MOM Switch

pace89 · 12-17-2008, 12:59 PM

2004 Winnebago Sightseer 35 N.Had occassion to use it today(MOM switch), and it did not work. Engine battery was dead & coach batteries were 13.4 V. When cycling switch I could hear a clicking it sounded like it was coming from the stairway. Battery fluid levels were topped off 01 Dec. Only thing that I can think of that could have drained the Engine battery is the rear TV DC power switch was left on, but I thought that that switch is also powered by the coach batteries. Any one have any ideas ?? Both the Workhorse manual& coach owners manual do not say much about the switch except that there is one & how to use it.

pace89 · 12-17-2008, 12:59 PM

2004 Winnebago Sightseer 35 N.Had occassion to use it today(MOM switch), and it did not work. Engine battery was dead & coach batteries were 13.4 V. When cycling switch I could hear a clicking it sounded like it was coming from the stairway. Battery fluid levels were topped off 01 Dec. Only thing that I can think of that could have drained the Engine battery is the rear TV DC power switch was left on, but I thought that that switch is also powered by the coach batteries. Any one have any ideas ?? Both the Workhorse manual& coach owners manual do not say much about the switch except that there is one & how to use it.

skigramp · 12-17-2008, 03:57 PM

The purpose of the MOM switch is to hook your chassis battery and coach batteries in parallel.

The "test" is to look at the battery voltages while the MOM was depressed ... if they are the same (or within +/- .2) then the MOM is working

When you say it did not work ... what were your trying to do that you could not do?

Sometimes the chassis battery is so severely discharged that the batteries, even when hooked together in parallel with the MOM, will not have sufficient voltage to start your engine.

On my coach the steps are hooked to the chassis battery ... because of forgetfulleness on my part I left the ignition on for about a half day ... when I went to the coach and opened the door the steps did not deploy ... I was unable to start either my genset or engine, even using the MOM switch, until I had charged the coach batteries some.

pace89 · 12-17-2008, 04:39 PM

I was attemting to start the engine. That is when I found that the engine battery was dead. I have a battery voltage indicator plugged in the cigaret lighter that tells me what the coach batteries are, that is how I know that they were at 13.4 volts DC. I have used the MOM switch before to either start the generator when the coach batteries were low, and/or to start the engine when the engine battery was low. When I attemted to start the engine with the MOM switch this time the engine acted no diferently than it did when attempting to start with a low battery. The end result was to start the generator charge the engine battery with the generator then start the engine as normal. The voltage meter plugged into the cigarette lighter did not show any draw when trying to start the engine with the MOM switch.

ChasA · 12-17-2008, 05:16 PM

Pace89,
The problem is most likely the battery bridging solenoid is not making contact. This is a well known problem. The click you hear is the solenoid being energized. But the contacts inside the solenoid are not connecting. I have had some success getting the solenoid to work by holding the ignition key in the start position and toggling the MOM switch on and off (press, release, press, release...) several times. Sometimes it works, sometimes it doesn't. Search on this forum for "solenoid" to read about this widespread problem. This is the same solenoid that connects your coach batteries to the chassis batteries while the engine is running. If the solenoid is working right, you would see about 13.8-14.5 volts on the meter in your cig. lighter when the engine is running. If the meter reads only 13.5 or less, then the solenoid is failing.

pace89 · 12-17-2008, 05:53 PM

Do you know where that solenoid is generally located ?? I will just go ahead & replace it. I would like to thank everyone for their input.

Clay L · 12-18-2008, 04:54 AM

The solenoids are located behind the faceplate in a box in the upper left part of the propane storage bay.

There are a couple of thumb screws that allow you to remove the front cover of the box then four cross head screws that allow the faceplate to be removed.

The battery disconnect solenoid is on the left and the AUX solenoid is the one on the right as I recall. The wiring diagram can be obtained from the Winnebago web site.

