Battery combiner relay or solonoid not working properly.

[funjnt]

Ok so I have replaced my battery combiner solonoid as it wasn't working properly. As in it wasn't closing and allowing the house batteries to charge while the motor is running. This is the problem now..

I have tested the relay with my power probe. When the coach is off I can apply ground to the small connection at the bottom and the solonoid will click and close properly. When I push the emergency start button on the dash it will click and close properly. So the solonoid is functioning properly in this fashion.

Now, when I start the motor, the solonoid should close automaticly as it always has to charge house batteries and it doesn't close. When I apply a ground to the small terminal at the bottom with motor running, the solonoid doesn't close. When I push the emergency start button the solonoide doesn't close. This is baffling to me. It doesn't make sense. I have also replaced the oil pressure switch on the motor a few years ago as it was leaking and not allowing the solonoid to close when running. There are three wires on this solonoid, did something fail or cross?

The only think I can think of is that there is something injecting 12v into this circuit thus preventing the ground from triggering the solonoid? I haven't tested the wires individually but what else would stop the grounding of this terminal and not allowing the solonoid to close with motor running?

Does anyone have any experience with this situation?

[TacomaJoe]

No experience with your situation exactly but I know how relays work. When you apply the ground and pull in the relay there must be +12V on the other side of the relay coil. When you start the engine it would seem to me that the +12V is being removed for some reason. I'll guess that some control board is looking at the inputs to determine if it should enable that relay.

Try a meter/test light on the other coil terminal of the relay.

[funjnt]

Ah that makes sense. As I said there is 12v on the other small terminal when sitting turned off. That is the first thing I did and when I apply ground to other terminal it clicks pulling in.

I haven't checked the voltage with it running. There are two diodes supplying voltage from each leg as in the chassis batteries and the house batteries. I will check these. I will also check if anything is back feeding the other circuit.

Now that I think about it. I have had another electrical problem. My step computer shorted out backfeeding the run circuit of the key switch. In other words the step wouldn't stay out even when turned off. I went to the coach and could hear the anti lock brake relays cycling as if the key was on. Started the coach and it wouldn't turn off. I smelled the relay box for step under neath the step getting hot, only reason I found this one as the smell. So it is unplugged till I order new box. Not sure if this has any relation but will check this out.

[gpounder]

I agree something is drawing the + power away from the solenoid when the ignition is on. BTW you should have 2 wires on the negative side. One goes to the boost switch up front and ground when pressed. The other to the oil pressure sender also ground when pressure is up. I found a bad crimp connecter on the oil wire that cause it not to work for me.

[a250gpguy]

Another thing to take a look at could be the 200amp breaker in the battery compartment.

Ours went bad and the battery boost switch would not work until after we replaced..though we did have low batteries too.

Ch

[funjnt]

Good points again. I will check the two wires and yes, one is the boos switch and one is the pil pressure switch. I will look here maybe. I did replace the oil pressure switch a few years ago. Maybe a wire came off? The boost switch works when it is turned off as I can hear it cycle with power probe on the lead when I press button. Would it have anything to do with the two diodes?

[TR4]

WOW, this is unusual. It’s a pretty simple design. The solenoid works by applying power to the solenoid coil (small terminals). The positive side of the coil is always energized, getting power from the large terminals. The large terminals are connected to the battery. Chassis battery to one terminal, house battery to the other.

They’ve installed two diodes. One from the large chassis terminal to the positive (small terminal) side of the solenoid. The other is installed from the large house terminal to the positive (small terminal) side of the solenoid.

I believe the diodes are used to supply power to the solenoid coil from either the house or chassis batteries without back feeding one side to the other (the coil can get power if one battery is low).

So, the large terminals should always have power, since they’re connected to the batteries. The coil should always have power, unless both diodes are bad. The solenoid is controlled by a ground signal to the solenoid.

This is what I would do. Take a voltmeter and connect it to the positive small terminal of the solenoid and a good ground.
Do you have 12 volts?

Now stay connected and start the engine.
Do you have 12 volts?

Bill

[funjnt]

Hey Bill very good discription. You are correct with all of your descriptions. Everything is connected as you say diodes to the big wires and all.

So, I haven't checked for power to the small terminal when rig is running yet but I have assumed there is power as the batteries are connected. And yes each diode is in place, one from the house and one from the shassis so you can always toggle the solonoid.

I am going to check the positive terminals to see if positive when running and I am going to check the two negative wires to see of something is injecting current thus blocking the ground. Looks rainy today but this weekend. I will keep updating here as I am perplexed on this simple thing.

[p1havasu]

Hey guys, may I jump in on this as I may have the same exact problem. 2004 CC Inspire (love this coach).

Chassis battery not charging the house battery with engine running. Important on the road since I have an LG house fridge running on the inverter while driving (which is not charging). Also have a digital echo charger, which seems to me wired to charge house to chassis, backwards from the need. Recently a shop said they fixed the ground connection from the oil pressure sending unit and all good. Not the case.

Trying to understand the system, I do think simple and gaining ground. I don't think a problem with battery boost (not positive). So far, am thinking a bad diode from the chassis side since the small terminal always tracks the house battery voltage. Or that expensive solenoid is bad, which I hope not. If this is working properly, something else is not telling to charge the house.

Do have voltage checks to convey, Vary for house vs chassis, and there is always the same voltage at both small terminals. The other solenoid for the house seems to be working fine, I think.

Other buddies with the same fridge maintain charge fine from the alternator while on the road.

Thanks for any help. Bill, you may solve both our problems here. Much appreciated.

