Can I replace my alternator?

Topic: Can I replace my alternator? (Read 1788 times) previous topic - next topic

Can I replace my alternator?

July 24, 2014, 01:16:29 pm

TN RV recently replaced the fuel lines to both the generator and to the engine. They informed me that the alternator looks sooty and may need replacing. I have not experienced voltage fluctuations or charging problems. My intent is to have the alternator rebuilt or replaced. It is a Leece-Neville A0012824LC . I am aware of the four connections needed for this type of alternator. My neighbor, who does his own work on his class 8 Peterbuilt, says removing my Foretravel's alternator looks easy. I searched the forum and found a comment saying that the compressor belt needs to be removed before the alternator's belt is loosened (for a 96 U270). Looking at my 2000 8.3 Cummins, to my non mechanical eyes, it seems like loosening the one serpentine belt enough to get it off the pulley, is all that is required. To prevents shorts, he also recommends disconnecting the chassis and house batteries. (My wiring diagram shows the alternator output going to the center post of the isolator. So, no part of the alternator appears to be hot).
What are the steps required to remove my alternator? And the harder to answer question is can I do it myself.
Thanks
Bob
2000 U270

Re: Can I replace my alternator?

Reply #1 – July 24, 2014, 01:41:27 pm

The alternator is one of the easiest items to replace on these rear engine coaches (unless you have a rear radiator, which you don't). Just need a couple of wrenches to remove wires on back and mounting bolts. You would not need to remove the AC compressor belt unless you want to install a fresh belt along with the new/rebuilt alternator. Like you said, just take the tension off the serpentine belt and slip it off the tensioner pulley. However, I recommend you DO install a fresh belt, unless yours is brand new. Keep the current belt for a spare. As for disconnecting the batteries, this is always the safest procedure, and always recommended whenever you work on electrical equipment. You may have a sense wire going from the alternator to the "start battery" post on the isolator - this wire is HOT all the time. Why not take the opportunity, while you have the battery cables off, to clean up the terminals? Then you would have a new alternator, new belt, and clean terminals...after this job you would be good to go for many trouble-free miles!

Re: Can I replace my alternator?

Reply #2 – July 24, 2014, 01:44:39 pm

Hmmm.

I am of the "if it ain't broke don't fix it school. Â Since you can run without the alternator (start the generator, and use boost to combine chassis and house batteries) in an emergency - why not just wait until a failure, and then fix when convenient?

I have a 2000 as well, suspect mine looks "sooty" too

Interested in what you end up doing - take cell phone pictures and mark the wires when you take it off though

good luck!

Re: Can I replace my alternator?

Reply #3 – July 24, 2014, 02:19:34 pm

I would leave well enough alone, SOOT does no damage to a alternator, Atlernator should last forever unless batteries are abused and it runs hot.
Gary B

Re: Can I replace my alternator?

Reply #4 – July 24, 2014, 03:03:29 pm

If you have 100,000 miles on your rig, you could pull at your convenience and take it to a local electrical shop and have the bearings and brushes replaced. Should be under $100 and not a bad idea rather than having it go out on a trip. EZ to pull yourself. You don't have to worry about belt tension when you reinstall but I would spin the tensioner by hand to check for a dry or rough bearing. Cheap and easy to replace. Good time to replace the belt also. Get belt part numbers and buy stuff for about half online. Be sure to label wires and take a digital photo for reinstallation. Disconnect batts as there is probably a hot wire at the alternator.

When I was in the MB business in Germany, the dealerships had a program for the customers that didn't want to take a chance on a road failure. Once they were signed up, MB would replace starter, alternator, master cylinder, etc. at a certain number of miles before a failure might be expected. Good piece of mind but also good to have no credit limit on your CC.

Pierce

Re: Can I replace my alternator?

Reply #5 – July 24, 2014, 03:55:36 pm

Quote from: Tim Fiedler – July 24, 2014, 01:44:39 pm

I am of the "if it ain't broke don't fix it school. Â Since you can run without the alternator (start the generator, and use boost to combine chassis and house batteries) in an emergency - why not just wait until a failure, and then fix when convenient?

Me too. I had the alternator go out in Ohio, and drove the coach back to Kearney, NE before taking it off. Just turn the generator on and press the Boost switch...then you are good to go.

BTW, I had to take it off twice (be SURE to label those two little wires as to which is which) because they installed a new regulator and left it at the setting for a wet cell. When my VMSpc showed me it was charging over 15 volts, I knew I had to get it back off and adjusted down. It was so easy, I removed it in the alley behind the electric shop in downtown Kearney and they reset the regulator (internal) to 14.1 to keep my Gels happy.

Re: Can I replace my alternator?