I am familiar with the locations because my battery disconnect solenoid did not work when I first got the motor home. It turned out that when one the wires from the battery disconnect solenoid was crimped into a connector with one of the heavy gauge cables from the battery compartment, it wasn't stripped first. That was an interesting trouble shooting experience.

A couple of things confuse me though. Unless you rewired the lighter socket it is connected to the engine battery not the house battery. Also I don't think the generator charges the engine battery.
It really sounds like the house batteries were down. Note that as the other poster said you need to look at the battery voltage as the load is being applied to make sure it isn't dropping.

ChasA · 12-18-2008, 02:06 PM

Clay L.
All the 12V outlets in my MH are connected to the coach (house) batteries. You're right about the gennie, it only charges the coach batteries.

pace89 · 12-19-2008, 04:24 AM

Could I have some clarification about the gennie only charging the house batteries. The reason I ask that is because when I had the issue with my MOM switch I started the gennie and had the instrument cluster set to battery voltage and I observed a slow steady increase in engine battery voltage until I had enough to start the coach. Maybe the gennie does not directly charge the engine battery but it appears that somehow it contributes to increasing the voltage (converter?). Also when boon docking I use the cigarette lighter voltmeter to monitor coach battery condition, that is why I thought it is connected to the coach batteries??

I WILL CHECK LATER TO SEE IF THE CIGARET LIGHTER VOLTMETER DROPS WHEN STARTING THE ENGINE.
All the 12V outlets in my MH are connected to the coach (house) batteries. You're right about the gennie, it only charges the coach batteries.[/QUOTE]

Clay L · 12-19-2008, 05:54 AM

You guys are right, I was wrong about the cigarette lighter being connected to the engine battery. I just went over and checked mine and sure enough it read 13.68 volts which is the converter voltage.

I assumed it was from the engine battery because the wire goes over to the fuse panel behind the dash on the left and that is a Workhorse installed item.

When we get back from Lake Havasu later today, (buying Christmas groceries) I will take a look at the generator wiring diagram and see what I figure out about that.

pace89 · 12-19-2008, 07:10 AM

Iwas thinking more about the last post. When I had the issue with the MOM switch, and was able to charge the engine battery with the gennie the coach was on shore power so since I do not have a transfer switch you have to plug the service cord into the coach to power up the coach. So 1. I do not understand what caused the engine battery to get low if on shore power. 2. No transfer switch so if the gennie did charge the engine battery how ??

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by pace89:
Could I have some clarification about the gennie only charging the house batteries. The reason I ask that is because when I had the issue with my MOM switch I started the gennie and had the instrument cluster set to battery voltage and I observed a slow steady increase in engine battery voltage until I had enough to start the coach. Maybe the gennie does not directly charge the engine battery but it appears that somehow it contributes to increasing the voltage (converter?). Also when boon docking I use the cigarette lighter voltmeter to monitor coach battery condition, that is why I thought it is connected to the coach batteries??

I WILL CHECK LATER TO SEE IF THE CIGARET LIGHTER VOLTMETER DROPS WHEN STARTING THE ENGINE.
All the 12V outlets in my MH are connected to the coach (house) batteries. You're right about the gennie, it only charges the coach batteries. </div></BLOCKQUOTE>[/QUOTE]

Displaced Connecticut Yankee · 12-20-2008, 03:28 AM

I have a 2002 Minnie, and my momemtary switch connects the two batteries directly together if two conditions are met - the battery disconnect switch for the rear of the MH is "on" (12 volts applied to MH circuits), and I press the momentary switch. Once the engine is started, even if the rear disconnect switch is "off", the batteries are connected directly to each other by way of ignition voltage thru the normally-closed contacts of the momentary switch. This means that the alternator charges the house battery while driving, and if the generator is running, it is trying to charge both batteries in parallel with the alternator. I got all this from the Winnebago wiring diagrams. I have drawn myself a simplified diagram that I keep with my wiring diagrams.

pace89 · 12-20-2008, 04:52 AM

I feel confident that the generator does charge both batteries, my confusion lies with the fact that:
1. Coach was on shore power engine battery was low. It would seem that it would maintain a charge on shore power.
2. My coach does not have a transfer switch. So when gennie is running for the gennie to power the coach the service cord has to be removed from shore power & plugged in to the receptacle in the utility bay.
3. With gennie running engine battery was in fact charged while coach is on shore power.
???

