Forum Discussion

Boogiemachine's avatar
Boogiemachine
Explorer
Apr 22, 2020

Alternator not charging Batteries

Hey guys well figured out the voltage problem on the RV now I'm having a problem with alternator not charging the batteries. 96 Southwind with 7.5 E350 engine.

So Batteries are showing 12.3 V when the RV is running and 14.3 at the alternator. I traced the wires down to the Starter switch and checked voltage at the each lug and discovered that the second lug to the battery side isn't at 14V its at 12. Question is its definatly a solenoid can I introduce 12V to the controller lug to see if the mechanism is bad or does it take less then 12v. I also discovered the Fuse and fuse block line for the Starter Switch Coil was dead.

Any thoughts? I'm thinking it might be a computer issue. Also all battery terminals have been cleaned/relugged and all the grounds to the chassis were cleaned up


[img][/img]
Class A
  • enblethen's avatar
    enblethen
    Nomad
    Apr 24, 2020
    The ground from coach to chassis should be the same. I even installed #4 wire jumper between the two systems. Verify that the engine is grounded to the chassis frame. Many times engine/transmission work is done and the bonding jumper is not reconnected.
  • Boogiemachine's avatar
    Boogiemachine
    Explorer
    Apr 24, 2020
    So I realized the coach batteries don’t have a ground to the chassis. If I were to put an alligator clamp on a grounded part of the chassis. I get 14.2v. I got the MH from a friend that might have screwed around with the electric. Is there supposed to be a common ground for all batteries?
  • DrewE's avatar
    DrewE
    Explorer II
    Apr 23, 2020
    Assuming you're talking about the house batteries...yes, that's the isolator solenoid (or combiner if you prefer), and yes the coil is 12V.

    Note that, despite similar appearances, this is not a starter solenoid, but rather one rated for continuous operation. If it is faulty and you need to get a replacement, make sure it's similarly rated for continuous operation. Commonly it would be controlled primarily by the "run" circuit of the chassis, so it's active whenever the key is in the run position, similar to power for the vent fan or many other accessories. If you have an emergency start button or switch, there's a good chance it also activates this solenoid when pressed.

    The engine computer is not involved at all in enabling the charging of the house batteries.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Apr 23, 2020
    If the alternator is not charging the house batteries there is some kind of isolation device. often a solenoid not unlike the one in the photo or like a Ford Starter Solenoid.

    If it is not charging the CHASSIS batteries Well then the solenoid is NOT the problem.

    Most Motors (not all)

    Alternator--Fuseable link---Battery

    Now there may be any number of connnections between the Fuse link and the Battery and there may be more than one Fuse LInk.

    What is a Fusible link? Basically it's a long fusem a piece of wire designed to melt in the event of an overload like a regular fuse but a piece of wire Designed to melt without setting the thing on fire. Easily replaced.
  • enblethen's avatar
    enblethen
    Nomad
    Apr 22, 2020
    The relay in the photo may not be a starter relay. That could be the charge relay. 14 volts shows alternator voltage and the 12 volts is showing coach battery voltage.
    I would clean up the mounting bolts for relay as that is where it gets the ground to operate.
    Disconnect the small wire, use an Ohm meter to check for continuity to ground through the coil.
    Check for 12 volts DC on small wire when engine is running or when the auxiliary start button is pushed.
    Yes, you can apply 12 volts DC to small post to insure the relay works.

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