Unusual Electrical Problem

[kenk0001]

Hi everyone!

I have been following a lot of the posts on here and am amazed at the level of knowledge available!

So, with that said, here is what I believe to be an unusual problem. This problem MAY be something as simple as operator head space or, it will be technical in nature.

Vehicle: pristine 1989 Champion Eurocoach. John Deere Chasis with a ford 460 engine.

I drove the motorhome from Texas to our farm in Missouri. As I was driving, the charge indicator (voltmeter) began dropping. The lights began to dim. I was running the onboard, 7.6 Kohelor Generator in order to run the rooftop a/c units. The house batteries both were fully charged and the chassis battery was brand new. Belts were tight.

Eventually, the lights went out and I was forced to find a safe spot to park. Fortunately, we were within 30 miles from our house!!! The next day, I took a completely charged battery and changed it out, making the last leg of the journey to the farm.

I have exchanged the main battery for a brand new and drop tested it. It passes.

I pulled the alternator and had it tested; 14.3 on the output.

I had the voltage regulator tested; Passed.

I did a voltage drop test on the two house batteries; They passed.

I do notice a problem in the disconnect. The disconnect switch works fine on the main chassis. I can turn ALL power off and on there, and the voltmeter installed in the disconnect gives an accurate reading. However, the "house" switch, fails to disconnect/connect. The on light fails to light and the voltmeter reads nothing because its digital.

Can anyone point me in the right direction on this one? I worked at an RV place when I was a little younger and I have run my own garage, but this thing is stumping me.

I am including a picture of our newest motorhome, and even with this problem, I am still more than happy....okay, forget the picture, no matter what format I save the pic in, it says its too big. Diet time?

[wolfe10]

Couple if possible issues:

With generator running, both the 120 VAC converter, charger or inverter/charger should be charging at least the house battery and on many coaches the chassis battery as well.

With the engine running, the alternator should also charge both battery banks.

The alternator and converter both working together can lead to some strange voltage readings.

But, it sounds like you have a ground or battery connection issue. After checking connections, use a voltmeter and move from batteries toward the house to see where you are loosing power.

[kenk0001]

omg...NOW that was FAST! LOL...thank you very much! You are also correct about the charging process. I read in the owners manual how the onboard generator should be charging both battery banks, and the alternator SHOULD be charging the house batteries as well. When the brand new chassis battery was installed, the voltmeter would show about 14.3 output. As I ran the motorhome, that number would dwindle, slowly. At one point, I got underneath the engine area so I could test the alternator output directly off the back of the alternator. This was after an hour or so of running, and the best reading I could get was 7.8/8.1. When I pulled the main battery back out, put it on a trickle charger for a day or so, put it back in with a full charge, reading the volt meter at the very same output location on the back of the alternator would go back to a 14.3 reading. Then, just as before, it would slowly start dropping. This is what confused me. I thought the altnerator should have still been reading the same output....but then again, I thought my 5th grade english teacher gave me a wrong grade for a book report. lol lol...

[kenk0001]

ohhh..forgot to mention; The dwindling reading was the reason I pulled the alternator to have it tested. When it tested good, I didn't believe it. I took it to another shop and had it retested again. Again, same results.

[wolfe10]

Well, if the alternator only quits charging when hot, a quick test at an alternator shop may not show it bad. I can think of only a few things that can cause those symptoms:

Bad alternator

Bad regulator (may be build into the alternator or may be separate)

Bad connections, particularly if remote sense alternator.

Verify that the alternator belt is properly tensioned.

[dickandlois]

The information you have supplied leads me to think that you have a defective regulator in the Alternator.

The fact that the voltage charging level drops over time even with a fully charged battery, points to a regular diode failure.

The current output is dropping. This would account for the 7 volt drop in output as things heat up.

I have to believe that the shops that tested the alternator did not run a load test on it. Just a voltage reading when it was cool.

Brett, is correct in regards to the connections needing to be clean and tight on all the batteries and at the alternator.

Also check the grounding cables between the engine and frame.

Rich.

[kenk0001]

Thanks so much for the confirmation! I did check the grounds and they were good. The battery connections were all clean and tight. The thing that threw me was the two different voltage readings. I know they did not do a load test, rather they just checked to see what the output was, and as both of you pointed out, the alternator was cold during both tests. Easy to see where the test could have been wrong. It has an internal regulator and I believe the easiest thing for me to do now is to simply replace the alternator and then see what happens.

I will keep you informed and follow this forum more closely!

Thanks again!

