Alternator not charging on 2003 CAT 3126

[judway]

I have a problem with the alternator on my CAT 3126 engine. It sometimes starts charging as soon as I start the engine and sometimes it may not start charging until after 30 minutes of travel, maybe even longer.
I discussed this at the forum SE Rally and others here in Florida.

It appears that 12Volts supplied through the ignition switch is needed to be applied to the alternator feld to get it started. The alternator is in such a location that it is a major effort for me to test and see if that is the problem.

I checked the Winnebago electrical drawings but found no information on the wiring. The wiring is probably shown on Freightliner drawings. In the past it has been a lot of problems getting access to their drawings.

Has anybody had the same problem and what was the solution? I have been able to keep the chassis batteries charged by other methods. TNX.

 

[Harry B]

I know that my coach does not use an excite wire and may be the same in your case.  However I am pretty sure you are not going to find this on the Winnebago wiring diagrams.  You are going to have to look on the Freight liner schematics.

 

[Mavarick]

First I would have a look at your belt and alternator pulley to make sure it is not slipping, etc. or there are other mechanical problems.
I?m not sure if your MH has a battery isolator or something similar that the alternator is connected to in order to charge both sets of batteries. If so, that connection would need to be checked to make sure 12v is getting to the back of the alternator, which is all it really needs. Assuming you have the original Leece Neville it has a built in regulator.
I also assume because you are using chargers that you are not just trusting the dash indicator and the alternator really is not charging, and, you have checked the batteries to make sure one is not bad. A really bad cell could pull voltage down enough to stop the alternator from seeing full battery voltage.
Usually when this happens it is either bad contacts in the regulator or brushes in the alternator. If all else checks good I would remove the alternator and bring it in to be rebuilt (to a starter/alternator shop) as my guess for a replacement could be over $500.
Sometimes you can get them to start charging by revving up the engine a bit to spin the alternator faster and then letting it go back to idle. Hope it?s something simple.

 

[Mark R.]

Many of the big alternators have  magnets that get week over time and some come week from the Chinese factory, I am only familiar with the Lease Neville magnet situation. On many of these alternators there is a sense wire that goes to your tachometer for RPM pulse. In my MH I attached a wire with 12VDC to a small momentary push button and from the switch to the tachometer post that has the wire that goes to the alternator. When I start the engine I push the button for a split second and the tach jumps up and the volt meters jump up. If your tach. does not work till you alternator starts outputting you have this set up, if your tach is alive before your voltage goes up you  have a different setup. Good luck.

 

[Gary RV_Wizard]

It's definitely in the chassis wiring rather than Winnie's.  Maybe a call to Freightliner Custom Chassis would get some help - their Customer Support line is usually excellent!  Call 1-800-FTL-HELP and have your VIN handy.

To get the chassis wiring diagrams requires a subscription to the FTL support web site, Access Freightliner - http://www.accessfreightliner.com/
You need to register yourself as a one-truck fleet to get an ID and password for the site. A nuisance, but it works.

 

[judway]

Thanks to all for the information and suggestions.

 

[Mavarick]

Don?t let the LN remote sense wiring fool you, it is not that difficult to work with. The only real difference is 4 wires on the back instead of 3. The typical 3 wire LN alt has a ground wire, a hot wire that ends up at the batteries (large wire) and a smaller wire that is hot when the ign switch is on. The ign switch wire is what excites the alt.
The only diff with a remote sense is another (4th) small wire going to an isolator etc to monitor voltage. This helps the regulator to adjust output to extra batteries etc. like used in marine and industrial also.
On the MH series I assumed they use the remote sense, 4 wire style because of the dual battery sets. With your ign key on just make sure you have two hot terminals on the rear top of the alternator. They are both smaller wires, around 12 or 14 ga. The other large ga wire will run to the batteries and the 4th will be a ground. If you have the 3 wire version it does not have the remote sense so 1 hot with the key, 1 ground and one large wire going to the batteries. Look at the back of the alt and count the wires going to it. Going from memory here so I can go look at mine if needed. I?ve never had to pay any attention to it except that it was a LN style (knocking on wood). I know they are a pain to get to which is why I suggested starting at the battery or isolator wiring and working back towards the alternator.
The only thing I remember on the tach hookup in the industrial side was certain style tachs were hooked to a terminal so they could sense the pulse from the alternator and this would drive the tach. This would also let you know the alt was working but these style tachs were handy on long runs (away from eng) as compared to the cable style. Hope this helps.

 

[Sparkyz]

Any chance of a photo of the back of the alternator?

 

[judway]

I am going to look at everything in about a week to see what the situation is. The alternator is difficult to get to. I have to remove all of the stuff under the bed and then the bed to get adequate access to the problem. I will probably start Dec 10 or 11. I believe I can keep everything under control by then. I won't need the MH again until Jan 10.

 

[judway]

I just got the bed removed to gain access to the engine. The alternator has a big wire which goes to the battery somehow, a larger red wire (probably #12)and a smaller red wire (probably #14).

The battery wire has 0.00 volts.
The larger red wire has 12.4 volts (battery voltage).
The smaller wire has 11.71 volts (control voltage)

The battery wire goes to the isolator.

It appears to me that the alternator is probably bad. It is a Leece - Neville 160 Amp unit.

However, it started both coming and going to our campout last weekend somewhere along the way.

I called Freightliner and the representative came to about the same conclusion.

He emailed me a complete set of wiring drawings for the chassis.

Any ideas!!

 

[judway]

I took the MH in to my local service shop and they removed the alternator and had it rebuilt. It was reinstalled and everything worked fine during the trip back to the house.

However, it made a big hole in my wallet.

 

[Kim (skyking4ar2) Bertram]

Would you be willing to share the size of the big hole?

 

[judway]

Rebuild the alternator was $340 (about 1/2 the price of a new alternator).
3 hours labor @ $80
Miscellaneous stuff and taxes $40.10

Total $620.10

I had all of the bed removed and made easy access (if that is possible) to the engine.

I now have to put the bed back in to complete the job.

 

[Kim (skyking4ar2) Bertram]

Thanks, Wayne.

I think that gives some perspective to everyone who has questions about "how much does it cost to maintain a diesel?"

Your prep work obviously was worthwhile. Labor always make my eyes water...  :'(

Thanks for the info!

Kim

p.s. I just traded out of my Cat 3126 - now I know what I missed!  ;D

 

[judway]

I have a little over 80,000 miles on the MH and have had very little costs due to failures. However, over the past year I had a radiator tank failure and a ride level controller failure that cost over $700, An engine shutdown and check engine light at about $1000 and the alternator at $620. This is over $2320. Over about a 7 year period is not very bad. The same problems could have happened to a gas engine and the gas engine mechanics cost about the same. The biggest difference seems to me to be having to change about 20 quarts of oil instead of about 6 quarts for the gasser. Some of the other maintenance items cost more for the diesel, such as air filters.