03 is not charging my trailer

[grmayer]

The problem that I am having is that my 03 d/max is not charging my trailer. I have searched this web site. And it is still no luck


Please keep in mind that the brakes and all the lights work just fine. And a friend of mine has a 02 Chevy with the same trailer i have.

Hear is what I have tried
My truck and my trailer

[FisHn2DMax]

I think I can help? I went through the same thing a few months back. So bear with me, I'm going from my old memory... Stud 2 should be a 30 amp (max) fuse for the trailer brake controller( see back side of fuse under hood compartment lid.) Stud #1 Or B+ should have a 30 or 40 amp fuse installed to supply power to your trailer batteries.

My 03 had a red blank fuse called B+ in this location.

Good Luck!

:D

[MaxDiesel]

It's the B+ under the hood. Take out the Red plug and put a 40 amp fuse in it. That should bring power to the harness.

[BobW]

There was a post about a change in the plug wiring for the '03's here

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=5&t=000539&p=

[grmayer]

When I bought the harness from the dealer it came with a 40 amp fuse and I in stalled it into the stud #1*. Stud #2* already has a 30 amp fuse in it.


And where is the b+ fuse I don

[DonG]

grmayer,
Your two post are confusing. In the first post you say the 40 amp fuse is in stud #2. In your second post you say it is in stud #1.

Your second post is correct. The 30 amp should be in stud #2. This fuse supply power to the brake controller. The 40 amp fuse should be in stub #1, on the left. This supplies power to the trailer batteries. The B+ FisHn2DMax was referring to is a plastic plug that was setting in stud #1 position. You have to remove it to install the 40 amp fuse.

It sounds like your truck is fused correctly but something is amiss. Maybe the 40 amp fuse has blown. You need a meter to check it, and your trailer plug for power. The fact that another truck powers your trailer implies the problem is in your truck. If the fuse is good, then you have a wiring problem, maybe at the trailer plug itself.

If you are sure you have 12v at the correct pin on your plug at the trailer, I am at a loss. The pin you describe must not be the right pin. (By the way, the brake controller harness has nothing to do with supplying power to your trailer batteries. Don't worry about the harness, its working fine). The problem lies from the 40 amp fuse to the trailer plug and on into the trailer.

Good Luck, Don

[ 03-08-2003: Message edited by: Don G ]</p>

[grmayer]

Thanks Don

[FisHn2DMax]

Like Don G stated, if you have a 40 amp fuse at Stud#1/B+ then you should be getting +12V to the rear trailer plug at all times.

One question that I should have asked? Was your rear bumper trailer Plug factory wired? Or did you have it installed aftermarket? I know you posted that you had it tested, but trailer/hitch shops rarely test for the 12 volts for the trailer battery on the 7 pin connectors. If it was not factory wired, and the the 40 amp fuse is good and in location Stud#1, I would verify proper wiring at the rear bumper plug.


Good Luck!

;)

[DonG]

grmayer,
O.K. If the fuse is good then the wiring is bad.
I tried to find a circular layout of a trailer plug but could not. My seven pin trailer wiring reads as below:

1. white = ground
2. red = stop & left turn
3. black = battery charge
4. yellow = auxillary (not typically used)
5. green = running lights
6. brown = stop & right turn signal
7. blue = electric trailer brakes

Unfortunately, I cannot tell you the position of these wires, but the colors should match on both the trucks wires and the trailer wires.

Use a meter and go around the whole plug turning on various souces of power and verify it matches. If you get 12 volts when you should get 12 volts, then I am at a loss.

Good Luck, Don

[grmayer]

FisHn2DMax @ Don G


The truck came to me with the factory wiring all the way to the rear bumper.

All I add was the plug under the dash that goes to the brake controller. And the 40 amp fuse that came with that wiring harness.

Don G you are correct with your colors. Also the information that I got from the trailer shop is

If you are looking at the plug on the truck

1. White = ground (7 O

[DonG]

I came across a display of a seven pin truck plug, but it does not appear to be like you describe.

My seven pin is: going counter-clockwise

1. white = ground @ noon
2. black = battery charge @ 10:00
3. yellow = @ 8:00
4. red = @ 6:00
5. green = @ 4:00
6. brown = @ 2:00
7. Blue = trailer brakes. located directly in the center of the plug.

You do not list a center pin. If you do not have a center pin, then your truck is wired differently than a typical RV. You might have a utility type trailer plug.

Since your friend's truck works with his identical trailer, then I would map his pins and function, using a meter so you know exactly what turns on for each switch you activate.

