RV battery/converter question

[JSooter]

While troubleshooting to find out why my MaxBrake stopped working, I discovered that my RV battery is at 22V.
I disconnected the battery and it still sits at 22v.

The RV converter/regulator output (at battery connection measures 22V while loaded or unloaded). Inside the RV, I measured the DC from the cigaret adapter at 22V.
Based on this, it seems to me that my converter is bad.


Any thoughts?

 

[RVTRKN]

At 22 volts, it should have cooked the battery. Was the battery disconnected when you checked voltage of the battery? And if the voltage output is 22 VDC then you have a problem with the converter. Also, the lights should be brighter than normal, if it doesn't blow the filament first. Don't run your pump or furnace until you get it right. I have to ask it, but i'll assume you know how to use your meter, or you might have it on VAC, sorry had to ask!

 

[AH64ID]

That seems really odd, the battery should be scalding hot at 12V.. unless it has 2 12V that someone hooked up wrong.

A busted converter is possible, but I think other things would have gone whacky in the truck when hooked up.

Aside from overall voltage the battery on the trailer has nothing to do with the max brake unless the emergency brake is tripped with the max brake hooked up.. Even then the truck should have issues with 22V.

 

[JSooter]

Ok, got this one figured out...replaced 9v battery in multi-meter and back to normal!

I decided to check my meter on a known good battery. It also measured 22v. The multi-meter didn't display a low battery indication, but that solved the problem. Guess it's been awhile since I used the meter.

Lesson learned!

Thanks everyone.

 

[AH64ID]

Cheapest over voltage fix ever...

So, what's the max brake doing? Or not doing?

 

[JSooter]

So, what's the max brake doing? Or not doing?

The Max Brake was working great for several years. This season when I connected the trailer:
1. The Max Brake doesn't seem to wake up when trailer connected to truck
2. The message on the Max Brake reads "check trailer wiring"- same message that I usually get when no trailer connected.

My first suspicion is pin 2 (brake signal) of the 7 pin connector on trailer is not making a good connection and thus the Max Brake never senses a load. I'll start by cleaning all contacts on both ends of the 7 pin. That's what I was originally in the process of when I was sidetracked by the multi-meter issue above...

Any suggestions on how to test the Truck's brake output signal at the 7 pin connector?
I don't think a volt meter (pin 2 to ground) will tell me much without a real load attached. Maybe a troubleshooting idea is to jumper an old headlight between pin 2 and ground and look for varying brightness as brake pedal is depressed?

 

[RVTRKN]

Its voltage output will be less than 12VDC when pedal is lightly depressed verses full voltage at 12VDC when fully depressed. A light might help in the same manor if its a one man job.

 

[JSooter]

Looks like I have confirmed that the MaxBrake IS working.

When I measure pin 2 (brake signal) of the 7 pin connector to ground with a volt meter, it measures 12v and never changes, regardless of manually activating the controller.
However, if I connect a load (old head light) between pin 2 and ground, the light slightly illuminates and the voltage is something like 0.25v. As I manually activate the controller, the voltage increases and the light gets brighter- thus i believe that I can confirm the controller is working....now it looks like I get to tackle the trailer side of the equation.

 

[RVTRKN]

If you have another trailer you can connect up too, that would be a quick troubleshooting tool.

 

[CBari]

First thing to check is the ground side of the trailer brake wiring. Some manufactures run the ground wire all the way back to the plug others ground to frame, but if ground is bad or weak the brake controller won't sense a load.