Jump to content

Alternator not charging.


Recommended Posts

I have a 2002 40' Allegro Bus on a Freightliner chassis. Chassis serial # 4UZAAHBS72CJ81240 if that helps. 8.3 Cummins diesel.

It worked when I quit using it last winter. I changed the location of the start batteries but didn't start it.

Of course you should always look at the last thing you did when a problem arises and I did. I can't see anything amiss in the connections to the battery.

In trouble shooting I notice the output cable on the alternator does not have voltage. Everyone I have seen that wire was hot. Off or running there is no voltage.

I suspect this is the problem but I need to verify that cable should be hot all the time.

It would also help if someone knows where it goes. Direct to the battery or to a solenoid?

Any help would be appreciated.



Link to comment
Share on other sites

Sorry, not being familiar with your alternator or your coach wiring, I cant help. Also I dont know if the alternator has an internal or external voltage regulator. However, like you, the smaller truck/car/RV alternators I've seen and used would indeed have hot battery voltage present on their main output stud terminals. If they do not perhaps their is a normally open relay device in the circuit somewhere between the alternators output and your battery WELL DUH. That could explain no voltage when NOT RUNNING, however if there's still no voltage on the main output stud/terminal WHEN RUNNING hmmmmmmmmmmmmmmmmm the alternator my be bad orrrrrrrrrrrrrrrr its not being excited as many require initial external excitation prior to self running. Also if there is some sort of a normally open relay between the alternator and battery, I would guess it activates and closes ONLY if it senses alternator output power, IE no alternator power, no relay closing, so not voltage.


I guess there's a good ground connection from your battery bank ground to the alternator????


A wiring diagram is what we need and I have none


John T

Link to comment
Share on other sites

One of the things I was doing when I moved the start battery is remove and clean all cables.

I am quite sure the ground is good.

Yes I wish I had a wiring diagram.

Following that cable is going to be difficult (and dirty) but if I can't find a diagram or someone who knows that may be the only way.

Link to comment
Share on other sites

Update. I put a mirror behind the alternator so I could see just what was there. There are 2 heavy red cables. The one I didn't see had a boot over it and it is hot. Looks a little corroded so tomorrow I will remove it and clean it. Looks like I will need an alternator rebuild.

I did sign up for Access Freightliner and just got accepted.

I have yet to figure out how to get any information from the site.

Link to comment
Share on other sites

Doug if its not too hard to remove the alternator. Take it to an auto parts store...lots of them have a machine for testing alternators and starters and such. This machine will tell you what is wrong.

I agree have them bench test it. Did you label everything when you disconnected it? Some times not a bad idea if your doing major changes.

Link to comment
Share on other sites

I have not disconnected it yet. And yes I will label everything for sure.

Thinking about it, it can't be corrosion because I put my lead on the post and it was hot.

I have located a rebuilder in Sault Ste Marie, Canada that I hope can rebuild it. As we live close it is a short drive. Good idea about having an auto store check it.

I have another problem I want to address before I disable the engine. I have a hydraulic leak on the transmission cooling hose going to the radiator. I want to fix that before I disable the engine. There is a bunch of hoses in the area and every one of them dripping with tranny oil thrown by the rad. fan. What a mess.

I have it pressure washed and hope to find the bad hose today. At least I hope its a hose and not the radiator. This motorhome has been pretty trouble free but you know the saying about trouble in 3's. Well this trip the steps also failed in the down position. It needs a new motor. Minor but not when you cannot retract the steps. I disconnected the drive, drilled a hole in the side of the step, attached a heavy electrical wire and tied it off to the entrance handle.

Redneck repair but at least I didn't wipe them out and I could still use them.

Running out of time before we leave with out boat so I have to get going.

Link to comment
Share on other sites

I feel for ya Doug. Older MHs will occasionally give us trouble but I like to console myself with the fact that I bought a high quality MH with most of its life still ahead for a pittance of its new price and its worth some time and money keeping it in good condition. The alternative is a newer unit but even there the problems can still crop up.

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

RVers Online University


Our program provides accurate individual wheel weights for your RV, toad, and tow vehicle, and will help you trim the pounds if you need to.

Dish For My RV.

RV Cable Grip

RV Cable Grip

All the water you need...No matter where you go

Rv Share

RV Air.

Find out more or sign up for Escapees RV'ers Bootcamp.

Advertise your product or service here.

The Rvers- Now Streaming

RVTravel.com Logo

  • Create New...