Alternators

[Just Plain Jeff]

This likely is going to get into a can of worms, but never one to walk away from such things...

1. Finding high output internally regulated alternators is a tough gig. Various converters use different alternators with different brackets which are difficult (sometimes) to find. If you look on the internet, you'll find that there are Delco-Remy 145 Amp HO, internally regulated alternators, but they have a limited lifetime as they are designed mainly for diesel pickup trucks. The Lees Neville, a 180 amp HO, internally regulated alternator is what you want. However, it is important to carefully check the custom bracket upon which they are mounted. These are typically custom-made and not often made well.

2. If you are replacing house batteries, this is a great time to check the alternator. An alternator should not be putting out full charge all the time...the idea here being that an alternator should charge/rest/charge/rest, you get it. If the house batteries, for example need replacement, it is possible that the alternator may be cooked or on its last legs.

3. The famed DN/50 alternator, found mounted on the front of OTR 8V92 coaches has a lifetime of about 150K miles. Usually the bearings go on them first. If someone tells you that they can 'hear' that it is good, start talking with someone else. These alternators are huge 24 v, three-phase puppies, driven from the camshaft and lubricated by the oil in the engine. In most cases, they are replaced from above, requiring the bedroom flooring to be opened (although they can be replaced from below).

4. Some coaches are dual alternator coaches: One for 12v, the other alternator for 24v.

Alternators (excepting the DN 50 can easily be checked for output. When the DN50 goes, you'll know it.

So there you go as a couple of comments about alternators.

Let the games begin.

[Jon Wehrenberg]

Good information and a few minor corrections. The large front mounted alternator on 8V92 engine coaches may likely be 12V. It charged the bus batteries which are two parallel sets of series connected batteries, and they are charged at 12V through the equalizers. When the 12V charging circuit is energized it powers a relay which is normally closed to extinguish the red light on the dash. It is the appearance of the red light that tells you of a problem and it is not necessarily that big alternator. The field wire between the alternator and voltage regulator was sometimes too short and broke at the alternator. The failure could also be the voltage regulator.

If however the alternator fails, it is possible to remove it from beneath the coach without gaining access from above. When Willie was with Prevost in Lyndhurst he would raise the coach up far enough so his head was at about the same level as the alternator. From this position he could twist his arms around sufficiently to access and loosen all bolts. He would then change the height of the coach so he could slide the alternator toward the front of the coach over the transmission and then down along the driver's side of the transmission. No matter how it is accessed the alternator is in a lousy position for removal, and a lot of oil leaks and drips. For that reason he would remove it from the bottom rather than risk soiling the coach interior.

[Just Plain Jeff]

Waaalll, the DN-50 is a 24 volt 3-phase bugger; the means by which the power is distributed can be different on some conversion coaches, as they rewire (such as in Liberty's case) the 24 volt feed system. Others do not. To further complicate matters, some folks have taken to choose the system you are explaining, while others (few) rewire the system to an electrical 'bus' system.--->Update: I just checked and the alternator actually is a 12/24v unit. In our previous campers, both were 24 volt for the OTR system<--

I don't rely on red lights to check the condition of the bus. Rather, very detailed and attentive reading of the gauges is highly recommended. Generally speaking, once the 'red light' goes on, it may be too late to perform the necessary (which should read 'scheduled' maintenance.)

There are OSHA protocols about lifting stuff and heavy things coming down on your head. Prevost has replaced, depending upon the facility and the tech, DN 50s from above and from below. The safest and most conservative fashion to remove the alternator is from above, (usually there is a panel precut just above the alternator) with the use of a temporary tripod. The other advantage to a top removal is the ability to line up the new alternator for proper position with respect to the drive mechanism.

An unhappy camshaft-driven alternator is a bad day.

[Tully]

The DN/50 alternator- can this be bought new still or would it have to be rebuilt?

Any sources?

Tully

[Joe Cannarozzi]

Tully I do not think your alternator is bad but it is that voltage regulator on the upper engine bay with the red and orange lights both lit.

I would pull your house (inner) alternator and have it tested before you spend any money. I think when that battery lead hooked to it was shorting on the mounting bracket it fried the regulator.

Pull the regulater too when you have the alt. checked there was a manufacturers lable on it you can call them and see what those illuminated lights are saying.

DO NOT attempt to pull that alt without disconnecting your house bank of batteries first.

[Tully]

Joe:

Thanks for the FYI. I will check into both.

Can you correct me on this- was the alternator to the bottom right side of engine the 12 volt that charges house batteries? The main alternator above it was the 24 volt?

Thanks,

Tully

[Joe Cannarozzi]

The one closer to the engine is the house 12 volt.