[dshagen]

I have a friend that had a Bounder on a John Deere chassis with a big block Ford engine, He had a charging problem that turn out to be the electric choke on the carb. I don't remember what year it was, but the alt wiring on this one feed the choke element.

[chucknewman]

Dshagen posted "...so, put it back in with a full charge, reading the volt meter at the very same output location on the back of the alternator would go back to a 14.3 reading. Then, just as before, it would slowly start dropping. This is what confused me. I thought the altnerator should have still been reading the same output...."

Keep in mind the alternator output is connected directly to engine battery + post. If the alternator is not charging the battery, the slowly reducing battery voltage will be seen at the alternator output post as well as the battery post.

I've had this same issue before. The alternator brushes lose normal contact with the commutator when it warms up. In my case it was due to worn down brushes, but it can also be caused by weak brush holder springs. I would take the time to inspect the brushes condition and alignment on the holders. Much cheaper to replace than entire alternator, depending on brand and design.

Note that when a diode or other solid state component fails, they usually don't recover. Once the junction opens or shorts, they stay that way.

I don't see any connection with your problem and the electric automatic choke. If the electric element in the choke shorted to ground it should be protected by a fuse or a fusable link.

[kenk0001]

OKAY...change number 200112; Today was another new symptom. BEFORE I ever started the engine, before I did anything, I had the thought that the generator SHOULD charge the chassis battery. I did not know if the battery was low. It was just a thought. So, I went and opened the generator storage box and was going to manually start the generator. NOTHING. I thought well, maybe the disconnect has to be on (the chassis side because the disconnect still doesnt show anything from the house side) So I go and throw the disconnect to power use. I go to the drivers seat thinking I would remotely start the generator. Still nothing. Now when I had quit pulling my hair out earlier, I KNOW the batteries were charged. The disconnect was in the storage position (chassis side only). So, I decided to start the engine and see what the "in dash" voltmeter would show. The engine cranked a little slowly, but started. The charge hand immediately went from showing about an 8.? to 13.8, and it began to charge the chassis battery. I went and grabbed a battery tester w/volt indicator and put it on the house batteries. They were more than half way down but starting to slowly recharge.

Okay, so here we are; The battery connections are all tight and cleaned thoroughly. The alternator tested good. The regulator tested good. The house batteries are 1 year old/filled with water and takeing a charge. BUT...they drained down, and I believe they were in the process of draining my chassis battery. Anyone have any ideas?

[wolfe10]

No, not all coaches are wired for the converter, charger or inverter/charger to charge the chassis batteries. And, of course the same thing would apply to both shore power and generator power-- they are just different sources of 120 VAC for the converter, charger or inverter/charger.

And, you have confirmed that the alternator is charging both battery banks.

Assume that your generator DID charge the house battery bank.

Brett

[kenk0001]

Now I am confused. The alternator was the only thing running. The generator was not running and the voltmeter indicated that the house batteries were coming up in charge.

[RVerOnTheMove]

That's good. That means the coach is wired so it will charge all batteries from multiple sources. You will need to ensure that there is a battery isolator in the circuit or the house batteries will also drain your starting batteries and strand you somewhere.

[wolfe10]

Now I am confused. The alternator was the only thing running. The generator was not running and the voltmeter indicated that the house batteries were coming up in charge.

As I said: "And, you have confirmed that the alternator is charging both battery banks."

[kenk0001]

lol..sorry for the ambiguity there!

So, if the alternator is charging both banks, then the alternator cant be the problem right? Is it possible that running both overhead ac units off of the generator (50 amp output), while the motorcoach was running, could have possible drained the chassis battery?

Any particular clue as to where I would look for this elusive beast?...for that matter, what it might look like?

This is making me feel like quite the idiot. lol...and I really am mechanically inclined!

[RVerOnTheMove]

lol..sorry for the ambiguity there! So, if the alternator is charging both banks, then the alternator cant be the problem right? Is it possible that running both overhead ac units off of the generator (50 amp output), while the motorcoach was running, could have possible drained the chassis battery?

No, but you do want to verify that you are charging while using the generator (no engine running) and then you want to ensure that with both running you don't have an issue.

[dickandlois]

The key to the problem is still heat in my mind.

You mentioned that the engine started slow, indicating a low charge state of the batteries.

Everything was cold and the alternator started charging the chassis and coach batteries. This should happen in all the different model coaches if all fuses / circuit barkers, connections are clean and tight.

When things start to heat up (Engine and Alternator) the regulator diodes can go into an avalanche state and fail to function properly. This lowers the charge current and that relates to a low voltage output.

