Alternator Charging Problems

[Tim Bentley]

My alternator does not seem to be charging the batteries.  When I start out in the morning the charge rate reads 13.9 and as I drive it drops off to 12.4 and below.  Have been running the generator to recharge when it gets low.  Yesterday I removed the top of what I think is the regulator and cleaned the contacts and replaced the brushes.  Don't do this unless you have read the how to as they are difficult to get back in.  
This has helped but only intermittently.  Now it charges off and on.  My next step is to replace the alternator as I have a spare.  Does anyone have any other suggestions as to what the problem might be?

[Tom Halter]

Tim I noticed the problem you are having with the alternator charging. If the generator will keep the chassis batteries charged then yes your alternator has an issue. You can have the old alternator rebuilt for alot less than a new one would cost. This normaly only takes a day or two at the most if you can find a reliable shop to do it for you.

[Bert Novak]

Hi Tim
Sometimes the crimps on the wires at the alternator are not the best; pull on them and see if they separate.
AutoZone will check the alternator for output for free if you bring it to the store.
If it puts out 14.4+ volts on the test rig its more than likely OK but might be intermittent.
Check the wires at the battery for corrosion and the crimps on the wires going to the BIRD controller.

If you have a spare alternator install that and see if the symptom changes.

I had an intermittent problem on the boat that had the same symptom and it turned out to be a intermittent open winding in the rotter following a lighting strike in Costa Rica.

If you want to talk it over give me a call at home or on the cell phone 951/244-4580, 951/415-0079
Bert

[Steve Rankin]

Your charging voltage should be between 13.8V and 14.3V.  

The most common problem is a defective regulator.  They are generally fairly easy to replace, depending on the access to the alternator.  

Diodes are another potential problem.  I prefer rebuilding my own Leece-Neville alternators as they are easy to rebuild and with a few tricks, a DIY rebuild is much more reliable than store-bought.  

[Tim Bentley Co-Admin]

Thank you all for the help.  Is the voltage regulator located on top of the alternator?  I.m not sure that the chassis batteries are charging on the generator or when I'm plugged in at night.  This morning they were at 13.3 when i checked.

[Charles Burden]

I have a few questions.  Tim are you talking about the "coach" batteries decreasing in charge as you travel down the road?  OR Are you talking about the "chassis" battery decreasing?  The reason I ask is that it sounds like you have to use the generator to charge the "coach" batteries because the alternator is not doing it.  If I am getting close please let me know because I had a similar problem.

Sometimes on coaches there is a battery isolation relay device (BIRD) that keeps the two sets of batteries separated purposefully.  This is so the use of the coach batteries do not discharge the chassis batteries while you are dry camping and leave you unable to start your engine or generator.  Conversely when you are in a campground your "shore" power is supposed to charge up your coach batteries and when they reach a preset charge level (13.4 or so) the relay allows the batteries to connect to each other so the chassis batteries can be maintained fully charged.  When traveling down the road the alternator is supposed to charge the coach batteries.  

If this is not occurring your BIRD or BIG BOY solenoid may not be operating properly.  

[Tim Bentley]

It seems to be the coach batteries that are not charging.  The problem is intermittent so if is difficult to tell.  I thought about the big boy, that may be the problem.  I.m home now so there is not hurry but I think I will replace the alternator and see if the solves the problem. If that doesn't work I'll look at the big boy

[Charles Burden]

Is this a new problem or has this been the case since you got the RV?

On our coach the circuit board that controls the BIRD and Big Boy has a plastic plug with the wires in the plug.  The technician found that the + and - leads were reversed.  Once changed the system charges the coach while riding and the chassis on shore power.  This wiring error was from the factory and had been this way for almost a year while at the dealer.    

[Tim Bentley Co-Admin]

This is a new problem. The coach has 90000 miles on it and is on its second alternator.

[Tim Bentley]

Had the alternator rebuilt, that costs $250 in San Diego.  I would have tried rebuilding it  myself but I could not even get the drive pulley off.  The rebuilt alternator in installed and it looks like the problem is solved.  The charge rate is 14.2 volts and seems to be holding steady but won't no for sure until my first trip,  

Thank you for all your help and suggestions.

[George Harwell]

Glad to hear your problem appears to be solved. I guess $250 isn't too bad considering the peace of mind it bought however I got mine overhauled by a local "good ol boy" here in Midwest city, Oklahoma for $79. I thought he had left out a 1 in front of the 7 but it was really a good job at a great price. By the way, I pull mine every 50,000 as a preventive measure. Have a great day!

[Richard And Babs Ames]

I feel if it is "ain't broke don't fix it" the alternator is a heavey duty unit and should work over several hundred thousand miles. We are over 100,000 with no problems with ours.  Main reason for electrical problems in our motorhomes is not using them enough on a regular basis. We are fortunate enough to be able to go several days every month of the year here in SW Central FL and the only problem we have had in over a year was it started to run a little warmer and it was corrected by a water hose wash out of the side radiator and tightning the water pump belt.

I learned to stay out from under the radiator when rinsing it out as the grime you get on you is very hard to get off. :-/