Clay L · 12-20-2008, 07:49 AM

Regarding item number one, the converter does not charge the engine battery.
Some manufacturers do but Winnebago doesn't. In fact I have a BatteryMinder float charger connected to my engine battery that maintains the engine battery at full charge while I am connected to shore power.
The engine battery will discharge in about three weeks from parasitic loads if I don't have the Batteryminder connected.

With the service cord connected to shore power, there is no connection shown from the generator to the engine battery - at least none that I can find on the schematics.
There is a connection from the house batteries via the battery disconnect solenoid to the generator start solenoid but that won't charge the engine battery.

The wiring diagram is 04_d35n_wire_145364. Maybe you can spot something I am missing.

If I get a chance, later today I will start my generator, disconnect my BatteryMinder and see if the engine battery gets a charge in my rig.

Displaced Connecticut Yankee · 12-21-2008, 05:51 AM

In my Minnie, I have the Winnebago-supplied Parallax 7345 Converter. This converter does charge the batteries when an AC input is supplied, either from the generator or from the power cord.

Clay L · 12-21-2008, 06:23 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Displaced Connecticut Yankee:
In my Minnie, I have the Winnebago-supplied Parallax 7345 Converter. This converter does charge the batteries when an AC input is supplied, either from the generator or from the power cord. </div></BLOCKQUOTE>

Which batteries Karl?
House, engine or both?

With Winnebago class As only the house batteries are charged by the converter.

Clay L · 12-21-2008, 11:43 AM

Okay since it was time to check the water in the batteries anyway I took the step cover off and measured the Engine Battery Voltage :

Connected to shore power - generator not running:
Per Scangauge = 12.9
Per Instrument panel = 13.0
Per multimeter at battery = 12.78

Connected to shore power - generator running:
Per Scangauge = 12.8
Per instrument panel = 13.1
Per multimeter at battery = 12.77

So at least on my rig, running the generator while on shore power with the shore power plug not plugged into the generator socket does not charge the engine battery.

Just for grins I unplugged from shore power and plugged into the generator socket and started the generator. Got the same results as above.

There is only one solution Terry, you need to pack up, leave that cold MA winter behind and come on out here to AZ and park next to me so we can figure it all out.

Displaced Connecticut Yankee · 12-22-2008, 04:21 AM

Mine is a Class C, and I don't know how the Class A's are wired.

My wiring diagrams indicate that the converter charging output goes through my 12v Battery Disconnect relay (cuts house batteries on/off from the rv circuits) to the house batteries. If the engine is also running, the Battery Mode Solenoid (connects the house batteries in parallel with the vehicle battery when energized) closes, so the converter would be in parallel with the engine's alternator. If the engine is not running, holding the Momemtary switch would parallel the batteries, so the converter could (if electrically capable) charge all batteries at once.

This means that, if there is AC input (generator or shore power), the house batteries are charged. If, in addition, the engine is running, or the MOM switch is held down, all batteries are charged by the converter AND the alternator. I'm not sure that I like two simultaneous charging sources.

Tom N · 12-22-2008, 04:45 AM

From what I read on these forums Winnebago started to install a Trik-L-Charge on all class A's starting with the 2006 model run. With the Trik-L-Start all batteries are charged when connected to shore power or the generator is running. If this is incorrect someone please correct me.

-Tom

olly72 · 12-22-2008, 05:06 AM

I have a 2008 itasca sunrise 32h it did not come with a trix-l charger i had to install one. the winnebago people did say that some of the newer mode3ls did come with one just not mine oohhh well.