Did you look at the information I posted at this location?

http://community.fmc...nator-problems/

First picture shows one of the style regulators used and this problem reoccurred (s) on my unit due to heat.

Rich.

[kenk0001]

Yes I did! The pictures are worth a thousand words! I appreciate the time you took to do that for us less than educated mechanics!

[kenk0001]

Okay....I spent about four hours checking wires yesterday. checked cables again. Cleaned and recleaned. Checked the batteries again. THIS time, something new. After having them (house batteries that are approximately a year old, good water levels) on a 2 amp trickle charger (I had two trickle chargers going and disconnected the batteries from each other entirely) After charging all night and a portion of the morning, One wouldnt pass the load test. One passed, one failed. I guess (stateing that rather quizzically) that the battery that failed the load test must have been drawing current out of the chassis battery and causeing the lights to dim.... I say that, but I really dont have a clue.

[dickandlois]

Just One bad cell in the set of batteries can cause the discharge problem !!

The alternator can recharge them only to a point and in doing so, can over time damage the alternator in a number of ways. The extra load just works them to death.

Fleetwood came out with a change years ago, changing the OEM 130 amp unit to a 160 amp. unit for that very reason. Load and Heat.

We keep adding more of a load to them over the years, so the alternators,inverter / chargers and battery banks have been sized larger. No Free Lunch.

You now have a better understanding of the system and have moved up the learning curve all of us are still on. Manufactures are always changing and adding items to make the coaches safer, user friendly ( although more confusing when things act up) and they do not add some information to there user manuals that would be very nice to have, if not for all owners it would be helpful for service center technicians for a reference.

Rich.

[wolfe10]

Ken,

It is unlikely that a bad cell in a house battery would discharge the chassis batteries, as the two battery banks are separated on most coaches.

With your low battery, best advice is to fully charge ALL batteries (separately is best) and then load test them. If these are wet cell batteries, another easy/inexpensive option is to buy a battery hydrometer at any auto parts house (under $10) and after and only after fully charging them check their Specific Gravity.

A bad cell will give all kinds of electrical problems, so eliminate that as a cause first. It this the likely cause of all your electrical issues? Probably not, but replacing a bad battery is a good place to start.

Brett

[kenk0001]

Do you know if there is any problem with changing out a 100 amp alternator with a 160?

[kenk0001]

Thanks Brett! That was the one of the questions I was trying to figure out; Chassis battery and house batteries can be recharged off the alternator. Chassis battery and house battery can be recharged off the generator. BUT...that doesn't necessarily mean that chassis battery can be drained by house battery.

That's the question of the hour in my mind now.

[dickandlois]

The two sets SHOULD be separate. Only tied together when the Aux Start switch is engaged.

The contacts of the aux relay could be welded to gather do to a high current draw in the past. NOT a common event thought. An auxiliary relay with constant current through the coil should be running very hot, should the switch contacts for the aux start switch be connected all the time by some kind of internal failure. Again this would be an odd failure.

Brett mentioned reading the Hydrometer levels in all the cells to see if you have a bad cell in one battery.

Changing the Alternator to one rated at 160 amps is common and many coach owners are going to 200 amp units.

Rich.

[hermanmullins]

Brett spoke of using a Hydrometer to check each cell of a Battery. I had both of my chassis 12 volt Batteries test poor on my load tester. I took them both to Interstate to have them checked and replaced if necessary. One of the first things the tech did was get a tool and pop off the plates covering the cells he said that the acid was low. My comment to him was" When the Top of the Battery has a sign saying Maintenance Free and there are no removable caps for you to remove I took that to mean Maintenance Free"?

They exchanged both Batteries at no charge. He and I still get along well. .

Years ago there was a test you could do on your Battery. It was called the SUN 3 Minute Test (Sun Electric Automotive Test Equipment). What your did was to clean both + & - post. top off the fluid, put on the charger and connect a volt meter. Then turn on the charger to the max (45 amps at that time) for 3 minutes. Most Batteries would ready 10 to 12 Volts but begin to climb to 13.5 volts. However if the volt meter continued to climb on up to 16+ volts during the 3 minutes you has a Sulfated Battery. A Sulfated Battery means that over the life of a Battery the fluid got low enough to uncover the plates. Each time this happened flakes would fall off and build up under the plates until they shorted out the cell.. Each time you would charge the Battery it would work fine for most of the day but the next morning the Battery would be dead.

Now after all that could kenk0001 have sulfated Batteries??

(I hope I spelled Sulfated correctly)