Then use that map to set up your truck plug. If you get the same voltage he gets in the same position by using the same switch, then your truck has to work when you are done.

My truck also came with the rear plug wired but it does not look like you described. Your plug may be a dealer installed plug for a utility trailer.

Anyway, map your friends truck plug and then match it.

Good Luck, Don

[White Truck]

There are differences in manufacturers as to the wire colors, so the trailer may have different colors than what has been mentioned. What your truck has is the following:
(This is looking at the receptacle on the truck from the back as if you were plugging a trailer connector into it.)
1 o'clock is B+ (charges aux bat) and is red
3 o'clock is RH turn and stop and is green
5 0'clock is trailer brake and is blue
7 o'clock is Ground and is white
9 o'clock is LH turn and stop and is yellow
11 o'clock is running lights and is brown
Center post is trailer backup lights and is light green

Remember, these are the truck wire colors only, trailers often used different colors for these functions. What is important is that the function of the wires match, the color is NOT inportant and should not be matched unless you know they are the same. The flat 4 connectors used for small trailers ususally have matching colors, but any larger trailer that I have owned have usually not matched.

Another point to mention, 12 volts at the connector doesn't necessarily mean you have what it takes. Voltage is only potential, amperage is current flow. Voltage is accurate only when measuring a complete circuit, that is a working one. Open circuit voltage can be misleading.

DKB

[grmayer]

Just an update my friend brought over this truck to do some testing. And for some reason it is working just fine.

What we had the truck running. And it worked

And I tried that before I did my first post. Maybe moving and testing and cleaning the contacts helped.
it is working just fine

Thanks for all the help!!!!!!
smile.gif smile.gif smile.gif smile.gif

[DonG]

grmayer,

Glad to hear you got it working. You may have a wiring short or loose contact at the plug.

Something to keep in mind in the future.

Don

[FirstDiesel]

When I first got my DMax I still had to deal with my small trailer that had a 6 pin round connection. I bought an adaptor and when I hooked up my brakes didn't work. The brake tester module indicated that the wiring was correct and the test lamp even lit. I worked on the trailer plug and still no good. Finally a little "adjusting" of the pins in the trucks connector solved the problem.

You might have the same thing. Tweek the pins in the connector a little for better contact with the trailer plug.

[jjinatx]

I have the problem with my '03 3500 DMax not charging the camper batts. After searching the owner's manual, I still didn't have the answer so I tried here and think I found the answer. My fuse box has the B+ red plug in stud #1.

The owner's manual is very confusing because in the table on page 5-117, for Stud #1, it says "Auxiliary Power (Single Battery and Diesels Only)/Dual Battery (TP2) Do not install fuse". This is a direct quote. OK, so I have a diesel with dual batteries - so what the heck does this mean for me????? Reading this, it sorta sounds like you ain't supposed to put a fuse in stud #1.

My first inclination was to put a fuse in stud #1, since that was where the trailer 12V was on my '99 2500 gasser, but I was scared off by the owner's manual.

-jj

[Viking]

jjinatx, your book is correct. Diesels have two batteries in parallel. The second battery is NOT an auxiliary battery. You must use the fuse to get power to your trailer battery.

[jjinatx]

Viking,

Not sure you can say the manual is "correct" because the way it is worded is somewhat misleading and pretty much jibberish. They could have made it a little clearer.

I would have eventually removed the dummy plug and stuck in a fuse, but the warning about not putting a fuse in stud #1 if you have dual batteries kind a threw me.

Interesting that you point out that there is a "dual battery" configuration in some trucks that is not 2 batts in parallel. What is the configuration and what is it for?

Also, is the 2nd battery in the DMax isolated via a key activated relay, or are the batts always connected together? Sure wish I had a wiring diagram.

Thanks.

-jj

[DonG]

jjinatx,

Viking's answer is right on. On the diesel equipped trucks the two batteries always act like one. No chance of separation.

If you had a gas engine, you have the option of an auxilliary battery that acts separate from the main battery.

Install the 40 amp fuse in the left slot to charge your trailer batteries.

A word of caution : Once this fuse is installed, both your truck batteries are linked to your trailer batteries. If you draw down your trailer batteries without unplugging the trailer connection, you will also draw down both truck batteries. An isolation solenoid would be the best method of isolation.

Don

[jjinatx]

Don, Viking,

Thanks for the info. Yup, I know about the potential of the camper draining the truck battery. I installed a Hellroaring isolator in the camper when I bought it a few years back, so I don't have to remember to disconnect when camped.

-jj