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Golfer Guy · 04-12-2015, 09:23 PM

Have an 06 38' Beaver Monterey 400hp cat. Coach is new to me and I have been working out all the kinks I have found.

After boondocking for the past several weeks I had the alternator reading at 14 V and then after a minute or so it went to 16 V. The Aladdin now shows anywhere from 15.5-16.3 V. This is also causing the inverter to show a red light and a reading that says high battery.
Yesterday I replaced all six batteries 4-6v house 2- 12v chassis. And still the same alternator high reading. The batteries are full charged.

Also I have a new Big Boy ordered and will replace that as soon as it arrives. I have been concerned some of the low battery issues I have been having have been caused by that relay. However the more logical answer is that it has probably been more of a low battery issue I have had with the old weak batteries.

Now the question is what could be causing the higher than normal alternator output and what issues will that create. Is a new alternator needed?

Wish I was more electrically minded.

Thanks for your thoughts

Dr4Film · 04-12-2015, 09:33 PM

Do you have a DVOM meter or even just an old analog meter to make some voltage readings at the House and Chassis batteries?

To see if the alternator is actually outputting that high voltage I would verify it first with a meter hooked up to the Chassis battery.

Take a reading with the engine off and then take another reading with the engine running.

Dr4Film ----- Richard

Golfer Guy · 04-13-2015, 08:56 PM

Had the alternator checked and will be replaced tomorrow. Hope to have the new Big Boy tomorrow too. Get that in and should be good to go.

Randyman1 · 04-14-2015, 11:40 AM

Golfer Guy, something to consider in the future that I have learned on this forum is to start with charged batteries whenever possible. Like plugging in the night before you leave on a trip, or if boon docking run the generator before heading out. That lessens the load on the alternator from having to charge low house and chassis batteries. Extends the life of the alternator by not overheating it. JMO Randy

TeJay · 04-14-2015, 12:04 PM

Golfer Guy,
When you said you had the AL checked what did you mean???? Dr4film asked if you had a DVOM and to check the battery voltage at rest then with the engine started. Maybe you did check the voltages and decided to have the AL replaced. If you took it in then somebody else decided that it needed replaced.

Here's my concern. Some reading this thread might want to know why and how?? If you don't then stop reading.

As far as I know every 12-V system that uses alternators (AL) to stay charged work with the same goals in mind. They will re-charge your batteries and always maintain at a charging voltage of at least 1 volt above the resting voltage. So a battery at 12.6 -V will show a charging voltage of around 13.6-v or slightly better.

1. If your resting or (more correctly referred to as, "Open Post battery voltage") is 12.6-Vs that's means that it is a fully charged battery and is just fine.

2. Now when you crank the engine to start it a lot of current (150-AMP LOAD) will be drained and therefore will need to be replaced. So after starting the "Charging voltage from the AL should be at least 13.6-13.9v's.

3. If your charging or engine running voltage is not at or above the 13.6-V there is a problem. One can assume that the AL is bad. That's a decent assumption but what if a rodent ate a wire??? I'd assume the AL is bad also but???? Maybe the electronic voltage regulator is bad. They are inside the AL so these days it's easier to just get a replacement which you apparently have done.

4. If on the other hand the voltage is above 15-V's or even 16-V's that's way to high and will overcharge the batteries and perhaps boil the water out of the battery. Signs of a defective regulator.

The skills needed to diagnose a defective AL are minimal. Just follow the procedure outlined and you'll know what you have. What's going to happen if you're in a CG and encounter the same situation. Wouldn't it be nice to really know what's wrong with the charging system. Making these voltage readings is very elementary and extremely helpful. I'd rather trust my diagnostic skills then to rely on some repairman whom I don't know tell me I need a $300 alternator that I may not really need.

This really did happened!!!! Years ago a friend wanted to go to CO with his WBGO but his AL was not working all the time. If he idled the engine it charged. If running down the road it would not charge. A full 10 hours of testing revealed nothing. I was not involved but my friend the other auto teacher was. So spring break came and he took off to CO. They drove for several hours then stop in a rest area and re-charge the batter at idle. They did that all the way out and all the way back (900 miles each way).

After he got back home they did some further diagnosis and guess what the problem was all along???? The alternator belt was loose. At higher RPM's and more load/drain on the AL the belt slipped. Get it back to an idle with low drain and it was tight enough to recharge the batteries.
Diagnose, diagnose, diagnose. (I love that story!!!)

TeJay

Golfer Guy · 04-14-2015, 12:11 PM

Quote:

Originally Posted by Dr4Film

Do you have a DVOM meter or even just an old analog meter to make some voltage readings at the House and Chassis batteries?

To see if the alternator is actually outputting that high voltage I would verify it first with a meter hooked up to the Chassis battery.

Take a reading with the engine off and then take another reading with the engine running.

Dr4Film ----- Richard

Yes I did test the chassis batteries at rest and they were 12.4 I believe. Also tested the alternator when running at the back of the alternator and it was anywhere from 16-17V. Therefore I have ordered a new alternator and will install today or tomorrow.

Thanks for your input.

TeJay · 04-15-2015, 06:37 AM

Golfer Guy & Richard,
Good!! I'm always happy when correct diagnosis leads to the lowest repair costs. That has always been my goal on these forums. Do let us know the final outcome.

TeJay

Steve Ownby · 04-15-2015, 06:56 AM

Quote:

Originally Posted by Golfer Guy

Yes I did test the chassis batteries at rest and they were 12.4 I believe. Also tested the alternator when running at the back of the alternator and it was anywhere from 16-17V. Therefore I have ordered a new alternator and will install today or tomorrow.

Thanks for your input.

From reading lots of these "alternator" threads, it's apparent to me that its exceedingly difficult to get the correct alternator as a "drop in" replacement for our coaches. You might consider taking your old unit to a rebuild shop & having it rebuilt. This would give you an immediate replacement if you have an issue down the road.

Steve Ownby
Full time since '07