Many later model 30 amp Fleetwood class A’s are set up to have two Automatic Change Over (ACO) relays/solenoids. A quick way to tell is to look at the generator, if it has two output circuit breakers, 30 and 20 amp, you probably have two ACOs, one for the MAIN 115 volt power and one for either the rear or front A/C unit. ( On my 99 Southwind, its wired to the rear A/C unit)
The MAIN ACO is an open frame solenoid contactor located inside the 120 volt circuit breaker panel/box, burred directly behind the 12 volt fuses. This ACO supplies the motor homes MAIN 120 volt circuit breaker panel from either the generator or the pedestal shore power. The generator is the priority and the ACO will energize and switch over to the generator whenever its supplying power on its 30 amp output circuit.
One of the A/C units has its own dedicated ACO, this can be wired to either the front or rear A/C units. On my 99 Southwind, its wired to the rear A/C unit. This ACO is a large black box usually located behind or beside the circuit breaker panel. This is the one that many people think is their MAIN ACO, its not. When on shore power, my rear A/C unit gets its power from the main circuit breaker panel (Circuit breaker labeled ECC). However, when the generator is running, the ACO senses 120 volts coming from the generators 20 amp circuit and switch over to it. When this happens, my rear AC unit is now being powered directly from the generator, not through the normal 120 volt circuit break panel.
REPLACING THE MAIN ACO
Tools needed were a couple good quality Phillip and straight blade screwdrivers and a long nose pliers.
Remove all power sources from the coach. Physically disconnect the chassis and coach batteries, DO NOT rely on the disconnect switches. Unplug shore power cord.
Remove the 12 volt fuse and circuit breaker cover plates
Remove two Philip screws in the corner holding the 12 volt panel in place. It will swing out of the way exposing the ACO solenoid underneath.
Take several photos of the ACO wiring from different angles. review the photos to ensure you can see all the screws and connectors.
There isn’t enough slack in wiring to remove the solenoid, so all the wiring must be removed before the solenoid can come out. Fortunately, the large wires have fork connectors, so this will make re-installing a little easier. I removed all the screws from the terminals and reviewed what wires were attached and how they were routed.
When installing the new solenoid, I attached all the wires but didn’t tighten anything until everything was mounted and in place. I reviewed the wiring against the photos, then tightened everything.
LOST PARTS – 🙁
T
he solenoid I used has a feature called Mag Blowout. this supposedly suppresses contacts arcing when contacts change position. This is done with a large ferrite bar installed between the contacts. After I was finished assembling and starting to clean up my tools, I found a long metal bar on the floor. I never seen anything like this so I knew it had to come from the new solenoid. After looking at photos very carefully, I verified that the bar was indeed the ferrite bar and somehow had fallen off of my new solenoid.
If you get the “blowout” version of the solenoid, keep an eye out to make sure the bar doesn’t fall out. Is the “blowout” version necessary. Probably not, the original solenoid didn’t have it and it lasted 20 plus years.
Thanks so much for the info and breakdown of this system! Curious… have you replaced the Converter Charger on this RV? Do you know Model # it is at least?
Mine got water damage and is fried. Thanks in advance..been following your posts for years.. I have a 2000 Southwind 36T
Yes, I replaced mine a couple years ago, the model number and a link is in this article
https://www.1999southwind.com/12-volt-power-upgrades/
what are some common issues this would cause if it were going bad?Is there a reason you didn’t replace the other one also? Thanks
Bad contacts causing higher than normal currents. A visual inspection showed that the lower right contact was heating up (discoloration of the lug connector)
The other changeover is for the rear A/C unit also, It handles a lower current (rear A/C unit only) I haven’t had any problems with mine.
Thank you for all the information you have supplied on your web site, It has helped me out tremendously with my 2000 Southwind.
New owner of a 99 pace arrow 34n that is very similar to your rv, almost identical it seems.
i have the same generator. I replaced the plugs, filters, and overhauled the carb. It runs, but i cant seem to power the RV. I havent checked the brushes etc that you noted in your gen service link. if i understand correct this gen will run without producing electricity.
Ive never used the generator and im assuming this type doesnt require using the shore power cord to plug into an outlet on the rv (i dont seem to have an outlet near the generator).
Im not entirely sure how to approach testing what might be going wrong.
