Intermittent ignition issue

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garyb1st

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Several times over the past week, I wasn't able to start the motorhome by inserting the key and turning it on. Thinking it might be the chassis battery (it's less than 3 months old) I used the switch that combines the house and chassis batteries. That worked so I went out and checked the chassis battery. It was fully charged at 12.5V.

After it was running I turned it off and it restarted normally. The next day, the same thing. Insert key and nothing. No lights. We always keep the salesman switches turned off and usually when I insert the ignition key it turns them on. This time that didn't happen. At least not the chassis side. However with key in ignition I pressed the combiner switch and the dash lit up and everything was fine. I wasn't attempting to start the engine with the switch pushed in. All I did was press the switch with the key in the ignition and everything lit up. The engine started fine. Then I turned the engine off and restarted it normally.

I'm thinking either the combiner switch or the BCC has an issue. A friend suggested the starter motor but that just doesn't make sense. It starts fine when the dash lights up and there is no hesitancy when starting it. The coach has a history on the BCC so maybe it's failing again.

Any ideas.
 
I had exactly this same problem this past late summer and early fall. It turned out to be a starter motor with a bad or flat spot. Got new one and problem was solved.
 
Did your dash fail to display lights too?
I can't remember, plus my dash lights are not very bright unless headlights are on, which they seldom are since I don't drive at night. All I know is that about 30% of the time, when I turned the key there was nothing but a small click. Guy had to climb under engine and hit something with a hammer and it started. At other times, it would start fine. They said there was a dead spot in the starter, whatever that means, and replacing it fixed it.

Also, I knew i had a 6 month old vehicle battery, so it was unlikely to be that. When it did start, it started just like normal.
 
Happened to me too.. The body builder replaced the battery connection terminals (Wire end) with standard crimp on ring terminals.. Steel or some metal OTHER THAN LEAD. the result was corrosion of the terminal and a poor connections.. A couple minutes with a wrench and a dremel wire brush and good as new.... When 9 years later I replaced the battery.. I re-did the wires to a single lead battery terminal ... No problems after that.
 
Thanks for the replies. A loose connection or bad ground sounds about right. I've had a similar situation with the power driver seat. From time to time, it will not move. The solution is to rock it back and forth.
 
Connections then if still a problem have the battery load tested.
3 months old sounds great but batteries can crap the bed at any age.
 
It turned out to be a starter motor with a bad or flat spot.
A starter needing a boost is often the early signs of it failing as it is a DC motor and when the windings begin to fail it will draw more current to run. Eventually the windings short to a point that no amount of current will cause them to work. But that wouldn't cause the dash lights to not come on.
A loose connection or bad ground sounds about right. I've had a similar situation with the power driver seat.
While that is possibly the cause, it could also be either the battery or something pulling power from the battery when the engine is not running. The battery will be at peak charge once the engine has been running but parked it begins to discharge. A good battery this happens very slowly but the rate will rise as the battery condition declines. Its also possible that the problem is the starter because not only is the battery condition at max after the engine runs but a warm engine take much less power to start. Battery voltage when idle tells us only part of the story as you need to monitor the voltage supplied by the battery when the starter is turning.
 
As I mentioned, this motorhome has had a history of Battery Control Center issues. Both the original owner and the second owner replaced either one of the BCC boards or the entire unit. Looking at the original owners records, he had the identical problem I'm experiencing. Could only start the motorhome by depressing the battery switch. That also explains why previous owners continuously replaced chassis batteries in the Pace. Not sure why the BCC would continuously fail but I'm wondering if I should just live with the problem or replace the board a third time. Sure would like to know why they're failing.
 
Put a voltmeter on the battery terminals, not the cables, and see what the voltage is when starting. If it falls below 10.5 volts, the battery is bad. The 12.5 volts may just be the static voltage with no load.
If you can get the MH into the parking lot, most auto parts stores can load test the battery.
If the house batteries are true deep cycle, they are not designed to be starting batteries. The high current needed to start can damage the batteries.
As said previoulsy, all connections should be checked also.
 
I'm thinking either the combiner switch or the BCC has an issue. A friend suggested the starter motor but that just doesn't make sense. It starts fine when the dash lights up and there is no hesitancy when starting it. The coach has a history on the BCC so maybe it's failing again.

First of all I am not an expert on your system but curious so I did a little googling. Not only is there the BCC but there seems to be an isolating solenoid that could be in play.

My curiosity is in that the automatic paralleling of the batteries does not appear to be happening but manually it does.

This thread I found seems very similar to your issue and has some good diagrams posted about the system.

 
Put a voltmeter on the battery terminals, not the cables, and see what the voltage is when starting. If it falls below 10.5 volts, the battery is bad. The 12.5 volts may just be the static voltage with no load.
If you can get the MH into the parking lot, most auto parts stores can load test the battery.
If the house batteries are true deep cycle, they are not designed to be starting batteries. The high current needed to start can damage the batteries.
As said previoulsy, all connections should be checked also.
Bought the battery at Walmart in September. The motorhome starts without hesitation after I depress the toggle switch. I don't have to keep the toggle switch depressed to start the engine so I don't believe it's relying on chassis batteries to help it start.

When I insert the ignition key and try to start the engine, nothing happens. After depressing the battery switch once the dash lights come on and it starts normally. However if I don't start the engine right away, after a half minute or so, the dash lights will turn off and I'm unable to start the engine. All I have to do is depress the switch again and the lights come back on. So depressing the switch makes the connection, but only temporarily. Seems it's either the switch or BCC.
 
My curiosity is in that the automatic paralleling of the batteries does not appear to be happening but manually it does.
Thanks for the link. I'll check that out.

When I use the switch, I don't believe paralleling is taking place. I've used the switch before but needed to keep it depressed while starting the engine. The way it is now, I don't need to do that. Depressing the switch is like turning on the chassis battery from the BCC.

As an aside, we have lithium house batteries. If I don't turn off both the house and chassis batteries at the BCC, the lithium batteries will continuously charge the chassis batteries at a rate of about 1.5 amps per hour and deplete the house batteries.
 
This is from link and likely the issue. "The isolator solenoid should energize when either of the batteries (coach or chassis) exceeds 13.2 volts. There is a 30 second delay before the solenoid energizes."

My lithium batteries maintain a voltage of close to 13.3 v until almost depleted. If the above comment is true and I don't turn off the batteries at the BCC, my lithium house batteries continuously charge the chassis battery.

The last time I had the motorhome serviced, about two weeks ago, they didn't turn off the batteries at the BCC. When I picked up the motorhome, the house batteries were down about 50%. That continuous charge may have overheated the solenoid.
 
Sounds like you are gathering clues.

One thing in my mind is whether you have disconnected from shore power when these faults are happening.

My second thought is what happens if you disconnect the House grounds leaving only the Chassis battery in the start equation.

It would appear to me that the Coach should start even if house voltage is seriously depleted or undetectable.

It's kind of like isolating systems so that faults can be exposed. It is possible to have weak Chassis grounds, bad chassis connections, a chassis voltage leak etc. that has been masked by having the back up of House batteries to help out.
 
Sounds like pressing the switch DOES parallel the house and chassis batteries for 30 seconds. Check your chassis battery - most likely it's completely or has a bad connection that's blocking current flow.
 

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