Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 10, 2025 ...

I had a similar problem, turned out it was a $5 relay, runs from the alternator rear over to the bay wall under the bed.

You seem to have thrown lots of parts at this problem. What are you using for a start battery and what is the current voltage?
Are the battery terminals clean and the cables tight?

Try to use a logical approach to finding a solution.

In typical alternator terminology "S" does NOT indicate the "Excite" terminal.  "I" (for Ignition) would commonly indicate the "Excite" connection.  This marking may also hold true for voltage regulators, although I'm not sure cuz it's been decades since I last saw one.  See diagram below for a generic diagram of alternator + external voltage regulator.  Notice the switched ignition signal goes to the "I" terminal on the regulator.

If you believe the alternator is not getting the excite signal, try to determine why.

Try to search the alternator brand/model number online.  There are "installation instructions" available online for almost every common alternator.  If you have a separate voltage regulator, you also need the instructions for that device.

The reason you want to see the installation instructions is to identify the correct connection of wires to the alternator/regulator.  Does the alternator (or the regulator) have a terminal dedicated to a EXCITE wire connection?  If so, do you have a wire connected to that terminal?

If you DO have a EXCITE wire connected to the alternator/regulator, is that wire HOT when the ignition switch is turned to ON position?

IF the wire is HOT with ignition, then it is good.  If not, you must either replace the wire or find the break and repair the wire.

Any length of wire, or fusible link, can be easily tested for continuity with a multimeter or even a simple 12 volt test light.

.... ok.
I have a picture here of the replacement I was given for the alternator. There does not seem to be an excitement wire, unless it is coming through the sense wire.

I checked the voltregulator.  The I prong is not hooked up, and I heard somewhere it was supposed to be unhooked.  This would mean that the alternator I have should be internally excited from the belt spinning it.

Can anyone support this claim? this seems to be a carquest rebult alternator.

OK, based on your description of your alternator connections, I found the video linked below.  I'm guessing your alternator looks similar to the one in the video?  I personally learned a bunch from watching the video.  For one thing, the generic diagram I posted in Reply #22 does not exactly match this setup (connection to "I" regulator terminal is different).  Hope it helps you understand how your system works.

The video explains the meaning of the alternator combo plug connection for FLD and STR.  FLD = Field.  STR = Stator.

The Field (FLD) wire is what energizes the alternator.  When that connection on the alternator "sees" 12 volts, the alternator starts putting out charging voltage.  This, then, functions as the "excite" connection on the alternator.

The voltage regulator has 4 terminals:
"I"  =  Instrument (or Indicator)  Used to power optional idiot light on dash.
"A"  =  Battery Positive (should be HOT at all times)
"S"  =  Stator (should be HOT only when ignition switch is ON)
"F"  =  Field  (goes to FLD connection on alternator)

The wire going to the FLD plug on the alternator comes from the "F" terminal on the voltage regulator.

The "S" terminal on the regulator is connected to a "HOT with ignition switch ON" voltage source.  When this terminal "sees" 12 volts, it tells the regulator to send current down the wire to the FLD terminal on the alternator, which turns the alternator ON.

Armed with this info, you should be able to test the connections on your setup, and determine what is working and what is not.


https://www.youtube.com/watch?v=KjdaTypqj6o

1. do I have an idiot charging light in the instrument panel somewhere? when all is said and done might be nice to hook up later.

2. Does this alternator have any issue with an isolator after it instead of being a direct connect to the battery?

When I put the key into the ON position, it doesn't work. All readings are flat.

Yes, this does give me all I need to know to follow the current system.
Yes, It does look just like the alternators on hand.

The remaining two questions....

1. do I have an idiot charging light in the instrument panel somewhere? when all is said and done might be nice to hook up later.

2. Does this alternator have any issue with an isolator after it instead of being a direct connect to the battery?

1.  I don't know.  Perhaps another '87 model owner can tell you that.  If not, you could always add one yourself...

2.  Once again, I refer you to the discussion on DUVAC charging systems.  What is DUVAC?

In short, IF your alternator and voltage regulator are working correctly, the alternator will put out some amount of charging voltage.  The amount will be controlled by the voltage regulator.  Whatever the alternator puts out will go to the center post on the battery isolator, and from there it goes to the chassis (start) battery and the coach (house) battery.  In a common diode isolator you suffer a loss of slightly less than one volt between the center alternator post and the outside battery posts.  So if, for instance, the alternator sends 13 volts to the center post, the batteries will only see slightly over 12 volts, which is not enough to properly charge the batteries.  This voltage loss explains WHY you either need a specialized type of alternator (DUVAC) to properly work with a diode isolator, OR you need a way to manually adjust the alternator output to the required voltage.

There are several solutions to the "isolator voltage loss" problem...some are simple and some will cost you more money.

Question:  Does your coach have a BOOST switch on the dash?

Here is some light reading:

New battery isolator

Battery Isolator or auto combiner?

Charging both House and Start Batteries

Hello!

Here is what I have at this point.

Charged battery to 12.8

Started RV,

No apparent charging.

Voltage reads 11.79 on both the s and a post,
6.76 on the f post.

Re reading battery: 12.25

Is this enough voltage, or is there enough voltage loss to account for this?
Maybe the battery is bad.!