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Topic: Motor battery not recharging 1991 Grand Villa (Read 913 times) previous topic - next topic

Motor battery not recharging 1991 Grand Villa

Hey guys I need some help, the battery for the engine is not recharging from the alternator.  The alternator is working but I have to use the boost switch to start the coach. What do I need to check. The battery is good I recharge it with a battery charger.  Thank you.

Re: Motor battery not recharging 1991 Grand Villa

Reply #1 –
Test voltage at the BATTERY ISOLATOR. 

Center lug comes from the alternator and should read mid to high 14's.

Two outer lugs are to the two battery banks and should read about .7 VDC lower than the center.

Let us know what you find.

Re: Motor battery not recharging 1991 Grand Villa

Reply #2 –
Photos below of typical early 90's OEM battery isolator (just in case you've never looked closely at it).  Yours could be different...

Note: On our coach (in the photo) the big 3/0 battery cables do not attach directly to the isolator.  Instead, they connect to the large studs on the BOOST solenoid.  From there, short red cables run up to the isolator battery posts.

Also, this battery isolator has 3 battery posts.  The main (start) battery is served by one post.  There are 2 posts for AUX batteries.  The two AUX battery posts are connected by a short jumper cable.  It is thought that this was done to allow 2 diodes to split the charging load going to the house (coach) batteries.

Re: Motor battery not recharging 1991 Grand Villa

Reply #3 –
 I don't see why you could'nt  use a direct cable to the engine battery to reduce load on the isolator .

Re: Motor battery not recharging 1991 Grand Villa

Reply #4 –
As always, every installation is different.  Our  91 GV is totaly different from what Chuck has posted.  We have a 3 post isolator which performs as Brett has described.  Our boost solenoid is located with the house batteries under the steps.  It always helps to make a wiring diagram of your set up for present and future use.  A signal tracer works well for doing this.  Have a great day  ----  Fritz

Re: Motor battery not recharging 1991 Grand Villa

Reply #5 –
Quote from: Protech Racing –
I don't see why you couldn't  use a direct cable to the engine battery to reduce load on the isolator .

There is a 0.7V voltage drop across the solid state rectifier.  If you connect all the batteries to the battery isolator, you can run a sense wire from the alternator's voltage regulator to the output from the isolator or directly to a battery and the alternator will compensate for the voltage drop.

Re: Motor battery not recharging 1991 Grand Villa

Reply #6 –
Quote from: Old Toolmaker –
There is a 0.7V voltage drop across the solid state rectifier.  If you connect all the batteries to the battery isolator, you can run a sense wire from the alternator's voltage regulator to the output from the isolator or directly to a battery and the alternator will compensate for the voltage drop.


Yes. Said another way, the alternator's sense wire should be connected anywhere in the battery side of the battery isolator to chassis battery bank.  So, at chassis battery lug of isolator, at chassis battery side of battery boost/connect solenoid or at chassis battery itself.  ALL should read exactly the same, since they are connected with large-gauge battery cable.

Re: Motor battery not recharging 1991 Grand Villa

Reply #7 –
Thank you for your help I have a bad isolator diodes are blown.

Re: Motor battery not recharging 1991 Grand Villa

Reply #8 –
Short term work around:

Move all wires to one lug.  You could drive anywhere like that.  Only negative is that all batteries will discharge while boondocking.

Several long-range solutions:
1. Replace with another diode-based isolator
2. Install a solenoid-based isolator with "trigger" being ignition
3. Simple marine ON-OFF switch with chassis battery and alternator to one lug and house battery to the other lug.

Re: Motor battery not recharging 1991 Grand Villa

Reply #10 –
While exchanging race cars at a client's  shop today. A late 90s P 30 based coach blocked the garage . Some basic electrical diog showed  that the engine starter battery cable to starter  amps are routed through the solonoid .  Some BA jumper cables and fully charged battery would get it running.
  I doubt that my Cat engine could start with the  starter cables  wired through a solonoid .  I will double check my circuits to verify that the battery is directly wired to the starter. I'm pretty sure it is. 

Re: Motor battery not recharging 1991 Grand Villa

Reply #11 –
Quote from: Protech Racing –
I doubt that my Cat engine could start with the  starter cables  wired through a solonoid .  I will double check my circuits to verify that the battery is directly wired to the starter. I'm pretty sure it is.
Mike,

Just to clarify, in the discussion above we have been talking about the charging battery cables going from the isolator to the battery banks, and the various ways that they can be connected or controlled.

We have not been talking about the starting battery cable that goes directly from the start battery bank to the starter.  On our coaches (with OEM configuration) the starting battery cable does not go through a solenoid (other than the one mounted directly on the starter motor).

Re: Motor battery not recharging 1991 Grand Villa

Reply #12 –
Wolfe10 gave me a good idea by using a continuous duty solenoid, I think that is the way I want to go.  Thanks for all you comments and help. Hope to see you on the road sometime.
Dennis

Re: Motor battery not recharging 1991 Grand Villa

Reply #13 –
Be sure it is a constant duty and rated at least as high as alternator output-- here bigger is better, as more surface area in contactors.

Wiring if replacing the diode-based battery isolator with a solenoid-based isolator.

Alternator and chassis battery to one large lug.

House battery to other large lug.

Ignition hot source to combine/close points in the solenoid.

Ground if not grounded through body of solenoid (i.e. presence of a second small terminal).  If no second terminal, body of solenoid must either be in contact with good clean metal on chassis OR run a wire from a hold-down of the solenoid to chassis ground.

 

Re: Motor battery not recharging 1991 Grand Villa

Reply #14 –
 I think that I will add another cable from the Alt to the start battery  if it is "currently" run through the  Solonoid.
 That will give me the house batteries  charged directly from the  #2 delco alternator and the #1 alt charging the start battery .

 The battery transfer switch is intact and OE, seems to work fine with 2 alt.