Repeated alternator failure

Ol'Reggie wrote:
I got a new isolator ordered today, I'll let you know how it goes when it comes in.

YES! Please Do! What you got, and how you wired it.

Fords HAD all the problems I outlined earlier in this thread, that's for sure. The separated regulators weren't all that reliable. I moved ours so I could change it roadside without having to lift the battery out. We had the 60A, mounted on a bracket shared with a Smog Pump and it all had to come loose to get the long alternator bolt out. It was longer than the clearance to the radiator! And, that "Side Terminal" design with the plug was a disaster. I carried spare Alternator, Regulator, Starter, Coil, and Ignition Module. If I remember, changed Regulator twice, Starter and Coil once each.

So, from my experience, I'd've been on the track the shop was. I like to hope I'd've done more troubleshooting, though. Really glad the guys suspecting Isolator got involved.

YC 1 wrote:
Please look at my post closely. As I suggested, replacing a bad component will clear up many seemingly strange symptoms.

The high voltage is because it is a pulsating DC versus a pure DC. You probably have heard the difference between pure sine wave inverters versus modified sine wave inverters.

Your meter is reading the peak voltage. Once the Alternator output sees the battery load because you bypassed that isolator section the voltage was not only loaded down properly, it is also being filtered to resemble a pure DC voltage.

What I need to know is what the voltage is now on each battery bank at the battery terminals.

If it is not the same on both banks, pile all of the isolator wires together to bypass it completely and recheck. Both outputs from the isolator could have failed at nearly the same time. It really doesn't matter because you have already proved the isolater is bad.

Thanks YC 1, you nailed it! I already pulled the isolator this afternoon, took all of about 90 seconds (grrrr, thinking about how much money I spent on mechanics diagnosing and replacing alternators). Anyhow, I checked the voltage at the chassis battery isolator post and terminal, but I had only checked the house battery post, not the house terminal.

I got a new isolator ordered today, I'll let you know how it goes when it comes in.

navegator wrote:

One area that has not been mentioned is the wiring as I recall the RV is older and that leads me to believe that in the past maybe a battery terminal might have had corrosion, has anyone checked the actual wires both negative and positive for corrosion down the cable, copper wires tend to turn to liquid and impede current flow, another point is any one checked the negative cable at the point where it attaches to the frame corrosion at point of contact is likely, then there is the ground connection between the frame and the engine it is a point of corrotion.

Last but not least if there is a separate voltage regulator, has it been checked at all, it seems to me that the mechanics that have "repaired" this unit do not know much about the workings of the electrical system in vehicles and are throwing parts in order to solve a problem, instead of checking everything and then rendering a diagnostic that is real and actually finding the cause of this problem.

navegator

Definitely will check the wiring, good call.

The new alternator does have a built in voltage regulator and seems to be maintaining the battery well with a reading of 13.7 - 14.2.

Thanks for the tips!

navegator wrote:
Two batteries and two alternators in such a short time means that the problem continues.
navegator

Actually 4 alternators! Both shops had put in an alternator that they thought was faulty (reading 12 volts at the battery) so replaced it with another that they claimed worked.

I wouldn't be surprised if all of those alternators were just fine and that the problem was the isolator all along!

Please look at my post closely. As I suggested, replacing a bad component will clear up many seemingly strange symptoms.

The high voltage is because it is a pulsating DC versus a pure DC. You probably have heard the difference between pure sine wave inverters versus modified sine wave inverters.

Your meter is reading the peak voltage. Once the Alternator output sees the battery load because you bypassed that isolator section the voltage was not only loaded down properly, it is also being filtered to resemble a pure DC voltage.

What I need to know is what the voltage is now on each battery bank at the battery terminals.

If it is not the same on both banks, pile all of the isolator wires together to bypass it completely and recheck. Both outputs from the isolator could have failed at nearly the same time. It really doesn't matter because you have already proved the isolater is bad.

Two batteries and two alternators in such a short time means that the problem continues.

One area that has not been mentioned is the wiring as I recall the RV is older and that leads me to believe that in the past maybe a battery terminal might have had corrosion, has anyone checked the actual wires both negative and positive for corrosion down the cable, copper wires tend to turn to liquid and impede current flow, another point is any one checked the negative cable at the point where it attaches to the frame corrosion at point of contact is likely, then there is the ground connection between the frame and the engine it is a point of corrotion.

Last but not least if there is a separate voltage regulator, has it been checked at all, it seems to me that the mechanics that have "repaired" this unit do not know much about the workings of the electrical system in vehicles and are throwing parts in order to solve a problem, instead of checking everything and then rendering a diagnostic that is real and actually finding the cause of this problem.

navegator

Ol'Reggie wrote:

The alternator was working, albeit a little too well at 28 volts!

Not unusual if it has ZERO load on it.

Alternators/regulators are designed to have a battery attached 100% of the time. It provides a load and some filtering.

Go to a better shop. Those monkeys and clowns are just throwing parts at it.
Get to a national chain or the dealer that will provide a warranty.

Working night shift last night, thanks for all the great advice while I slept this morning!

I rechecked everything this afternoon when I got up. Alternator post at the isolator was receiving ~ 28 volts, house battery post at the isolator was receiving 28 volts but chassis post at the isolator as well as the battery terminals themselves were at 12.05 volts. Because the reading at the battery and the chassis battery post on the isolator were identical, I assumed that the continuity of the wire was intact.

The alternator was working, albeit a little too well at 28 volts! I moved the chassis battery cable to join with the alternator cable on the alternator post in order to bypass the isolator (and crossed my fingers that I wasn't going to fry my battery with 28 volts!)....

13.7 volts!!!!!!!!! I took Ol' Reggie for a bit of a drive, and measured 14.2 volts at the battery terminals when I got back. All three posts on the isolator are now measuring 14.2 volts as well. Honestly, that part does confuse me a bit - why was there no charge coming through the chassis battery post before, but no with no wire hooked up to it, it seems to be ok? Maybe too much resistance with the battery hooked up?

Anyhow, the mystery seems to be solved, just wondering if my alternator was ever bad in the first place. Hopefully, this post will help others trouble shoot a possible isolator failure rather than shelling out $$$ to replace alternators!

Ol'Reggie wrote:

It seems clear that the alternator is not the problem - 2 new alternators charging at 12 volts?

It seems pretty clear to me that just the opposite is true: That the alternator IS the problem.......unless the new battery has a major fault, like a shorted cell or an open internal connection.

The other possibility is that none of these mechanics realizes that on a model that old, the REGULATOR might be a different unit and not a part of the alternator like is always true now.

If there is an electric motor shop in your area they should be able to sort this out quickly.

Most modern automotive "mechanics" don't know beans about electricity.