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Author Topic: Update Electrical problems  (Read 1041 times)
Confidently Ignorant
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« on: September 16, 2009, 11:26:14 AM »

To fellow newbies having some electrical issues.  After 3 weeks of being stuck I found that electrical issues are not what they seem.  Thanks to everybody who said don't do it yourself.  They were correct but I couldn't find people to show up at the bus.

Recap, I replaced the start batteries, hopped into the driver's seat turned the key and the engine turned over and started but would not run.  Sound like a run relay problem?  Newbie thought so.

On the first weekend I found I could start from the rear but not the front.  This led to a week of measuring ohms, volts and temperatures at every relay and circuit breaker I could find in the front of the bus.

I questioned my placement of the 12volt lead coming off the start batteries which led to experimenting by moving grounds and positives from battery 2 to battery 1, switching grounds to positives and positives to grounds, combining leads on one terminal, putting 24 volts to a 12 volt circuit etc.

These experiments led to not starting at all, headlights not working and the low air alarm staying on even when the key was out.

I learned that if an engine that normally starts and runs from the key or back panel; suddenly does nothing, no starter selonoid clicks, no sound anywhere it is probably the neutral switch on the transmission being out place.  It seems in one of my electrical experiments (24v reversed polarity?) I pushed the linkage away from its switch.   I have electric shifting not air. 

Jiggled the linkage and the engine started from the rear panel but still not the front.  Back to tracing out circuits. 

Found the front to rear switch panel in the engine compartment energizes the complete starting and running sequence.  As a safety feature when switched to the rear or off positions the bus cannot not be energized from the front even with a key. 

The switch was going bad and that is why the bus wouldn't start.  One of the poles quit operating so it would turn the starter but not provide a signal to keep running.  The switch is now wired so can be started with the key even when it is the rear position while waiting for another switch.  Napa no longer carries one. 

It was chance that the switch failed at the same time I changed batteries.  I changed the batteries  correctly but my newbie timidness led me to question my actions and caused more problems.

Lessons learned

1st, Take a picture before dismantling.  Good for confidence.

2nd, A 12 volt tap from a 24 volt battery bank involves taking a ground from the ground of the second battery and tapping the positive terminal of same battery.  There are apparently other ways to do it but this is loosenut (fool) proof.

3rd, Electricity is easier to troubleshoot from the source, batteries in this case, and trace to the problem rather than from the problem to source.  To many activities have more than one dependent actions.

4th, Circuit breakers are more helpful than fuses when tracing out circuit problems.  Circuit breakers will pop then reengage while you're working on a circuit all the while protecting.

5th, The board and chat are a big help.  I received some excellent advice and direction.

6th, Not all problems are related.  Shifter issues seemed to be electrical problems.  Switch was coincidental not related to the battery change.

Hope this helps.

On my way to the beach now.


Sold 85 Neoplan 33ft 6V92ta, sadly busless
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« Reply #1 on: September 16, 2009, 12:38:48 PM »

Mike, thanks for documenting your results!

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