Reply #6 – July 25, 2014, 10:54:43 pm

Based on my experience this last April (and the $146 bill) I strongly recommend you periodically check and clean the contact points on your alternator. Dirty, corroded contacts can make your alternator seem to be shot.

Re: Can I replace my alternator?

Reply #7 – July 25, 2014, 11:58:21 pm

I'm trying to figure out where the sootiness is coming from?
Is the soot oily or more like a powder?
If oily, the only source would be the bearings which I wouldn't think would have that much in them. Maybe its metal (aluminum and/or steel) powder from dry bearings?
At the very minimum I would pull the belt off and turn the alternator by hand to feel if the bearings are smooth. When most alternators go out the bearings are still good and you can continue traveling with boost switch on and generator running. But if the bearings go then the belt has to come off and you loose whatever else is on that belt; I can't tell what the pulley does that's between the tensioner and the alternator; water pump? That will leave you stranded.
If a powder I would think the brushes are about gone. I would pull it and have it rebuilt.
I guess I'm in the proactive camp here. Why wait and run the risk of messing up your travel plans? It does look like something going on with it.

Re: Can I replace my alternator?

Reply #8 – July 26, 2014, 12:45:00 am

What do you mean by 'contact points'? Where are 'contacts'?

Re: Can I replace my alternator?

Reply #9 – July 26, 2014, 12:58:51 am

Could well be as John has posted. Good idea to pull the belt and check bearings on alt and idler as well as the belt itself. With the right breaker bar, you can do it all in a couple of minutes.

Black dust could also be from a slightly misaligned belt rubbing on the pulley edges and sending sticky rubber dust onto the face of the alternator.

Nice to know everything is working well and not having to rely on generators or boost switches if things go south.

Pierce

Re: Can I replace my alternator?

Reply #10 – July 26, 2014, 09:03:04 am

Pierce.......How do you align a belt? I had my alternator rebuilt and they replaced the pulley. Now the belt seems to want to walk towards the front of the motorhome and rides on the forward most ridge of center pulley. Also put on a new idler. How much should that bounce? I shimmed the alternator towards the rear of the motorhome thinking that would move the belt away from the pulley ridge it was riding on. At $45 each I don't want to replace the belt every 200 miles.

Twig

Re: Can I replace my alternator?

Reply #11 – July 26, 2014, 11:32:55 am

Twig,

Flat serpentine belt installations usually have a spring loaded tensioner with a idler roller as part of the tensioner. Your problem can't be solved by moving the alternator but by making sure all pulleys and related parts are not only aligned with each other but more importantly, each one has to be in the same vertical plane. Our tensioner pulley was off 3 degrees vertically and caused the belt to ride on the outside of crankshaft pulley where it frayed and failed on a regular basis. It happened to the previous owner and left him stuck by the side of the road and after we picked up ours, it also failed a few days later while we were on the way home. Because of the steering wheel position in relation to the warning lights on GVs, I did not see any lights until the engine went into shut down mode. A big design flaw.

Wish I could find my previous post but basically, you buy a $5 angle finder at the hardware store or Home Depot, etc. The coach can be at any angle. Just place the angle finder on the face of each pulley and compare each reading with the angle finder pointed vertically. I had to put a shim (I used a washer) under one side of the tensioner to get it to match angles. It was 3 degrees off. You also need to put a straight edge across the face to make sure they are all aligned with each other so the belt takes a straight path.

So, when the tensioner is at a different vertical angle, it causes the belt to try and go sideways and take a slightly different path. It does this many times each second. After it goes a few hundreds of an inch, it jumps back to the original position and causes the pulley to jump up and down when it does this. It also causes the pulley to deviate from it's path on the crank pulley and start to ride on the side/lip where it start to fray after either a few or many miles depending of the amount of misalignment. Many have thought their tensioner was bad and replaced it. Once the alignment is correct, the bouncing at idle will stop.

Tensioners have a square hole in them and either a 3/8" or 1/2" breaker bar will enable the arm to be moved and the tension released so the belt can be removed.

At least two spare belts for each location should be carried onboard. You can save close to half by ordering off the internet as they cost an arm and leg at the parts store plus they may not have the correct belt in stock. I recommend the Gates Fleet HD Green Stripe belt. They cost $10 more at the parts store but only a couple of bucks if you order online. The only thing tougher are supercharger belts and they cost over $100/ea.

A belt with the same number of groves as the pulley should be fitted. Foretravel recommended the wrong 6 rib belt for our U300 when the pulley has 8 ribs. The belt should ride in the middle of the idler/tensioner roller within 1/8". Our Toyota RAV4 has a 7 rib serpentine belt with 160K original miles and still in good shape.

The crank pulley is stationary but the pulleys on the accessories can be moved on their shafts or the entire mount moved a little fore and aft.

