House batteries not charging when coach running

dougrainer wrote:

The 12 volts on the small wire to activate the charge solenoid does NOT come from the Alternator. It comes from an Ign side 12 volt fuse and wire. When you turn the ign OFF the solenoid opens. As to the post about junk Solenoids, I guess he does a LOT of RV repair and replaces solenoids. Me? I am a professional RV tech and yes, I replace a lot of solenoids, but on different RV's as the ones we install and get from regular RV suppliers rarely fail. There are 2 types---100 amp (your type) and 200 amp (called a big boy). Most Diesels built in the past 15 years use the 200 amp model and older Diesels and Gas rigs use the 100 amp type model. Doug

Doug, thanks for the info. Here is what I find odd with what you are saying. The signal wire on my charging solenoid is only receiving 7V. As far as it coming from a keyed ignition, I don't know about that either. When I tested voltage at the back of the alternator I had 1 small wire receiving 12V and another with 7V (same as signal). I took the 7V wire of the alternator and put it onto the lug that was supplying the 12V small wire and then had 12V at the signal wire for the solenoid. So I'm assuming the solenoid is getting it's signal from the alternator once the engine is running?? ?? Heck, I don't know. I'm not trying to dispute anything your are saying, i really appreciate your help! I purchased my coach in 08 and it has been an electrical nightmare from day 1. Ever have your headlights shut off on you in the middle of the night? I have......multiple times. I called tiffin on it and they sent me a new head light switch for $60. Not bad I thought. What they failed to tell me is that I also have to purchase a $450 wiring harness to adapt it to my wiring. Haven't been able to pull the trigger on that one yet. I just wired a few relays in and it has helped. The way my coach is wired (and I guess I assume everyone else's), my lights run off of the house batteries. So when the house batteries go bad......your ship outta luck! I guess I'll run it like it is.....

luckydog3550 wrote:
I went out and purchased one of them GARBAGE continuous duty solenoids from Napa, installed it and everything is charging as it should be. MEXICO: I am curious to know how jumping the 2 sets of batteries together could be life threatening as you state? Even if I forget to disconnect them whats the worse that could happen besides running both sets of batteries dead? Thanks for the information.

The 12 volts on the small wire to activate the charge solenoid does NOT come from the Alternator. It comes from an Ign side 12 volt fuse and wire. When you turn the ign OFF the solenoid opens. As to the post about junk Solenoids, I guess he does a LOT of RV repair and replaces solenoids. Me? I am a professional RV tech and yes, I replace a lot of solenoids, but on different RV's as the ones we install and get from regular RV suppliers rarely fail. There are 2 types---100 amp (your type) and 200 amp (called a big boy). Most Diesels built in the past 15 years use the 200 amp model and older Diesels and Gas rigs use the 100 amp type model. Doug

I went out and purchased one of them GARBAGE continuous duty solenoids from Napa, installed it and everything is charging as it should be. MEXICO: I am curious to know how jumping the 2 sets of batteries together could be life threatening as you state? Even if I forget to disconnect them whats the worse that could happen besides running both sets of batteries dead? Thanks for the information.

luckydog3550 wrote:
Will any 3 post solenoid work?

NO!

There are INTERMITTENT DUTY solenoids

Then there are CONTINUOUS DUTY solenoids

Many cannot be told apart by looking at them. An intermittent duty solenoid that is incorrectly used for "continuous" duty WILL BURN OUT in short order.

It gets worse: About eight out of ten of those metal can "continuous duty" solenoids I autopsy turn out to be GARBAGE. Insufficient copper contact area, magnet coil windings that FAIL to have enough turns with big enough copper to have great magnetism (contact strength)*. A one ply tire with a ten ton load. How does one "pick out" the good ones from the garbage when they all look the same? After paying TWENTY FIVE DOLLARS for a supposed "top-of-the-line" brand solenoid, having it fail, taking it apart and finding it to be the same level of garbage as the ten dollar solenoids I am convinced only an ESSEX TOWER TYPE SOLENOID is with the bother.

*You can wind a magnet with FEWER turns of SMALLER gauge wire and end up with EXACTLY the same ohms resistance and two-thirds the magnetic pull. How ya gonna tell? Huh?

I have given up playing guessing games with solenoids used for battery splitting. Even the Cole Hersey brand now is garbage. A good ESSEX tower type solenoid is ten times the product.