Do you recommend replacing the AOC anyway? And what would you look at or test in your rv if you had the same issue?
thanks for the site, its been helpful with some things
I was considering converting my 03 Southwind 36E from 30 to 50 amp service, but your post on the gen set 20 amp plug is perfect and much cheaper. I cannot currently use my water heater on electric if both ac units are on (trips main 30). Hopefully this is the solution.
My question, I have a constant “clicking” sound behind the main electric panel. It sounds like a failing relay. I have assumed it was one of the ACOs, but can never duplicate it with panel out. I have noticed that the SHED feature sometimes sheds both a/c units. Any thoughts (or direction to the correct forum) would be greatly appreciated. Great site, thanks for sharing everything.
I doubt the clicking is from the ACO. From your symptoms, it sounds suspiciously like the Intellitec thermostat. This is a common problem.
Take a look at this, I sent you my phone number, call me..
https://www.1999southwind.com/replaced-failed-intellitec-dual-thermostat-ecc-with-waiter-ecc-thermostat/
Hate to bother, but when on shore power both ac’s work, it takes some time and they shed a lot. But when on the generator the front ac will not come on for some reason and I cannot decipher from your excellent post whether or which ACO this might be if that’s it or not. Otherwise, everything else seems fine. Any thoughts, also it seems that this coach doesn’t have an ATS, just the Solenoids? Correct? 1999 Southwind 34N
Verify the circuit breakers on the generator are ok.
You may have a bad ACO,
Thanks for the reply. I have an Onan Gen and it only has one 30A breaker, seems OK.So, would that point to the Main ACO? Can I check that somehow?
I don’t know????? I thought 5500 watt genny was standard. These have two genny circuits,, a 30 amp and a 20 amp.. The 20 feeds an A/C unit through itsd dedicated ACO.
The main ACO should be on the 30 amp feed by the 30 amp genny circuit.
Was the generator replaced??
Has the motorhome always done this or did it just start (A/C unit not working on generator)
I bought it used and this is my first attempt at the AC units. The Gen may have been replaced, good chance because I have also a 97 fleetwood pace arrow and it has what I would consider the stock Gen, with two breakers, so ya probably. That may mean I’m in trouble. I’ll replace the ACO and see what happens. Any idea where the second ACO is located and what it looks like?
Download and print the simplified diagram for how the A/C units are wired from this article.
Then call me. I can talk faster than I can type.
I’ll call in the morning. I went to bed right after I posted this morning. Thanks
BTW, it’s only the front AC that doesn’t work on Genny, the rear works with both shore and genny.
Great and thanks. I don’t have your number, and I work graveyard in Oregon so what is a good time to call?
Here’s one for the thread; I replaced the ACO precisely as mine was in place, carefully checking and rechecking the wiring to get it right, After finishing the problem is still there. I hear an audible click when I turn off the generator with both ACs engaged and when it clicks the front ac comes on. I started wondering since this sounds like it is working exactly the opposite way it should if the switch was in backward. Sure enough, if I compare my photos to yours the ACO is hooked up backward. That’s how I got it, now; do I dare hook it up differently, I can do it, shouldn’t be too difficult considering the way they are designed, but should I? Hummm. I need to call you this week if that’s OK?
The only difference with hooking up backwards, shore power will have priority. You can verify this. Disconnect shore power and run the generator. Turn on an A/C blower and it should run. Then without turning off the generator, connect shore power. It should changeover to shore power.
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Thanks for updating the diagram! Currently installing a Victron Multiplus, and the wiring needs to be connected to the transfer switch. Do you know what each wire is on the solonoid? Need to go from the AC out of the transfer switch into the Multiplus. Thanks for the great website!
i HAVE SOME BATTERY/ BATTERY DISCONNECT ISSUE. sORRY i’M BLIND.
aNY INFO,WFOR ENGINE MOTOR SSIDE, NOT CHASSIS OR aUX SIDE. WIRING DIAGRAMS,,,,,,,,,,,,ANYTHING WOULD HELP.
tHANK YOU
mICHAEL
650 219 2636
The battery disconnects are part of the Battery Contrrol Center (BCC) .. You may want to look at these articles
https://www.1999southwind.com/bcc-coach-battery-disconnects-immediately-after-its-connected/
https://www.1999southwind.com/replace-battery-isolator-solenoid-in-the-bcc/
https://www.1999southwind.com/chassis-battery-disconnect-doesnt-work-coach-disconnect-ok/