Dual Battery switch doesn't work

[The_Handier_Man1]

From: SupercubPilot  (Original Message)
Sent: 10/23/2003 10:21 AM

Just purchased with 40,000 miles

1979 Winnebago Itasca

Wt 12,300

Model according to place next to driver â€" ICF26RH

Vin 70F48K118095 CH. Vin CPS3793303884

454 Engine

1979 P-30 GM chassis (I think)

On the dash I have one of those dual battery switches that has three positions. The switch positions are Dual to the left, middle position, and mom to the right. I think that I know what these positions are supposed to do. I don’t think my system works and don’t have any sort of wiring dia. While the engine is running and alternator is putting out 14 or more volts. The main single bat is being charged and shows alternator voltage when I check it with the bat check switch and guage on the dash. When the battery switch is in the dual position to the left the alternator should be charging both the main vehicle battery and the set of dual motorhome batteries. It does not according to the voltmeter on the dash. While in the dual position with the alternator running I can check voltage on the single battery and that reads alternator voltage. When I check the dual motorhome batteries with the same rocker switch it only reads 12 volts. Shouldn’t it also be reading alternator voltage and be receiving a charge. The momentary switch position that is for connecting all bats together for starting does not seem to work either. I think that I hear a relay clicking once when I move the switch from the center position to the left. I can’t be sure.

What is most likely my problem? Where are the components located that control this transfer? How do I troubleshoot this? What do the components look like? Where can I get a wiring diagram? I just replaced my alternator. I replaced it with the same size unit that I took off which was 63 amps. Is this enough?

Please feel free to email me directly at hawkdc9@nospamnwcp.com (remove the nospam first).

Tim



From: Sea Hag
Sent: 10/25/2003 9:22 AM

I have a 76 D23C that I got in September  with a simalar problem I haven't had a chance to trace it down yet , the switch operates relays connecting the batteries together Dual for chargeing both while driving and MOM for Staring Assist. - See "General "on dicussion Board - "1977 manual" - There is info there on 1977-79 Winnebago / Itaska Service Manuals , I'm going to order one soon , ---- Sea Hag 



From: denison
Sent: 10/25/2003 9:43 AM

The dual-mom switch on my D22 only works sort-of. It will connect the batteries eventually, but seldom when I first switch to dual. It must take a good highway bump to help. I assume it is deteriorated wires between the switch and the solenoid, crud in the switch itself, a poor ground on the solenoid, or the aged solenoid. Ill eventually have to fix it, with a new solenoid, running new wires, including a good uncorroded ground wire for the solenoid, and maybe even a new switch with no cobwebs in its guts. I have never seen a wiring diagram for one of the winnebago coaches that was very informative. The dodge chassis wiring diagrams dont cover this circuit of course, as it was added by winnebago. You could probably guess what the circuit was about as well as what you could learn from the published diagrams Ihave seen. denison



From: Sea Hag
Sent: 10/27/2003 10:51 AM

The privious owners of my D23C have left quite a birds nest of wires under the dash and on the floor , alot has been changed . I'm slowly getting the colum and ignition wiring straitened out and back to the way it was intended to be , first things first . It's going to be a good winter project . Glad it has a working furnace  , ------ Sea Hag



From: melyash
Sent: 10/28/2003 12:15 AM

There are numerous postings on the Duel mom switch but basically the thing works like this.

The switch should be powered from the Ignition side of the key switch NOT directly from the battery. The the D/M switch allows you to charge both your coach batteries and your start battery in the dual position but that connection should only be made when the engine is running. That is the reason the switch (and solonoid it is connected to down by the battery). In the middle position the alternator on your engine just charges your start battery while the engine is running. The Mom position allows the coach batteries and the start batteries to be connected together in case you somehow ran your chassis (start) battery down. This allows them to provide like a jump start to allow you to start your vehicle off your coach batteries.

Usual problem is either corosion on the solonoid terminal, or between the solonoid and the vehicle chassis, (it uses the bolts it mounts with as a connection to ground) or finally the Solonoid, switch, wire or some combination might be bad. Try cleaning the contacts first. When you turn on the ignition but don't start the engine yet, flip the switch to dual, and listen for a click down at the solonoid. If you hear it, the solonoid is working and everything from the switch to it is ok. Now turn the ignition off, the unit should click again showing that the switch is wired to the ignition.

If the Dual Mom switch works with the key off, then it is miswired and can cause problems for you later. Also do not run the engine and the Generator, (or shore power) at the same time with the switch in Dual position, it can burn out or at least damage your alternator or Voltage Regulator.

There are a pletora of posts on these and other electrical related questions, just keep digging. Not every question has been answered, but Odds are better than even that the info your looking for is posted on these pages.

Email me if you have questions. So you have a supercub huh,  Never quite got the hang of taildraggers. Tricycle man myself. 635 hrs flying a PBY for a guy, A real character that one.

Matt



From: melyash
Sent: 10/28/2003 12:19 AM

Also, Harold Barre's book Managing 12 Volt Systems shows a diagram that pretty much sum's it all up on the circuit in question. It is a general diagram but it helps you understand what your looking at. Also Colyn Down Under (from this site) has written some books that are highly regarded. Have not read them but hear they are good as well.  Best of luck.

Matt