Not gen light is on, a/c and heat wont work

[ilyafish]

We are out on tour, will be home in 3 days and i am rewiring my bus completely.  I have a ton of electrical problems and am absolutely tired of dealing with them.  Here is the latest issue:

About 10 minutes before we got to the show, one of the batteries died.  This battery is the one that is hooked up to the 12v veggie system (i dont have a vanner equalizer either) so i am assuming that the veggie system killed the battery.  At this time, the not gen light popped up on my dash.

After the show, we charged up the dead battery, and limped our way to a walmart supercenter with barely any power for headlights or running lights or anything.  Got there, got a new set of batteries (i have 2 12 volt car batteries and one 8D).  Replaced the batteries.  Went back to full power on the bus, however the not gen light is still on, even when driving and fully aired up.  Also the OTR air and heat wont work now.  I called MCI, and he said that it sounds like an alternator issue.  My batteries are getting a full charge, and i did some research on the board and it sounds like the alternator is fine, i just have something else going wrong.  The only reason i am posting this topic which has been brought up before is because it sounds like it coincides with the OTR air system.  Any help and advice would be great.

Thanks!

[Sean]

The OTR air system is interlocked to the alternator "relay" terminal, which also controls the "Not Gen" light.  So long as that light is on, you will not be able to run the air.

The alternator has a "Relay" or "R" terminal, which puts out roughly half of the alternator's rated voltage when the alternator is producing power.  If you have a 24-volt coach, this terminal will produce about 12 volts when the alternator is working.

If the Not Gen light is on, either the alternator is not actually producing any output, or the Relay circuit has a problem.  The diagnostic procedure varies greatly depending on which of those two it is.

If you can get to the alternator, fire up the bus and measure voltage:

- Between ground and the Alternator positive terminal.
- Between ground and the Relay or "R" terminal
- Between ground and the F, F1, and/or F2 terminals.

I advise you to remove your jewelry before fiddling with the alternator, and be careful not to short anything.

If you read ~27 volts or better at the + terminal, and ~12 volts or better at the Relay terminal, the problem is in the Relay/Not Gen circuit.  If you read ~24 volts at the + terminal and 0-4 volts at the Relay terminal, the alternator is not charging, and we can start looking at the regulator (the other measurements will be handy then).

-Sean
http://ourodyssey.blogspot.com

[ilyafish]

where is the relay exactly located?

thanks!

[Sean]

Measure the voltage directly at the alternator, on the terminal marked "Relay" or "R."

I'll let someone more familiar with MCI layout answer the question about where the HVAC relays are located, since I am not an MCI guy myself (but I know the 50DN alternator quite well).  I would assume they are in the panel below the driver window, but that's just a guess.

That said, you really want to start at the alternator -- if you check at the relay and there is no voltage, you'll still need to go back to check it at the alternator anyway.

-Sean
http://ourodyssey.blogspot.com

[gus]

Sean has shown you the way toward solving your problem.

However, the other part about completely rewiring needs a lot of calm thought. This is a monumental job on any coach, probably twice or three times as much on yours as mine.

I don't think you are remotely aware of what a big job this is even if you have loads of electrical wiring experience. I doubt that you have enough time between gigs to do this.

I have given this much thought during times of electrical frustration but in calmer times it is very apparent that this is foolish, unless the coach is stripped bare, and a huge job even then.

Once you get the alt back on line you will probably forget all about this idea.

On my bus I traced down and solved each of these little aggravations one at a time, and it took me a long time. I still have one once in a while but nothing like the number I had the first two years.

Sometimes the best thing to do is just bypass an old circuit completely and string new wiring. However, this is not an easy job and very difficult to do neatly.

[Blacksheep]

I had a pro re-wire my 01 Eagle from front to rear, top to bottom with new EVERYTHING, to the tune of  $3,000.00.
Took him a while too if I remember right! Not something I would want to do! I'll just keep calling Jack whenever a problem or question comes up! Sure hope he doesn't change his number on me! LOL

Ace

[gus]

Ace,

That was probably $3000 well spent.

I'm too old and feint-of-heart to try a job like that!!

It would be really comforting not to have to worry about old insulation coming off and shorting out and corrosion shutting down circuits!!

[buswarrior]

Until you have diagnosed the causes of your electrical troubles, it would be best to not start jumping too quickly on a course of treatment.

You are causing some, if not all of them, by running a significant unbalanced load on your charging system.

As you have discovered, you are destroying batteries, and I will suggest you are pounding the crap out of your alternator in the process.

Either get an equalizer pronto, or the other route might be stripping the 12 volt stuff off the coach batteries and return that system to normal , add a 12 volt battery/bank and a 12 volt alternator to an unused pulley on the engine.

A coach re-wire won't fix this.

happy coaching!
buswarrior

[Sammy]

How are you making out with your repair?

[artglass]

 I am having basically the ame problem , ia called mci they told me the first thing is to clean up all terminals and grounds on all  circuits related to the charging system, , then check the pos terminal on the regulator, then the field terminal.  make sure the ground  on the regulator is good. The regulator field terminal tells the altenator what to put out, if the regulator is not working correctly which means the field terminal should always have 5- 11 volts  the alternator will not put out on the r terminal. If you don't have voltage on the pos  terminal  on regulator which is in the passenger rear bay check your filed relay circuit which is located in the rear j box which is behind the tag axle on the drivers side , you will need the wiring diagrham for your coach.i would check voltage coming out of the circuit breaker feeding the raly first, then the ground on the relay, whcih is hooked to a low air pressure switch, i would go directly to ground and by pass the switch..
    Kevin

[ilyafish]

sorry for the lack of updates, dont have internet often on the road.  we had pretty much traced it to a bad alternator or bad voltage regulator.  which one was it?  Neither!  the wire off of the 'R' terminal on the alternator just snapped and was loose, so after reattaching it, everything was good and well!

Glad that it was a 25 cent repair and not a $200 or $2000 dollar one!

[buswarrior]

Terrific!

Now get that system back in balance.

happy coaching!
buswarrior