Dynamax Force HD Fuse Box Location

[houstonstroker]

I have a non working reverse wire in my 7 way plug. Can't seem to find any fuses that indicate trailer wiring. I found two under hood boxes and one in the inverter electronic bay. The two under the hood are marked the one in the bay is not. Anyway so where do the wires for the 7 way plug originate?

[pjcarnell]

So I went through the same thing today. The manual says behind the cab on the left side on the rail or cross member. Well I couldn't find it. Hopefully someone will chime in and solve it for both of us. Here's a picture of what those fuses down below are.

[halla]

Im not sure, wish I could help. But because there is a lot unlabeled, I switched every fuse in the coach, in the electric bay and under the hood to the smart fuses, they light up when they blow. So much easier to replace when you can find it

[IsataMatata]

Originally Posted by halla

Im not sure, wish I could help. But because there is a lot unlabeled, I switched every fuse in the coach, in the electric bay and under the hood to the smart fuses, they light up when they blow. So much easier to replace when you can find it

[emoji33][emoji849]🤯

[bclemens]

I have an email in to see what I can find out.

[bclemens]

Do you have back-up lights on the rear cap?

I am told the fusing is electronic and shuts off the tail light circuit(s) in the event of a short or overload. We have seen this primarily when someone hooks up a tow vehicle that is not LED. It overloads the circuits on the M2 which are set up for LED.

Once the short or overload is cleared, normally cycling the key will reactivate the circuit.

[houstonstroker]

Yes I have reverse lights in the back cap. They work fine. I added flashing LEDs to the rear to get peoples attention when I'm backing up. I tried to tap into the 7 way reverse wire and found that it was dead. So I tapped into the functioning rear cap reverse lights. I did some further checking today and followed the yellow wire from the center of the 7 way plug. It only went two feet and was terminated with a black rubber end. The Freightliner manual mentions a separate fuse box under the cab on the drivers side for trailer wiring. I found no such animal.

[bclemens]

They confirmed that for me today. The reverse wire does not get connected to anything. This was a legacy harness from 7+ years ago. No one seems to know "why" the reverse was never hooked up. A couple of guys here have trailers and they say none of theirs has reverse. Weird that this has not come up one time in the 3 years I have been here. All of our new harnesses for the multiplex units have this connected.

[houstonstroker]

Did they say anything about fuse location for the other wires in the 7 way?

[bclemens]

said those are electronically controlled.

[houstonstroker]

I'm trying to understand what "Electronically Controlled" means? Let's take the brown wire for example. I believe this wire is for your parking lights. Let's say it gets shorted to ground. Normally a fuse would blow. You correct the problem, put in a new fuse and you are good to go. What happens in the electronically controlled arena?

[bclemens]

The electronics shut off the wire and then you have to cycle the key once the short is corrected to fix it.

"electronically fused or current limited there should not be a need to use external fuses"

Consider it more like a circuit breaker, that automatically resets in the system.

[houstonstroker]

Well you learn something new everyday. Thanks for the explanation.

[pjcarnell]

Originally Posted by bclemens

They confirmed that for me today. The reverse wire does not get connected to anything. This was a legacy harness from 7+ years ago. No one seems to know "why" the reverse was never hooked up. A couple of guys here have trailers and they say none of theirs has reverse. Weird that this has not come up one time in the 3 years I have been here. All of our new harnesses for the multiplex units have this connected.

This could be an issue with trailer with surge brakes. The reverse light wire is connected to a solenoid that stops the trailer brakes from engaging.

[bclemens]

Originally Posted by pjcarnell

This could be an issue with trailer with surge brakes. The reverse light wire is connected to a solenoid that stops the trailer brakes from engaging.

Any decent shop that installs a brake controller and/or towing setup should/would test this and adjust accordingly. Which is likely why we have not heard about it before. Plus, i think most simple trailers like that use the 4 way, not the 7 way.