When you run a WIRE to a switch, all kinds of things happen. You forget to throw the switch, the wire breaks, the terminals break, the switch itself goes bad. How many dozens of feet long is that EXPOSED switch control wire? This type of technology rates right up there with a tube-type adding machine.

A SELF-CONTAINED smart solenoid is the way to go. Remember something that may save your life and not being forced to remember throwing the switch. Use that memory slot for the better half's birthday or your anniversary.

A "smart" bi-directional" smart switch is the way to go. When ANYTHING charges ALL BATTERIES CHARGE, automatically. And only short wires are needed. Even a 15-year old can install one. They are SIMPLER to install than a regular GARBAGE solenoid.

I like the 200-amp model as they will go many years and NOT BURN OUT. I am a cheapskate but I am not stupidly cheap. One of these smart solenoids is the best money I've ever spent.

wolfe10 wrote:
Two issues:

As you said, one large lug is connected to the chassis battery and reads correct chassis battery voltage (14 with engine running).

Problem #1 is that the other large lug which connects to the house battery should read that battery's voltage-- probably in the 12.5 VDC range, even with engine off.

Problem #2 is 7 VDC to the signal wire. You can use a small gauge wire (it will carry less than one amp) from chassis battery large lug to signal terminal (remove the signal wire first, so you don't back-feed that circuit). Now the two large lugs should read the same voltage, as they are joined through the solenoid.

Most Ford solenoids are intermittent duty-- you will need a CONSTANT DUTY SOLENOID of sufficient rating (amps).

Thanks again. Problem 1 is not a problem. I removed the house battery cable and am reading voltage directly off the solenoid. Now, I'm not sure problem 2 is a problem either. I removed the isolator solenoid from my generator compartment and tried to. I finally got some voltage to the bottom lug, however it was only 6V. Then (DUH), I grounded the solenoid and whammo.....14V at the bottom lug. Apparently the ford solenoid will not work at all, or is faulty as i tried it again with ground and still didn't work.

So, having said all that, did I find my problem? It seems now, that having 7V to the signal post is not a problem?? ?? While I had the ford solenoid on, I took the signal wire off the alternator and gave it 12V and the solenoid still did nothing. Here's to hoping I found the problem. Thanks again for all the help!

If all else fails, just replace the chass/house battery solenoid w/ a 3 pole continuous duty, then run a 14-16 ga wire from the small term on solenoid to the accessory (hot when on) side of the ignition switch, that's all there is to it.

Yes, the proper way to do this as a temporary measure is NOT to use a jumper cable, as both ends are hot and supplied by a large battery bank, and if one end jumped off and touched any metal on the coach, you are looking at an instant WELDING MACHINE and likely fire.

The proper way is to mark and remove a wire from one large lug and add it to the other large lug. Return to original position to disconnect. If you are going to be on shore power the whole weekend (when not on the road) no issue with leaving them in the "both on one lug" position-- your charger will automatically charge both banks.

Dog,
you are right on,......just connect the positive of the house and chassis batteries together, and disconnect when parked. That will NOT hurt anything, and is exactly what the solenoid is suppose to be doing when it (the small terminal) is activated (energized) by the ignition switch

Two issues:

As you said, one large lug is connected to the chassis battery and reads correct chassis battery voltage (14 with engine running).

Problem #1 is that the other large lug which connects to the house battery should read that battery's voltage-- probably in the 12.5 VDC range, even with engine off.

Problem #2 is 7 VDC to the signal wire. You can use a small gauge wire (it will carry less than one amp) from chassis battery large lug to signal terminal (remove the signal wire first, so you don't back-feed that circuit). Now the two large lugs should read the same voltage, as they are joined through the solenoid.

Most Ford solenoids are intermittent duty-- you will need a CONSTANT DUTY SOLENOID of sufficient rating (amps).

wolfe10 wrote:


Not sure I understand how the signal terminal connected to the house battery (sounds like an odd signal source to me-- I would have expected it to be an "ignition hot" source and usually off the chassis battery) could have 14 VDC and yet the large lug to the house battery could have 12.5 VDC.

If neither large lug is receiving alternator output (14 VDC)with the engine at high idle, the problem may be in your alternator or between the alternator and solenoid.

I think the signal terminal is getting power from the alternator. The top lug is getting power from the house batteries, which are not being charged, and the lower lug runs the dash lights etc, like you stated