Brake issues and 12 v power issues

[Mark_TX]

We just purchased a 2019 Montana 3931 Legacy edition and having a couple of issues.

Tow vehicle is a 2015 GMC 2500 HD.

Issue one.......trailer brakes. When hooked up to RV and brake controller is set to anything above zero as soon as I touch the brake pedal is throws a fault and says Service trailer brake system. I feel the trailer brakes engage the 1st time I hit the brakes but then I loose all output from my brake controller. This also happens if I manually apply the brake controller on my dash. I can turn the truck off, open door, close door, start truck and it does the exact same thing....first braking you feel brakes and then fault.

I haven't experienced this isssue with my other utility trailers I pull with the same truck and the guy I bought it from didn't have any issues with his Ford F350 and RV.


2nd issue.........tow vehicle not charging RV battery while towing.

Is there a chance that the RV trailer plug is wired differently for a Ford vs GM?

It is freezing rain and 23 degrees in DFW this morning and I haven't had a chance to get out there with a volt meter to see if the truck is outputting 12v at the 7 way yet.

[travelin texans]

Most likely the fuse in the fuse box under the hood to the charge circuit is either blown or not installed. That would be the 1st check.
As for the brakes you definitely need those working towing a 16500lb GVWR 5er with a 3/4 ton any brand of truck!! Too much rv, too little truck!

[Mark_TX]

Originally Posted by travelin texans

Most likely the fuse in the fuse box under the hood to the charge circuit is either blown or not installed. That would be the 1st check.
As for the brakes you definitely need those working towing a 16500lb GVWR 5er with a 3/4 ton any brand of truck!! Too much rv, too little truck!

Ok Just went out there and in fact my 30amp fuse was blown. I am now wondering if there is a wiring issue on the RV plug.....maybe the 12v and the brake wires are flip flopped. I will have to check that.

Travelin Texans thank you for your feedback, but my truck is rated at 17,900lbs with a 5th wheel. Plus I have air bags to help level the load.

[jasin1]

Originally Posted by Mark_TX

Ok Just went out there and in fact my 30amp fuse was blown. I am now wondering if there is a wiring issue on the RV plug.....maybe the 12v and the brake wires are flip flopped. I will have to check that.

Travelin Texans thank you for your feedback, but my truck is rated at 17,900lbs with a 5th wheel. Plus I have air bags to help level the load.

Welcome to the forum. There was a post last year I think with same brand truck. There was a shorted wire in the trailer brake harness at or near the rv connector at the bumper of the truck

And the payload is what is critical on your truck…not the towing capacity ..that’s where you will probably fall short..I was and upgraded trucks…expensive lesson learned

[Mark_TX]

Originally Posted by jasin1

Welcome to the forum. There was a post last year I think with same brand truck. There was a shorted wire in the trailer brake harness at or near the rv connector at the bumper of the truck

And the payload is what is critical on your truck…not the towing capacity ..that’s where you will probably fall short..I was and upgraded trucks…expensive lesson learned

Thanks Jasin1 I will see if I can find that thread.

Payload capacity is bed capacity, correct? Why would that have anything to do with towing capacity? I understand that your suspension has to be able to handle the hitch weight, but when I hooked up to this trailer the seller was shocked that it only squatted a couple of inches and that was with the air bags at the minimum of 5lbs. He said his F350 single axle squatted alot more than my truck.

Just trying to understand.

We will be looking at 3500Hds but not a dually in the future. I have a hard time paying MSRP or above right now for a new truck, so I am hoping the bubble pops sooner than later and prices go back to normal.

[flybouy]

Originally Posted by Mark_TX

Ok Just went out there and in fact my 30amp fuse was blown. I am now wondering if there is a wiring issue on the RV plug.....maybe the 12v and the brake wires are flip flopped. I will have to check that.

Travelin Texans thank you for your feedback, but my truck is rated at 17,900lbs with a 5th wheel. Plus I have air bags to help level the load.

Ok, you are looking at a rating that may be true when towing a flat bed with a load over the trailer axles. Unfortunatly campers don't work that way Fith wheels have a pin weight that's about 23% of the trailers gross weight. So for that trailer you're likely looking at approximately 3,500 lbs. Then add another 200 lbs for a hitch and your PAYLOAD will be closing in on 4K and thats before you put anything orr anyone else in the truck.

I hate to be the bearer of bad news but that trailer is just to heavy for a 3/4 ton truck. Look at the sticker on the truck itself for your trucks rated payload.

[jasin1]

Originally Posted by Mark_TX

Thanks Jasin1 I will see if I can find that thread.

Payload capacity is bed capacity, correct? Why would that have anything to do with towing capacity? I understand that your suspension has to be able to handle the hitch weight, but when I hooked up to this trailer the seller was shocked that it only squatted a couple of inches and that was with the air bags at the minimum of 5lbs. He said his F350 single axle squatted alot more than my truck.

Just trying to understand.

We will be looking at 3500Hds but not a dually in the future. I have a hard time paying MSRP or above right now for a new truck, so I am hoping the bubble pops sooner than later and prices go back to normal.

The payload is how much you can put in the bed of the truck ( pin weight) it also includes everything else you put in the truck..others will chime in..just keep an open mind. Good luck and yeah it’s crazy times for truck sales and inventory

[travelin texans]

Originally Posted by Mark_TX

Ok Just went out there and in fact my 30amp fuse was blown. I am now wondering if there is a wiring issue on the RV plug.....maybe the 12v and the brake wires are flip flopped. I will have to check that.

