have to ask do you have a battery in the trailer? And is it hooked up with the Negative terminal wire hooked up to the ground point on the frame of the trailer? Also is the battery fully charged? Good place to start looking first

I would check the CENTER unused pin on the trailer side. Make sure it is not connected to anything in the trailer or the tow truck. This pin is used for reverse lights if the trailer has them or an activation wire for a aftermarket part installed on the trailer, which you do not have. VERIFY that the GROUND pin on the truck side and trailer side is connected to a good ground. You cannot rely on the hitch ball to make a good ground connection. Doug

This happens when towing, all connections between truck and trailer are DC. Start by pulling the fuse that charges the battery from the tow vehicle. If some type of RFI is showing the vehicle a over or low voltage the computer can do all sorts or electrical switching to protect the vehicle. Hook up the trailer and see if a problem occurs while setting in the driveway. Activate each circuit one at a time looking for problems. Left turn, problem or not. Advance to right turn and so on. Brakes, backup lights, parking lights, turn signals with parking lights. Then move on to all of 12v fuses in the power distribution box.

Write down each result. If you find a problem keep checking to see if another circuit causes a problem. You may have to do a test drive and activate each circuit. If you don't find anything this way add back half of fuses and recheck. No problem add the rest back, at the point the problem shows back up just check each item individually that you last added, It's a process of elimination and it may take awhile to narrow it down. As stated before the battery acts to filter the circuits like a big capacitor. Once you narrow it down to which circuit is causing your problem then you have to check all of the connection and appliances on that circuit. It may be a ground, loose connection, bad component in a control board.

It won't be easy or quick. If your lucky and find the bad circuit on the first try, buy a lottery ticket. Good luck.

Not all trailers will have an OEM INVERTER installed. This is something the user adds to make 120VAC from the trailer 12VDC battery system.

It almost has to be some kind of RFI NOISE getting on your BATTERY CHARGE line between the Truck and the TRAILER. This would be the only WIRED CONNECTIONs between the Truck and Trailer. The connected batteries however on both ends really clean up things RFI wise...

POOR GROUNDS are another source of problems as well.

Here is a typical wiring BLOCK diagram for a 30AMP trailer system. Maybe will trip a thought or two...



Need to start tripping circuits I guess in an effort to pin-point source of problem. It will most likely totally amaze you when you find the source...

My 7-way cable terminates into an electrical box on the trailer side just under the trailer where the tongue frame is welded on and all of the trailer lights wiring etc is accomplished using large YELLOW twist-on connectors. The trailer wiring cable colors should be color for color connecting up the trailer side. Could be a easy place to have some frayed wiring or something like that touching something it shouldn't be touching...

got to start looking somewhere haha... All the information on this end is pure guessing...

Roy Ken

The biggest load would be trailer brakes- I would look at the brake controller.

Roy,
Trailer is stock and these issues only happen with this trailer. It has happened since the trailer was new. Thought the problem was with the first tow vehicle for the first year. Like I mentioned, it has happened on several tow vehicles as well, so this is pointing me towards the trailer. I am wondering about the charging system, as I know that the battery charges while driving. I will have to check on the INVERTER situation, but I know the fridge switches to propane when driving, but something else maybe running.

Thanks for the leads.

Have you added LED lights recently - Some of the LED BOARDS that have REGULATOR CHIPS on them will create alot of RFI SIGNALS that could possibly be getting into your truck's computer system???

It would seem to be a very unique electrical reason however to be back-feeding something back into the truck 12VDC system by just connecting up the 7-way trailer connector plug.

Almost have to fall back on something you may have added - maybe a large 4AWG battery cable to get the trailer batteries to charge better when connected to the truck system...

If this has just started to do this you need to think back to something new you may have perhaps done to the travel trailer???

The only thing the trailer connector does is provide 12VDC power for the trailer outside safety lights and electric brakes. It also sends a 12VDC charge connection to your trailer battery. These are the only OEM connections between your truck and trailer which makes it hard to imagine something is getting fed back into the truck computer system to change the parameters to your truck's performance package...

I would rule out something I have recently done first... My truck's 7-way connection is all protected by separate 12VDC fuses on each safety lights functions. Perhaps you can disable each leg one at a time feeding the trailer and see if you can pin-point which leg is getting the feed back into the computer system.

You sort have to rule out your trailer on-board converter/charger system having bad 12VDC regulation since it not 'ON' when being towed.

High wattage INVERTERs also put out alot of RFI signals if you perhaps have one of those running when being towed... Maybe powering up a fridge when being towed...

Just my thoughts

Roy Ken

I would start looking at the grounding of the tow and it's lights etc.

My experience is that a poor ground can cause strange electrical situations,