battery disconnect switch

[kartvines]

Installed a battery disconnect switch to eliminate the parasitic drain, and today when I finally got the batteries back installed after rewiring it all the engine started in both potions, so I now I am sure I connected it incorrectly I put it between the positive post and the battery isolator, should it installed be between the positive post of the started battery and the solenoid, I thought it looked like a starter solenoid but from everything I read it must be the boost starter solenoid, so can any one please provide me the proper installation of this battery disconnect switch?

[GaryKD]

Hi kartvines,
Consider installing the battery disconnect right on the battery post. If that is not possible, it needs to be installed before any parasite wires end up between the disconnect and the battery. Did you check your installation with a meter? If so, then somewhere between the disconnect switch and the battery there is a wire providing power to start the engine. Get the disconnect switch physically close to the battery.

[kartvines]

Yes I did test the battery disconnect switch before installing, it, and i must not have made my last post clear, the battery disconnect switch is attached to the positive side of the starter battery and the other end is connected to the battery isolator. The problem is there is still power to the starter, so it was not disconnected, unless I did not understand where it needed to be I had to assume it goes to the positive battery post to either the solenoid and or the isolator, so please help me out to correct the installation. On the positive battery post there was 2 battery cables one going to the solenoid and the other going to the isolator so it had to be one or the other, but before I rewired it again I wold prefer to understand that I did it correctly.

[Ray,IN]

I have my disconnect switch in the negative cable. There is only one usually, which makes this much simpler. FWIW, harbor freight sells a 200A keyed disconnect switch for about $6.

[kartvines]

I am using the heavy duty cut off switch I got from Harbor Freight, I installed as part of a fuse panel I installed to separate and fuse all of the wires going to the batteries to clean it all up, as you can see it this blog post:

1983 Fleetwood Pace Arrow Motorhome Restoration Project: Installation a battery disconnect switch and rewiring the batteries banks

[GaryKD]

Hi kartvines,
I've rewritten this post several times so I think what is in my brain got into the post in a way everyone can understand it. The easiest way to diagnose the problem may be to work with the cables on the batteries.

From the photos, I see a bunch of red wires. My assumption is you are 100% sure there is no power going through the disconnect switch when the switch is in the off position. Consider this as a next step.

The bottom line is to do one thing at a time and see if the engine will start. This is accomplished by removing a negative battery cable with the disconnect switch in the off position. Start with the engine battery (try to start the engine) and then the coach batteries (try to start the engine). If the engine starts with all the negative cables removed, there is a direct potential to chassis ground in the engine starting circuit. You will need to disconnect all the red wires from the starting battery. If the engine does not start, you know one of those red wires is carrying power to the starting circuit. If the engine does start the power is coming from the coach batteries.

If the engine does not start after removing the engine negative battery cable, a second disconnect switch on that battery post is a correct, easy and cheap fix.

I do not think you did anything wrong. I think the coach has some "interesting wiring". We need to sort through this and may need a second disconnect switch. If this is the case, nothing fancy just a disconnect switch that fastens to the correct battery post.

[wa8yxm]

IF the switch is properly installed then the ONLY wire hooked to the battery post goes to the switch... If there are 2 wires hooked to the battery post it's not fully disconnected.

As for "Between the battery post and _________" it don't matter so long as the only wire hooked to the battery post goes to the switch and it is also the only wire hooked to THAT SIDE of the switch.

Now, the difference between the disconnect solenoid and the starter solenoid.

House v/s chassis batteries.. you need two switches to disconnect both banks of batteries.. BUT CAUTION:
Some computer controlled engines will run rough following a disconnect.

[TQ60]

You stated the switch is between the battery and the isolator, and it still starts.

Well it SHOULD !!

The wire going to the isolator is ONLY for the charging of the batteries, the other side or center post of the isolator goes to the alternator, and the opposite end post goes to the other battery.

Be carefull as you may cause problems running your MH with some things not connected.

You should have a very large wire about the size of your pinky from the post going towards the engine, if not, more like the size of a pen, then you are working on the cabin battery and not the starting battery.

If you remove the large wire on the positive post the engine should not start and the lights inside the MH should work.

If this is not the case then return everything to normal or get another disconect switch.

THe disconnect switch should be very large and rated for at least 200 amps, 400 amps is better, it should state that it is for STARTING batteries.

The hardware for the wires should be 5/16 minimum bolts, 3/8 would be better. (bolt size not wrench size)

There should be only a single wire from the post to the switch, if the switch is mounted very near the battery then the wire is disconnected from the battery and connected to the switch, a jug may need to be added, most battery shops can do this for real cheap.

A new cable is then added from the switch to the battery post, same size as the one moved above, same battery shop can make one.

The best is a emergency vehicle switch, they are about 2 to 3 inches tall and about 6 inches in diameter.

They have 4 positions, OFF, 1, 2 BOTH, they are located reasonably close to the batteries, they are NOT cheap, but they can allow starting from either battery or both.

A good battery supply can provide all of the parts and hardware needed to install it yourself or do it for you.

[JimM68]

Oh boy...

Don't worry about the wire from the pos chassis battery to the starter. You hooked it up right the first time.

The switch IS disconnecting your chassis battery, and will prevent it from discharging.

Your engine still starts becuse it is being supplied power from the COACH batttery's!
Check your isolator box... That's where the problem is, and it is probably the cause of the draw too.

[kartvines]

I appreciate the feedback, so here is where I stand, the PO jerry rig much of the motorhome, but everything worked, so when it came to rewiring it I tried to put everything back to where it was beforehand, I do not have the experience to understand how to wired it myself and I know for a fact if I tried to wire it differently I would have surely screw it up.

So I can transfer the battery wire I now have connected to the isolator and switch it with the solenoid, I guess I will then see it that switches the power off, if not I guess I will leave it alone, not wanting to mess up everything, again it may not be wired correctly but before I started everything worked, and that is the outcome I need by the time I finish.

[JimM68]

If you connect your cutoff sw. to the starter wire...

Your engine won't crank with the disconnect off.

but everything in the coach will still have power, the dash, lighting, everything.
And you will still have your drain.

I'm assuming you want to make sure your battery (s) don't discharge so you don't get stranded?
Get a second diosconnect switch and put it on the house battery.
With both the chassis and the house batteries disconnected, you will not have any power draw.