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Old 09-01-2013, 08:30 PM   #29
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Thanks everyone for the great replies! I am going to take my old alt to the elec shop and see what they can do for it. It would be nice to have a backup just in case.


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Old 09-02-2013, 05:57 AM   #30
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I'd be curious as to what failed? Depending on what it was, might give you some guidance on potential issues with the new one?

1997 37' HR Endeavor, 275hp Cat, Freightliner
03 CR-V Blue Ox, Ready Brake
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Old 09-02-2013, 01:57 PM   #31
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Our coach is new so we shouldn't have any failures soon, at least we hope. Keeping a spare is a great idea.

As far as a rebuilt AL. Words are just that WORDS. Re-built, re-man, re-furb etc, etc. It means ABSOLUTELY nothing. There is no guarantee that one is better than another UNLESS you look at three things. Who is doing the work? What is the guarantee? What is the price?
PARTS HOUSES & REBUILDERS: If F*B*N (Fly-By-Night) alternator re-builders is doing the work then I'd worry. If you know of a shop that is old-school then they should have a reputation that you can check from some of the locals. If you have to use a parts house it is probably not wise to use a local Mom & Pop parts house. They just don,t have the support that the larger chains do. As I've said before I use NAPA. They are Nation-wide. They have a reputation to uphold. In this area O'Riley's is big in this area and they are OK. Don't forget these people also use re-builders for items like these: alternators, starters, CV-axles, Rack & pinion steering units, etc,etc.

GUARANTEE: Almost any parts house will sell you re-built units with different guarantee's. Why is the best guarantee more?? Because it takes more time and parts. They check everything and replace if needed. They will also load test the better rebuilds to check for a quality sine-wave, and over-load it some to check for electronic parts quality.

PRICE: Usually price tells you that it took more parts, time and skill to do the rebuild. that also translates to better quality and longevity.

If I need a starter, alternator, I will buy the best from NAPA. If it fails I can get a new unit anywhere in the country from at least AR to Maine. I don't know about west of here.

WHY ALTERNATORS FAIL??? I'm not sure about the charging of dead coach batteries as a cause. Lets see: You drive your car day and night. Place a good load on it from all the current drains especially in the winter, heater blower, lights, radio, electric defrost etc, etc. and they seem to last.
During your cars run/charging time you use the AL, electronic regulator etc, etc and it last a long time.

You drain your coach B+'s, leave the CG and head down the road. The Engine is running draining your engine B+. The coach B+'s need charged. So the alternator puts out what it can to recharge everything. It's using the electronic voltage regulator, stator windings, rotor, etc and it's working. I don't believe it is much more of a load than any car deals with on a regular basis. They are designed to provide a charge to dead B+'s. I don't see a significant difference in adding 2 or 4 more B+'s to the alternator work load. It's not going to provide 30-50-amps of current to re-charge the coach B+'s. It will provide a slow trickle charge and it will take a longer period of time. Just because it has 6 B+'s to charge does not mean that it is being asked to over-load itself. It will charge for a longer period of time.

Common sense tells me yes maybe a little more work load but not enough to really shorten the life of the alternator by much.


TeJay (Tim) Auto Instructor 35 yrs (4-yrs USAF) Liz: RN/ WBGO 2014 Vista 30T/ F-53/ CHF/5-Star/Koni/Centramatics * Bella- Golden/Cocker mix & Louie-The cat / All Retired
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Old 09-02-2013, 07:37 PM   #32
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It's very possible for anyone repairing an alternator to call it a rebuild, we agree on that I think. Whether or not it actually has been, and to what degree, may or may not have a thing to do with what's charged for it in my way of thinking though? Assuming a more expensive part is higher quality is frequently not in your best interest, UNLESS those factors that make it higher quality are spelled out in black and white using plain english? Otherwise, all you have to go on is reputation - which is of little or no use when more than a few miles from where you got it.

Re: what made it quit, high loads on parts that aren't making good contact, like corroded or otherwise crudded up brushes not sliding properly up against slip rings, overheated electronic components, like diodes and voltage regulators, that's what generally takes them out in my experience, or maybe high mileage that might take out a bearing?

Re: a car or pickup alternator? I think the level of engineering, QC, testing, and a host of other reasons make comparing those to a MH installation like comparing apples and oranges. Some of those even have liquid cooling with anti freeze running through them for cooling?

The level of engineering in the average MH install is a question of fit and cost, little else?
1997 37' HR Endeavor, 275hp Cat, Freightliner
03 CR-V Blue Ox, Ready Brake
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Old 09-02-2013, 07:48 PM   #33
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Originally Posted by rebelcarm View Post
Do not know what coach you have? I had 3 alts go on my last motor home with a rear rad.Only had total about 60000 miles. This RV has a side rad seems that cures the problem, have had no failures to date, have traveled over 40000 miles.So far still has original alt. If you have a rear rad, heat seems to be what ruins the alt., Just my 2 cents worth.
Our alternator went out a couple years ago. Finally got around to replacing it earlier this year.
Had about 33,000 miles and was on a side radiator unit.
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Old 09-02-2013, 08:01 PM   #34
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Points well taken. My reason for mentioning reputation and cost you kind of agreed with. If a parts house is large enough then usually they do have more of an obligation to stand behind their parts. They do have more to loose if they start selling junk. The local repair facilities will stop using them and that hurts business.

