Would removing the coach batteries affect engine starting?

dunecrazed · 12-28-2011, 06:25 PM

Someone told me i should post this here instead of where it was, here goes:

Link to original thread: Would removing the coach batteries affect engine starting?

When I turn the key I only get a click from the power distribution box. Tried jump starting, different battery, charged the heck out of the battery??? I am now thinking starter?? The coach batteries were shot so I took them out. Haven't tried to start the engine since. Could that somehow cause an inturruption in the electrical system? Always thought they were separate?

1994 Minnie Winnie with Ford 460...

Thanks for any ideas...

I got a few replies then I posted this:

Thanks! I will check to make sure there is no short there. I did get under there and jump the starter with a screw driver. Between the two large posts, the starter turned fine. When I jumped the large hot post to the small tab that has the little wire to it the starter engaged and turned. I turned the ignition on and did the same and the engine fired right up. Does this mean my solenoid is OK too?

I double checked the cliking sound and it IS NOT coming from the solenoid. It is coming from the power distribution box under the hood. Is there a secondary solenoid or relay in there that may have gone bad?

Thanks again guys...HELP!

GENECOP · 12-28-2011, 06:58 PM

These electrical systems can be complicated, chassis and house batteries are tied together in most cases...BOTTOM LINE, I think it is possible that your starting problems are connected....

Wanabee FTer · 12-28-2011, 07:07 PM

Is your RV equipped with a chassis/coach battery disconnect switch?
It sounds like the battery disconnect solenoid is either engaged (switch needs to be turned on) or stuck.
Use a 12 volt test light or DVOM to diagnose how far you are getting 12 volts through the starting system while key is on (cranking position)

dunecrazed · 12-28-2011, 07:07 PM

Guess I could put the old crappy batteries back in and see if that does the trick..?

dunecrazed · 12-28-2011, 07:17 PM

It does have a switch on the dash that you push in case your starting battery is dead that will allow the coach batteries to jump over and help crank the engine. It fell apart when I had to take all that apart to put a new stereo in. Maybe I have to put the batteries back in and hook up that switch????

Wanabee FTer · 12-28-2011, 07:24 PM

Quote:

Originally Posted by dunecrazed

It does have a switch on the dash that you push in case your starting battery is dead that will allow the coach batteries to jump over and help crank the engine. It fell apart when I had to take all that apart to put a new stereo in. Maybe I have to put the batteries back in and hook up that switch????

Bingo!
I think you just figured out what's wrong. The switch must be hooked up for the chassis battery to operate properly.

wa8yxm · 12-28-2011, 07:26 PM

Possibilities are many, however the house batteries have should have no effect on the coach batteries unless the engine is running.

Coaches can be divided into two primary groups.

Group one has a mono-direcitonal isolator system, running the engine does charge the house batteries (As well as the chassis) now depending on the isolator, if the house batteries are SHORTED, this can affect the engine battery.

The rest have bi-direcitonal isolators.. These work exactly like the above, PLUS, when you plug into shore power (Or run the generator) the house system can charge the chassis battery.

IN this case the comment about SHORTED, works both ways as well.

If the batteries are removed, (And the positive (Hot) wires properly protected to prevent shorting, then they are NOT shorted.

oh, the 3rd effect: When you press the Emergency start, aux-start or boost switch on the dash.. THe house batteries become the engine batteries. (That is they are "Jumped" to the engine batteries, yes, Motor homes come with built in jump starters)

subford · 12-29-2011, 05:41 AM

The batteries, starter, starter realy and the cranking system are OK.

Your problem is in the start circuit from the Ignition switch to the little wire at the starter relay where you put power on the small wire post. This switch stops you from cranking the engine if it is not in "P" or "N".

Also check the linkage to arm at the switch as if the cable is pull out of it bracket it will do this.

Check wiring under the unit going to the switch that is on the drivers side of the transmission. See if any of the wires have been eaten on by little critters.

If the wiring is OK it would be the switch on the side of the transmission or the Ignition switch itself. It could also be something bad inside the column not letting the Ignition switch go far enough to contact the "S" terminal. I am not talking about the key tumbler here but the rod or the switch itself.

The click from the power box is the PCM power & fuel relays.

dunecrazed · 12-29-2011, 03:13 PM

OK, put the coach batteries back in, reassembled that aux power swith on the dash and it's still the same.

Subford, I checked all the wires to that switch on the tranny and they looked fine. Not eaten or damaged. Could that switch just go bad for no reason? Any way to test it? It's all so strange cuz before I parked it for the winter, it worked fine. Only thing I did was take out the coach batteries. I am not good at all diagnosing electrical problems.

subford · 12-29-2011, 03:40 PM

Yes you can test the switch.

Here is how you can test it without a meter. Just jump the white wire with a pink stripe to the red wire with a light blue stripe. But make sure the RV is in park when you do this. You can remove the plug to jump the two wires.

The below image is for the 1994 class "C" RV.

GENECOP · 12-29-2011, 05:59 PM

Did you hook the batteries up correctly?

YC1 · 12-29-2011, 06:40 PM

"I double checked the cliking sound and it IS NOT coming from the solenoid. It is coming from the power distribution box under the hood. Is there a secondary solenoid or relay in there that may have gone bad?"

If this clicking sound is happening when you turn the key to start, have someone turn the key on and off and find the solenoid that is clicking. Take a picture or two of it and post here. The device should have two large wires and one or two small wires.

If you can't post a picture then measure the voltage on each of the large terminals before turning the key. Then turn the key and see what happens. Post that info. You may just have a loose wire on that solenoid.

You should not need the coach batteries. If they are out do be sure and insulate the battery positive lead that was left off or you could be in for a fire.