Every so often, it's good to take a few seconds and use a breaker bar to pop the belt off so you can spin the alternator and tensioner pulley to check for dry bearings. Only takes a few seconds. Also applies to the hydraulic pump/tensioner/hyd motor.

The photos below are for a hydraulic pump but the alternator is done the same way. I used a ratchet in the photo to show belt removal but a longer breaker bar makes it a lot easier. The closeup of the tensioner shows the small washer at the end of the arrow. Hard to see but was just right to make the 3 degree correction.

Pierce

Re: Can I replace my alternator?

Reply #12 – July 26, 2014, 05:27:48 pm

UHHH, by contact points I meant the "points" where the electrical cable ends make contact with the output terminals and nuts on the alternator. Corrosion will decrease "contact" between "points" that have to have excellent surface transfer capability or the alternator will seem to have gone "bad" and yet might only need the points of contact cleaned.

Re: Can I replace my alternator?

Reply #13 – July 27, 2014, 08:40:52 am

Pierce, excellent explanation and thanks for the photos. Always enjoy your comments.

Larry

Re: Can I replace my alternator?

Reply #14 – July 27, 2014, 09:05:02 pm

Depending on where your engine exhaust dumps out, the black soot could be being inhaled from your exhaust. The only electrical parts that may need to be replaced would be the brushes. Depending on the size of the present alternator, you may want to upgrade to a higher capacity one. I changed out my 105 amp alternator for a 160 amp one. The consideration being that you can handle a larger load (inverter mainly) when running down the road. Have a great day ---- Fritz

Re: Can I replace my alternator?

Reply #15 – July 28, 2014, 02:49:55 am

Quote from: fkjohns6083 – July 27, 2014, 09:05:02 pm

Depending on where your engine exhaust dumps out, the black soot could be being inhaled from your exhaust. The only electrical parts that may need to be replaced would be the brushes. Depending on the size of the present alternator, you may want to upgrade to a higher capacity one. I changed out my 105 amp alternator for a 160 amp one. The consideration being that you can handle a larger load (inverter mainly) when running down the road. Have a great day ---- Fritz

Im not a expert at all but my general knowledge seems to say the alternator output needs to be matched to the batteries ability to take the charge? My coaches batteries take 130 amps of 12 volts cd into the house batteries from the inverter/charger. Plus a trace from the equalizer into the three engine batteries if needed. A 165 amp alternator might be capable of over charging the batteries max input rate.

Unless of course you have three house batteries? Or more? Any idea of the actual inverter draw off the motor?

I have put dual alternators on coaches before to run a constant output into an inverter to run roof airs going down the road. Expensive. $4-$5k setup then. 4-5k watts output. Separate from the coachs itself alternator.

Yes the coach slowed a bit when on. This was in the days of gas or propane gen sets.

Gallon an hour to run the propane gen. And 58 gallon capacity

Re: Can I replace my alternator?

Reply #16 – July 28, 2014, 10:25:56 am

Bob,

Alternator CAPACITY is really not a factor in matching to battery bank size unless you routinely use the alternator after dry camping to recharge them. Even the 190 amp alternator with a single 8D battery will not overcharge it. The regulator controls charge rate.

The advantage of a larger alternator/larger frame is that it can give you higher charge rates without overheating.

Re: Can I replace my alternator?

Reply #17 – August 27, 2014, 03:58:19 pm

If it goes out on the road be very careful having a truck shop fix it. They do not understand the isolator in motorhomes. I lost two days on a trip cause they couldn't figure out how to get the replacement alternator to charge (mine is externally excited). They ended up jumping two of the posts to make it charge. It worked but defeated the boost switch by permanently linking the two batteries. I ended up changing it to the correct one myself but discovered no wire to connect to the additional post that needs 12v with ignition on. After examining the nearby wire loom I found some electrical tape and after removing it discovered they had cut that wire (that had 12v whenever the ignition was on) which was needed for the additional post on this style of alternator. Big rig alternators are not typically used on applications with a battery isolator.

Re: Can I replace my alternator?

Reply #18 – August 27, 2014, 09:25:29 pm

In spite of having a generator and the boost feature, if a bearing goes away, you are dead in the water until it's replaced.

Easy enough to carry spare bearing though if you don't care to take the preventive route. pc

Re: Can I replace my alternator?

Reply #19 – August 28, 2014, 08:37:14 pm

Quote from: pocketchange – August 27, 2014, 09:25:29 pm

In spite of having a generator and the boost feature, if a bearing goes away, you are dead in the water until it's replaced.

I don't think that's the case with the M11 in our 1995 U320. The alternator is driven by a belt that drives only the alternator. I think that belt could easily be removed and nothing else would be affected.

Affiliate Notice