Here's another reason I like NAPA. Years ago I went to the local dealer and they gave me a CD on brakes. Yes it did advertise some but the information in there was priceless. It talked of quality cast iron and the differences in it. How some companies may reproduce a rotor but they try to get one design to work for more than one car and that's won't always work. There are dozens of differences in vented rotors. It cheaper to stock one that works for several rather than stocking the exact part.

My point is that NAPA took the time and $$$$ to produce a CD to give out great information so those willing to use quality parts will stand to get better results. Sure they made $$$$ but that's what business is all about.
Most of these parts houses will always offer a cheaper line of products because they don't want you walking out without buying. If they hear a price of $76 for a set of pads that are better than OEM they might walk out. So thy offer the cheaper lines because if they don't buy their cheaper stuff they'll buy it down the road. It's tough to fix STUPID.

There is one parts house that sells a life-time guarantee disc brake pad. That is true. What people don't realize is the pad is so hard that it will wear your rotor before the pad is worn and they won't replace the rotor.

I have a friend owns a local shop and does excellent work. He was asked to install an AC compressor that a customer brought in. He said he would but if it was defective he'd charge the same to do it again. It took 3 AC compressors from a cheap house before one worked. That saved him a bunch of $$$$

I realize that there is no perfect guarantee and paying more is also not a guarantee but paying more and getting a longer guarantee from a house that sells at least from AR to ME does make sense. I bought an alternator in AR and it went out in ME and I got a new one in ME. In cases like this an initial higher cost is reflected in a longer guarantee and replacement if needed.

TeJay (Tim) Auto Instructor 35 yrs (4-yrs USAF) Liz: RN/ WBGO 2014 Vista 30T/ F-53/ CHF/5-Star/Koni/Centramatics * Bella- Golden/Cocker mix & Louie-The cat / All Retired
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Old 09-03-2013, 07:34 AM   #35
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The alternator on my coach has a very poor track record!

The 1st alternator failure was at 78k miles, (9 yrs).
The 2nd, (a rebuilt), failed 4 yrs, 23k miles, later, (when a a spade wire connector, on the internal voltage regulator, corroded/broke off).
The 3rd, (also a rebuilt), failed 3 yrs later, (after another 25k miles).
The 4th, (a rebuilt, from a local reputable alternator/starter rebuilder), has only been on for 6k miles, (1 yr).

I also carry a repaired, (not rebuilt), one as a spare.

'96 Safari, 132k miles
rear radiator Cat,
Delco 130a 21si alternator
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Old 09-03-2013, 01:30 PM   #36
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Design and quality

These both are required.

Design, quality of the design, and build to the design.

So what does it mean?

THe manufacturer designs the RV with a factory chassis, but knowing it will have two battery systems later, the RV manufacturer requests a larger alternator, say 100 amp.

THe original design has a group 27 statring battery as well as a group 27 coach battery.

Starting battery usually does not need deep charging, so fair current for short time.

Coach battery is discharged deeper, so requires higher recharge rate, this is limited to the capacity of the alternator and the resistance of the battery.

Can take every bit of power the alternator can produce.

Self regulating...?

Okay the regulator for the alternator is based on the voltage of the starting battery, depending on how the chasis is wired, the regulator can look look at the engine system, so the alternator will be trying to output 14.5 volts, combined with a dead coach battery the alternator will be running full output and then some so to speak.

Now the user replaces the group 27 battery in the coach with two six voilts ones, now has 220 or so amp hours of battery...

THe usual full charge rate of most batteries is 1C, where C is the labeled capacity, so we now have a 220 amp load on the alternator...

They charge at this high rate for a short period of time then the rate decreases as they go from bulk to next phase.

So before we blame the poor quality of the alternator we need to look at the system and see what the heck is going on.

Given the duty cycle of the battery systems and how we plan to restore the charge to the batteries the alternator is likely undersized for the use.

A larger one may be needed, a different type of isolator may be required, secondary charging via the converter powered by the generator may be needed.

Ours has a 150 amp alternator, 2 sets of 8D with a GP 31 in the front.

Alternator does not produce full output until highway speeds so the setup time to fill the air systems and just idleing the engine produces lower output for the alternator, the regulator turns it on 100%, but at low speed the output from the alternator is no where near the capacity of the alternator so the stresses on the components are minimum.

It is charging the batteries, just at a lower rate.

It may be units DP have larger alternators and due to the need for idle before departure there is less stresses on the units where gas models are start and go, and combined with higher engine RPM the alternators are more likely to be at capacity more of the time.

Now I could be full of it, but it may make some difference in the operation.

Tony & Lori
1989 Country Coach Savannah SE
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