Travelin Texans thank you for your feedback, but my truck is rated at 17,900lbs with a 5th wheel. Plus I have air bags to help level the load.

I will agree hole heartedly that your truck is rated to "tow" that much weight in the form of a gooseneck utility type trailer where the entire load is placed over the trailer axles thereby considerably lessening the pin weight,, this is how the manufacturer came up with that weight rating, not using rvs.
In the rv world that weight can not be moved around over the axles, therefore your concern is NOT how much it can "tow/pull", your truck can/will pull it all day & never break a sweat, but how much of that weight can it safely within the specs of your truck "carry" i.e. payload & axle weights?
The yellow/white tag on the driver's door jamb states "occupants & cargo must not exceed XXXXlbs", that's the payload for that truck. That includes, in your case, over 3500lbs of pin weight (23% of the GVWR) + the weight of the hitch + everyone/everything in/on your truck that wasn't on it when it rolled out the factory door, subtract all that from your payload. I'd suspect your 3/4 ton payload to be 2500-2800lb, possibly as much as 3000lb but doubtful.
Just FYI! Airbags are for leveling your truck when towing, they add ABSOLUTELY nothing to the "carrying" capacity of your truck + the the weight of that equipment also comes off of your available payload. Also attempting to tow a 17900lb 5th wheel rv that truck would need over 4000lbs of payload, which I'm guessing it's NO WHERE near that.
In the real rv world the tow rating of a truck & the dry/shipping weight of a rv are meaningless is calculating weights to match truck to a rv.
Not trying to rain on your parade, just stating rv weight facts for the safety of you & yours along with everyone else on the highway with you!
What you do, or not do, with this information is totally up to you! Be safe!

[jasin1]

Check this out ..looks like the wire was on the trailer

https://www.google.com/url?sa=t&rct=...2LQSgPlEqtcxVE

[Mark_TX]

Thank you all for your feedback on the payload capacity. Opened my eyes to alot of info I didn't know.

Now to figure out the brake issue.

[chuckster57]

Welcome to the forum

Let’s try a couple of quick tests, you will need a DC amp clamp.

Look for the break away switch. Identify with an Ohm meter or test light which is the COLD side (the wire with NO voltage on it). Place the amp clamp on that wire and pull the pin. Should read 12-16 Amps. Post results and we will continue on.

[Mark_TX]

Originally Posted by chuckster57

Welcome to the forum



Let’s try a couple of quick tests, you will need a DC amp clamp.



Look for the break away switch. Identify with an Ohm meter or test light which is the COLD side (the wire with NO voltage on it). Place the amp clamp on that wire and pull the pin. Should read 12-16 Amps. Post results and we will continue on.

I don't think I have a DC amp clamp. Will have to dig through the tool box.

[Mark_TX]

OK I just replaced my 12v charging fuse and hooked up to the horse trailer. Charging is working and the brake controller doesn't throw a fault when I apply brake controller power.

So it is the RV. I will dig into that connector next and make sure pin to pin matches truck.

[chuckster57]

Should be industry standard unless P.O. Did something different. I’ve only seen that 1 time in 20 years. Quick easy test assuming the trailer battery is charged.

Use this picture and make a short jumper.

http://www.countrytrailer.com/uploads/7wayplug.pdf

DO NOT jumper positive to ground.

Jumper power to TM (marker lights) check lights
Jumper power to LT (left turn) check light
Jumper power to RT. (Right turn) check light

Next is power to brakes, when you jumper just listen for the magnets to grab, and disconnect right away.

[ChuckS]

This should be useful... Pinout on 7 way RV connector and a pic of my pinbox electrical connections inside the junction box on the pinbox...

Your Montana is the same wiring convention..

Since you blew the 30 amp charging fuse on your truck when hooked to the Montana you got issues that need resolved on the RV BEFORE you plug back in

[Mark_TX]

Originally Posted by ChuckS

This should be useful... Pinout on 7 way RV connector and a pic of my pinbox electrical connections inside the junction box on the pinbox...



Your Montana is the same wiring convention..



Since you blew the 30 amp charging fuse on your truck when hooked to the Montana you got issues that need resolved on the RV BEFORE you plug back in

Attached is my truck plug diagram and if I am looking at the keystone diagram and my truck diagram everything matches.

Truck is now charging the RV battery so something else must have previously blown that fuse and I didn't know it.

Brakes are still throwing error.

I opened up the box at the RV hitch and everything looks factory crimped but I will map wire to wire and make sure everything matches up.

[Mark_TX]

I forgot to mention that the RV is the legacy package so it has disc brakes.

[travelin texans]

Originally Posted by Mark_TX

I forgot to mention that the RV is the legacy package so it has disc brakes.

With the disc your GM requires a converter of sorts to operate the disc brakes. Sorry I don't recall what they called it, but when I added disc to my 5er they had to add this item so the truck brake controller would recognize the disc.
Contact Performance Trailer Braking, they installed my disc, they should able to tell/sell you what you need, great customer service.

[Mark_TX]

Originally Posted by travelin texans

With the disc your GM requires a converter of sorts to operate the disc brakes. Sorry I don't recall what they called it, but when I added disc to my 5er they had to add this item so the truck brake controller would recognize the disc.

Contact Performance Trailer Braking, they installed my disc, they should able to tell/sell you what you need, great customer service.

Great thank you!!!!

[Javi]

Originally Posted by Mark_TX

Great thank you!!!!

Just a note.. I don't fool with the Chevy factory brake controller but with my '15 Ford I had to switch the controller to electric over hydraulic when the disc brakes were added. No additional adapter was needed.

Have you told the truck that the trailer is electric over hydraulic????