Jumping voltage

[Tom Chace]

Hi everyone,

I have a new alternator in my 99 Montery
Problem is the voltage is going up to max +/- 16.5 V then drops - then goes back up again

Does anyone have suggestions?

All grounds have been cleaned and some cables have been replaced................
I haven't checked the coach batteries which is coming next  BUT I am running out of ideas........

Thanks
Tom

[Tom Chace]

help needed

[Steve Huber Co-Admin]

Tom,
What is your battery condition? A bad battery may give this symptom. Also, where are you reading the voltage; at the house or chassis batterie, on the analog dash gauge, or on the Silverleaf? If not a battery, could be a faulty voltage regulator.
Steve

[Gerald Farris]

Tom,
If the voltage readings that you posted are accurate, you probably either have a bad connection in your sense wire to the alternator, or a bad voltage regulator.

Gerald

[Tom Chace]

Ok guys

I am going to test all battery cells again tomorrow And will check the regulator

This is a new alternator/regulator.

Gerald, What/Where is the sense wire


Thank you
My departure date is coming soon and need to get this resolved

May be late to the sunshine and warm but hopefully not TOO late

Tom

[Tom Chace]

Steve,

I forgot about your question

The Chassis batteries are <1 month old
The Coach batteries are years old

Could the voltage selection / isolator switch also be suspect?

[Steve Huber Co-Admin]

Tom,
Don't know how the isolator switch could cause the symptoms. If your batteries are OK but aren't fully charged, use your generator to charge them and then see what the alternator voltage does. If it still surges, it's probably the sense wire as Gerald suggested.
Steve

[Gerald Farris]

Tom,
The battery isolator on your coach is not a switch, but it is just a very large diode that separates both battery banks, and prevents either battery bank from supplying battery voltage back to the alternator over the alternator output cable. Therefore, a sense wire is needed to supply battery voltage to the alternator regulator. Without this sense wire, the alternator does not know what the battery voltage is, and this usually results in overcharging the batteries.

There are 4 wires that are attached to your Duvac alternator. The large wires are for alternator output and ground. One of the small wires is ignition, and the other small wire is the sense wire. The sense wire has battery voltage on it at all times, but the ignition wire is only has voltage when the ignition is on. If the small wires are reversed, the alternator will cause a drain and overcharge the batteries, so be very careful that all wires are on the proper terminal. The sense wire usually runs from the chassis battery positive terminal or from the chassis battery post on the battery isolator to the sense terminal on the alternator.

Gerald  

[Tom Chace]

I AM NOW WONDERING

What alternator was stock on my coach?

1999 Beaver Montery w/ 300 CAT

The alt that was on it was a  110-555JHO OEM Alternator Leece Neville 160 amp J180 Alt 110-555 12V.
Is this the correct alternator?

This is also the replacement on it now which is when the voltage started this jumping


TIME LINE
The batteries were draining for a while.
I replaced the chassis batteries
They would not charge due to the alternator malfunctioning. They do charge through 120 v and solar.
I had the alternator checked - found a problem - replaced the alternator with the same alternator
The voltage started jumping shortly after
Cleaned all connections and grounds both by me and the mechanic .
Mechanic has had a problem with the voltage jump cause and has been looking for a while

I am about out of time and patience



Thank You

Tom

[Gerald Farris]

Tom,
I would call Leece Neville technical support at (800) 354-0560 if you are in question about having the correct alternator.

Gerald

[Gerald Farris]

Tom,
I just looked up the alternator that you listed above, and it is not a Duvac alternator. So if your coach is wired like I described above, it is not the correct alternator. However, a knowledgeable electrical mechanic can rewire the coach to make it work.

First you need to determine how the coach is wired, and if it is wired with a battery isolator like I described above, you need someone who is very knowledgeable in automotive electrical systems to rewire the coach or install a Duvac alternator like the 2824LC.

If your coach has been rewired to use a solenoid as a battery isolator or had a "Bird" system installed, the truck alternator that you have will work. There are several coaches that have had their electrical system rewired to use the cheaper truck alternators instead of the Duvac units. How is your coach wired?  

Gerald  

[Tom Chace]

Gerald,

That alternator was in the coach and working so I believe the system was / is rewired.
Unfortunately, when I purchased the coach this is the system in it.
It worked fine until it didn't.

I have had the coach at the mechanics and just heard that he found the problem.

We will see.

T