[gpounder]

Originally Posted by funjnt

Ok so I have replaced my battery combiner solonoid as it wasn't working properly. As in it wasn't closing and allowing the house batteries to charge while the motor is running. This is the problem now..

I have tested the relay with my power probe. When the coach is off I can apply ground to the small connection at the bottom and the solonoid will click and close properly. When I push the emergency start button on the dash it will click and close properly. So the solonoid is functioning properly in this fashion.

Now, when I start the motor, the solonoid should close automaticly as it always has to charge house batteries and it doesn't close. When I apply a ground to the small terminal at the bottom with motor running, the solonoid doesn't close. When I push the emergency start button the solonoide doesn't close. This is baffling to me. It doesn't make sense. I have also replaced the oil pressure switch on the motor a few years ago as it was leaking and not allowing the solonoid to close when running. There are three wires on this solonoid, did something fail or cross?

The only think I can think of is that there is something injecting 12v into this circuit thus preventing the ground from triggering the solonoid? I haven't tested the wires individually but what else would stop the grounding of this terminal and not allowing the solonoid to close with motor running?

Does anyone have any experience with this situation?

Dude this circuit is real simple. If there is a diode it is there for spike protection and it can be removed for testing. When the solenoid is not on you will get the same 12volts from each of the small terminals to ground. Remove both wires from the small terminals. One will have 12 volts, the other no voltage and no continuity to ground. The one that has no voltage is the grounding wire. It goes to the boost switch and when the switch is pressed will ground. That same wire also goes to the oil pressure sensor. (My rig this wire is actually two wires). You can test the ground part with a continuity tester/voltmeter to see the boost and oil switches working. Now the relay. Easy to test. Put + and - to the small terminals and here is click. When active the 12+ power on the large lugs will be the same. If not then the contacts inside are bad. One more thing you can do before you do anything is check the boost circuit. Run the engine and wedge something under the boost switch to keep it on and then check your batteries at the large lug on the solenoid, if the the same voltage the the relay is good, now look at the oil pressure side.

[TR4]

Simple way to look at the solenoid.
It has two large terminals. One going to positive side of the house batteries. The other going to the positive side of the chassis battery. So you basically have two separate batteries meeting at the solenoid. You want these separate when you’re dry camping so you don’t run down the chassis battery.

But, when you’re driving, you want to charge your house batteries with your alternator. So you want to join those two large terminals on the solenoid.

To do this you need to apply 12 volts to the small terminals, one side being positive and the other terminal being negative. Since you have 12 volts positive on both large terminals you don’t have to go far to get the positive voltage.

So what side do you take the 12 volts from, the house side or the chassis side? If you’re taking it from house side and the house batteries are low, the solenoid won’t work. Same goes true if you take the power from the chassis side, chassis battery low, solenoid doesn’t have enough power to work, no boost.

I believe this is why they take power from both large terminals to power the positive side of the small terminal (power from chassis and house batteries). But, so you don’t back feed power from house to chassis they use diodes (this keeps the batteries isolated).

So the solenoid always has the positive side of the small terminal powered . It just needs the negative connection from the boost switch or oil pressure sending unit.

This is how I would check the solenoid.
You should have 12 volts positive on both large terminals.
You should have 12 volts positive on one small terminal (the one with the diodes connected)
Now disconnect the positive battery cable from the chassis battery.
Check for voltage between the disconnected cable and ground, should be zero.
Now ground the other small terminal on the solenoid,you should have 12 volts on the disconnected chassis cable.

If this doesn’t make sense, PM me.

Bill

[p1havasu]

OK, thanks for the inputs. Now smarter than yesterday and figured some things out.

The diodes are absolutely good. I removed both of them and checked them.
Both batteries feed the small positive terminal as they should and no current flow backwards.

The solenoid also looks good. The small ground terminal shows same voltage as the positive side at about 13V. But the boost switch grounds it and the solenoid actuates. Manually grounding that terminal also actuates the solenoid, so must be good. When grounded, both chassis and house batteries read the same at about 13V. When engine running, and only when manually grounding the terminal, have 14 volts to both batteries. So the system must work.

The above is know for sure at least.

Still have problem feeding alternator to the house while running. Have two wires on the ground side of the small terminals and reads about 13V. The black wire comes from the boost switch. The blue wire must go to or form the oil pressure sender, but cannot confirm in wire list. Each one connected by itself also shows the same 13V and neither are zero if I did that right.

As mentioned prior, a shop found the oil press sender had grounding problem, fixed it, and now all good. Is that still the problem to revisit and dig deeper or perhaps could be something else here? Perhaps the boost circuit.

Thanks, Mike

[TR4]

Mike, try this. Disconnect the house batteries. Now check for check for voltage on the two large terminals. One should have 12 volts, the other no voltage (since you’ve disconnected the house batteries).
Now ground the small terminal (the one hooked up to the boost switch and oil pressure sending unit).
You will hear a click and now read 12 volts on both large terminals. This is power being sent over from the chassis battery.
The alternator will now be charging both batteries.

Note; in my prior post I stated only one of the small terminals will have 12 volts, this was incorrect, they both should have 12 volts as Mike stated. The small terminals are part of the coil in the solenoid.

Bill

[HarryStone]

The schematic above doesn't show the input from the BCC. The power doesn't come directly from the house, or starter battery. It comes from the BCC, and there is a circuit there to deactivate the circuit until the primary battery is charged (start) and then the voltage of the primary battery activates the circuit to allow the solenoid to close (applies 12VDC) and then it charges the house batteries.