[Ken]

I quess I’m confused the original 24v dd alternator was removed by the converter and replaced with a 12v one? Why?

[Michael]

Greg, There was some confusion on my part initially when i was diagnosing the problems I was having with my Electrical system. Earlier in the thread i didn’t know as much about my bus and how the DC side of things, 12 and 24 Volt chassis and 12 Volt house. My Bus Build sheet shows a 50DN 24 Volt 270 Amp alternator, but in fact has a 12 Volt 300 amp alternator Gear driven, which is used to run the Frigi Cool Country Coach version of the Cruise airs. My Country Coach Build sheet shows a complete bus with a 12 Volt alternator, 50DN gear driven which is what I have. the 100amp Vanner was installed to replace Two 50 amp that were wired in Parallel, so I am good from the Vanner standoint. Fast forward a month, with lots of troubleshooting i have discovered this 12 VDC 50DN does not put out any Voltage. The Alternator is shorted to ground Internally which took out the Voltage regulator and the start relay circuit which shorted the yellow ignition wire to ground also. After pondering my inability to find spare parts, and how rare these alternators are becoming I decided to pull it from the engine. I see it as a liability being spun by the cam gear without doing anything. If anything happened to the bearings it could cause damage to the engine internally. Short term i am going to rely on my 200 Watts of Solar and the Generator to charge the batteries until i can install a belt driven alternator over by the chassis alternator. I hope this clears up the confusion. Let me know if you have any questions.

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Mike Harper

2004 Marathon XLII

[Art]

Let’s look inside.

[Archived]

Ok I have about 100 miles on the Bus since I pulled and capped the 50DN, all looking good so far.

[Archived]

Thats good news Mike! Keep us posted on your new charging system.

I finally got a chance to dig into mine further. My access panel was exactly like yours. Unfortunately Marathon decided to carpet the bedroom one peice and set the bed cabinet on top of the carpet. Not only that the panel ran 6 inches under the bed. From looking at your pictures i was able to determine where the buried screws were. i cut some small slices in the carpet to remove them. I had to cut the floor panel in half to remove it.

Once i got in there it was much easier to get to the terminals to troubleshoot the no charge situation. The first thing that i noticed was that there was no ground bar from the field ground terminal to the alt case. Hmm. Every 50dn that ive seen has that including the new one i bought to replace the original. I took the ground bar off the new one and put it on there. I started the bus and the volt meter on the dash pegged to 30v. I shut it down immediately. After doing some further research i determined that my regulator is a low side regulator so it regulates the charging on the negative side of the coil. With a dead ground the coil signals full unregulated charging. I removed the ground strap removed the new regulator that i installed a few weeks ago and put the old one back in and bingo, 28 volts on the dash. My problem turned out to be just a loose connection on the field ground terminal.

Apparently they no longer make a regulator that controls the low side so if my regulator ever dies i will have to change the wiring over to high side regulation.

Yet another lesson in “check your schematics”. Your bus may not be the same. Some times i forget to listen to Jon.:) Has anyone ever heard of a low side regulator?

Im back to a working alternator now. My next task is to modify the panel so to fill in the 6 inches of panel under the bed and make a new one that is only outside of the bed.

I very much appreciate you taking the time to document and share your work. That goes for everyone here who does the same. Thanks guys.

Jeff

[David]

Well Done! Glad to hear a success story.

[Marshall]

This is a fantastic discussion! I recently bought a new regulator for the gear-driven 24v 270A 50DN on my 8V92TA. When I went to convert the 50DN from a low-side to high-side setup, one of the electrical studs broke free internally. I haven’t looked to see what it might take to correct that, but I sat there looking at my alternator and decided to look into removing it altogether. I no longer have OTR air conditioning, and would not want to have to work on this thing again once the bedroom is installed. My bus is currently gutted for a complete renovation.

This may need its own thread, but apart from blocking off the accessory case and oil line, how big of a job is it to convert to a belt-driven alternator? Are mounting brackets available to make it less of a custom installation? I’m flexible in the type of alternator that would go back in, but would like good output in 24v.