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rgreen45 · 12-10-2016, 06:23 AM

Hi gang ... I'm working on a 2011 Allegro Red and the owner says the house batteries aren't charging while driving. In the right rear compartment, behind a plexiglass plate, is a charge solenoid. It has to large posts (one chassis batt and one house) and 2 small posts.

One of the small posts has DC+ voltage. It also includes a wire that loops over to the other small post which I believe contains a diode as there isn't DC+ voltage on the other post.

Anyway, with engine running and I momentarily remove the DC+ voltage from the small post, then reconnect it, the solenoid clicks and begins charging the house batteries. After about 30-60 seconds however, the charge stops but I don't hear the solenoid disengage nor does the DC+ voltage on the small post go away.

The solenoid isn't getting hot and my suspicions are this. Either the solenoid is breaking down and losing contact or there's a smart board somewhere that doesn't allow house battery charge until the voltage drops to a specific level.

Also, that diode wire baffles me. I can always call Tiffin on Monday but I'll likely spend most of the day on hold.

TIA gang for and advice.

APhotoWizard · 12-10-2016, 08:54 AM

I have a 2001 Alegro bus and had the same problem. The system works like this:

One of the two small posts is connected to ground. The other of the two small posts is connected to a special wire from the alternator that produces voltage only when the engine is running. The two large posts are each connected to one of the two battery banks.

When the engine starts, the alternator provides a nominal 12 volts to one on the small posts and the since the other is grounded the solenoid closes and connects the two battery banks together.

Problems. There is some indication from the solenoid manufacturer that this solenoid should only be mounted vertical and Tiffin mounted my horizontal. This makes the solenoid have problems when it gets older. I remounted mine vertically and things got better.

On the other hand this did not fix the problem. What fixed the problem is a new alternator and replacing the wire between the alternator and the solenoid that had chaffed against the frame and shorted.

My suggestion. Meter the voltage at the post with voltage. With the engine running there should be 12 volts (Approximately) at one post and its should stay there until the engine stops.

If the voltage is OK change the solenoid. Note: My solenoid was repairable by grinding the rivets off and replacing them with screws. Since the unit was worn from sideways mounting I eventually replaced it anyway.

If the voltage is nonexistent or drops, follow the wire and check the voltage at the alternator end. If the voltage there is ok then replace the shorted/broken wire. If the voltage drops, replace the alternator.

Note: the alternator output may change from 13-15 volts as the engine speed is increased, but it should not drop below 13 at any point. Voltage drops as the engine speed increases is another symptom of a bad alternator.

My unit does not have a diode across the terminals, but that is not an unusual way to keep the inductive kick from the solenoid coil from getting back into the electrical system. It is not likely a problem.

I hope this helps. Let me know if I can help further.

select55 · 12-10-2016, 09:55 AM

Quote:

One of the small posts has DC+ voltage. It also includes a wire that loops over to the other small post which I believe contains a diode as there isn't DC+ voltage on the other post.

whats with the wire that loops over from the 12V supply source?
and why the diode

Kiawah · 12-10-2016, 10:30 AM

When a magnetic coil / inductive loads are energized, they will want to stay energized. If/when you remove power, the magnetic field will create a spike in voltage on the primary. The diode is a way of burning off that voltage, so it doesn't backfeed a high voltage spike on the line that comes from the alternator.

On some relays, the spike in voltage can actually turn the relay back on. I have some home automation controllers (which controls a ballasted light), which can turn itself back on after the computer program turns it off. Incandescent (resistor element) loads don't have this problem.

select55 · 12-10-2016, 10:34 AM

Quote:

Originally Posted by Kiawah

When a magnetic coil is energized, it will want to stay energized. If/when you remove power, the magnetic field will create a spike in voltage on the primary. The diode is a way of burning off that voltage, so it doesn't backfeed on the line that comes from the alternator.

thanks I kind knew what the diode does (u confirmed) what really confuses me is what this jumper wire is all about?

Kiawah · 12-10-2016, 10:45 AM

Speaking generically about relays (not necessarily your device), relays can fail for a couple different reasons.
- The primary wire, which is the wire that wraps around the coil and 'energizes' the relay burns up, and fails to then energize the relay. You hear yours latch, so this isn't your problem.
- When the relay latches, it physically moves contact points. Sometimes the physical movement piece binds. Since you hear your's latch, this most likely isn't your problem (assuming it moves perpendicularly correctly).
- When the secondary contact points touch, they get pitted and burn from the switching currents. They either fail to make contact, or do so with a high resistance that then limits the current. Since this relay can be switching hundreds of amps of current, this would be the failure I would expect to see.

Same type of problem I would expect to see when people have transfer switch problems. They fail to turn off high current devices before switching their power source, and that current causes the contact points to arc and burn. Over time, the contact points will fail to make good connections, and eventually the voltage won't make it thru to the breaker box. The fix, replace the relays (if one could find the replacement parts and take it all apart), or replace the whole transfer switch (easiest).

rgreen45 · 12-20-2016, 06:33 AM

Thank you for the input folks!

Veloce007 · 01-04-2019, 02:10 PM

Rv dealer has advised me the tiffin charge solenoid is defective, wanted 650$ to replace, I purchased a new white Rogers solenoid and want to replace. I see 12 v on both the large red leads, opening both the chassis and coach battery disconnects and removing shore power did not remove the voltage. Is it safe to remove the leads to transfer to new solenoid with voltage present?

I am not having any slide issues on my 2007 Allegro Bus QRP

twinboat · 01-04-2019, 02:25 PM

Remove the negetive battery terminals of both house and chassis batteries.

The cables in question are before the disconnects, so they will be hot until the cables are off the batteries.

Also pull the plug on the shire power and shut down any solar, if equipped.

Veloce007 · 01-04-2019, 05:33 PM

Thank you, I checked the wiring diagram but there is not much detail , only a line indicating both house and chassis on opposites of the solenoid which is supposed to be N.O. I could not find how the solar charger connects (pretty poor diagrams) I did neglect to cover the solar panel .
I am surprised the isolators do not completely isolate the battery banks from all connections and possible drains.
It is a bit difficult to access the front 4 house batteries (8 in total) , the chassis batteries a little easier to access.

twinboat · 01-04-2019, 06:54 PM

Quote:

Originally Posted by Veloce007

Thank you, I checked the wiring diagram but there is not much detail , only a line indicating both house and chassis on opposites of the solenoid which is supposed to be N.O. I could not find how the solar charger connects (pretty poor diagrams) I did neglect to cover the solar panel .
I am surprised the isolators do not completely isolate the battery banks from all connections and possible drains.
It is a bit difficult to access the front 4 house batteries (8 in total) , the chassis batteries a little easier to access.

The isolators function is to isolate one battery bank from the other. That way as you draw down the house batteries the chassis batteries are left fully charged.

It closes when a charging source is detected to charge both battery banks.

The disconnect solenoids disconnect the batteries from the RV, although there is always some things not run thru them.