Time for a new Alternator?

[tiredvet]

I left the shore power off for a few weeks and when I went to start it I could hear the lift pump come on and had no dash lights, I tried to start the rig and only herd a little clicking from the solenoid.I was showing 11.9 volts on the start batts.I put a trickle charger on them and the next day they were at 12.3.It seemed to crank a little longer than normal but did start. while running It showed only 12.0 volts.Battery cables are clean and tight.I put the charger back on and the following day the start batts were at 12.5. I went to start the rig and it fired right up but the dash lights will only come on after the coach is running,after 4 more starts It would do the same thing (no dash lights) until the rig is running.The highest volt reading that Ive been able to get while it's running is 12.1.I also have a blinking green light on the echo charger. When I shut the rig off I'm seeing 12.3 volts on the start batts.On the house batts they have always stayed at 13.6-13.8. Not knowing all the history on our coach and owning it now for 3 years I'm thinking of replacing the start batts and the alternator. I may be missing some things so let me know where. When checking the volts I took readings from the battery isolator and relay as well as the batteries.

[Alpine Dave]

Sounds to me like your starting battery is good but alternator, isolator, or cable connections may be the problem. Check the voltages at all connection points in the bat/alt/isolator circuit to make sure there is no voltage drop across any connections. Also make sure the sense lead on the alternator has the same voltage as the battery terminal.

[YC1]

Make sure your fan belt is tight. If it is then remove the alternator and have a parts house test it for you. While you have the batteries disconnected charge them until they reach 12.7 volts. If they don't get there have them tested and replaced if necessary.

If you run the generator or plug into shoreline what are your voltage readings then? May as well make sure all of your systems are working properly.

[Dr4Film]

Your coach alternator should be showing about 14.3 - 14.4 VDC when the engine is running. You should also see about 14 VDC or more at your Chassis battery terminals.

If the readings are low then have your alternator completely rebuilt at a reputable rebuild shop. It should be less than $200 to install all new parts. Make sure you ask for original parts and not ones from China.

A trickle charger should only be used on a fully charged battery to keep it from discharging. Use a normal battery charger or use the charger that is in your coach to charge up the batteries if they are low.

Dr4Film ----- Richard

[tiredvet]

I agree Richard.My tender plus trickle charger will take more time than a battery charger would but thats all I have. Was able to get the dash lights to function correctly.I just unplugged the connector from the back of the ignition switch and put it back on. This morning the start batteries show 12.8 but not sure how they will do under a load. Is there a test I can do to tell if the battery isolator is good? I found a good price for a new Leece-Newville A0012824LC DUVAC alternator. Is that a simple swap in ? That is what is in the coach. I noticed I no longer have a green flashing light on the echo charger.There is no light at all on,the fuse is good so I need to take the tester tomorrow and hopefully solve that issue. Thank you all for your comments.

[StevieG]

Originally Posted by Dr4Film

Your coach alternator should be showing about 14.3 - 14.4 VDC when the engine is running. You should also see about 14 VDC or more at your Chassis battery terminals.

I just went through this and totally agree with Richard up to this point. I got all the same advise about the belt, grounds, and cable connections. If you can get a multimeter to the back of the alternator and it's not reading at least 14v coming out the back, it's toast...

If the readings are low then have your alternator completely rebuilt at a reputable rebuild shop. It should be less than $200 to install all new parts. Make sure you ask for original parts and not ones from China.

This is where I disagree with Richard... I would NOT have my old one rebuilt, but that's just me. For about $100 more you can get a brand new OEM alternator... Do it right once and forget it.

Dr4Film ----- Richard

[Mr_D]

Originally Posted by Dr4Film

Your coach alternator should be showing about 14.3 - 14.4 VDC when the engine is running. You should also see about 14 VDC or more at your Chassis battery terminals.

If the readings are low then have your alternator completely rebuilt at a reputable rebuild shop. It should be less than $200 to install all new parts. Make sure you ask for original parts and not ones from China.

A trickle charger should only be used on a fully charged battery to keep it from discharging. Use a normal battery charger or use the charger that is in your coach to charge up the batteries if they are low.

Dr4Film ----- Richard

Yep, our altenator was showing a low voltage output, both on the dash gauge and the VMSpc. Didn't pay much attention to it as everything worked OK for our short trips. Last year I pulle the alternator and got a new one, cost was just short of $500 w/tax to get the right one. Last month I took the old alternator in and had it rebuilt. Cost was $196 out the door. New bearing and both brushes. Keeping the old one for a spare although I'll probably never need it now.

[dennis45]

Just replaced mine at 70K with a brand new OEM Leece Neville for $429 and tossed the old one in the scrap bin. I likely won't have a drivers licence when it craters again.
Do it once the right way.

[Alpine Dave]

It if fairly easy to replace the OEM Leece Neville alternator with the same model. If you want to replace it with a more popular alternator, such as the Delco 28SI, here is a thread with some useful information: http://www.irv2.com/forums/f104/how-...si-195836.html

[Alpine Dave]

Before replacing your alternator, make sure the "key switch" DUVAC function is working. When you turn on the ignition you should get battery voltage on the "key switch" terminal of the alternator. This voltage is needed to enable the DUVAC function which excites the field winding on the alternator to get it started. If not, the alternator will not start and will act just like a dead alternator. This function is only needed when you have a diode based isolator. The isolator blocks battery voltage to the output of the alternator, which is used to start the field current in a normal single battery vehicle.

[Alpine Dave]

The diode isolator is simply back to back diodes with the center point going to the alternator and the end points going to the chassis and house batteries. The diodes prevent current from flowing from one battery to the other and current from flowing from either battery back to the alternator. With the alternator not running (or faulty) you should see 0 volts on the alternator output. With the alternator running you should see around 15 volts on the alternator output, about 0.7 volts across each diode, and about 14.3 (15-0.7) volts on the battery terminals. If you see much more than 0.7 volts across either of the diodes, the isolator is probably bad.

[tiredvet]

Solved the issue. Turned out to be a bad ground fuse. So now I have a spare alternator and that can be a good thing. Thanks to all for your input.

[YC1]

Where was that ground fuse located? What was it a ground for?

[Alpine Dave]

What in the world is a "ground fuse"? Please explain