[bikestuff]

Gang,

I am on the road headed back home.  I stopped to visit friend and left generator and ACs running.  When I came back to coach, I smelled a strong electrical smell and found that all my AC's are dead.  No Power.

Here are the facts:

1)  No display on any of my three thermostats.  (I have never seen this before).  
2)  No breakers are tripped.  I reset all the pertinent breakers (rear closet) with no joy.
3)  Even my rooftop AC is dead.  (That one is powered separately and does not trigger off of the HEAT / AC relay)
4)  Possible red herring....I just left the factory where they ran a new wire to my front AC.  They said it was a dead short in the wire and they ran a new wire to the front AC.  (Did not find the source of the short).
5)  Electrical smell is strongest in the rear basement AC bay.
6) Meters over dash show 120V with no amp draw. (I turned off generator and voltages dropped to 0V as expected)

I have call into 24 hour hotline, but not response yet.

Any and all suggestions welcome.

[bikestuff]

Gang,

Got off phone with Newell.  They found a blown fuse that controlled all the thermostats...but that did not explain smell.

Front ACs now working.

When i pulled electrical box cover from rear basement AC, I found that the board was completely fried.  There had been a small fire in the box.  Picture attached.

AC breakers have now been turned off.

What now?

Cheers,
bill

[Chester Stone]

Bill, perhaps you can study the control box to see where the short started. Hard to believe that a breaker did not trip. Following is a note in my files with information from Tuga and Tom: REPAIR PLACE: National Indoor RV Center, Lewisville, Texas, 469-277-1330.
Near Denton-ask for Eddie

PLACES TO REPAIR CONTROL BOARDS:

SCS-Victory RV & Truck Climate Control, Mechanicsburg, PA 800-403-3728
ACS Industrial Services 800-605-6419
Onlinecomponents.com, Henderson, NV 702-462-7300

[bikestuff]

Chester, I am pretty sure this control board is total loss, as well as connectors on the wires. ugh.

[RussWhite]

Bill,

Sorry about your situation....

I am going to just speculate on what happened as I have had some experience with those control boards.

In my opinion the root cause of many of the AC problems is that poorly designed circuit board. It simply is very marginal in its ability to carry the current of the compressor and fans. Any added current due to a bad bearings, high head pressure, etc puts the board in overload and bad things start to happen. The weak areas are the little lands ( the thin copper traces ) that make it a circuit board, the compressor relay, and the connectors. My boards have been highly modified with new connectors, wires soldered to the lands to help share the current, and the occasional relay replacement when they go bad.

Imagine for a moment how an old space heater works. You look in the front and see glowing red wires as the little fan pushes air across them to make you warm. Well, that is basically a short circuit as that wire is right across the mains. Why does't the breaker trip? - because the resistance of that wire is high enough to limit the current to less than the setting of the breaker. So, in your case I speculate the fault had high enough resistance to limit the current, but 1000 watts of heat in that little box will melt it down, just as your photo shows. In that process, the 12VDC signal from the thermostat got involved and blew the little 12 volt fuse shutting down the front unit which up until then were running along just fine.
I agree with you that the circuit board is a total loss. I have not looked for a source for new boards, but maybe some one else has and will comment on availability. The board is overly complicated due to the requirements places on the designer with the option for running on 30A and only power to one leg. If not for that it would have been much more straightforward and probably could have been designed with larger copper runs and not been all the trouble it has been. Russ

[bikestuff]

Russ,

Thanks for the thoughtful analysis. I believe you are right on all counts. I have attempted to keep an eye on these boards and regularly pull the lid off and inspect for obvious problems. Never have seen any sign of board fatigue until I had a total melt down.

For those wondering, this was more than a simple lead getting hot and causing problems. There was a fire inside the metal box and soot was on the wood shelf above the unit. I came close to losing the entire coach with my two dogs inside.

I will follow up with Newell and see what they recommend.

I am going to renew my effort to find a replacement entire AC unit.

Thanks!
bill

[77newell]

Just thinking out loud: could it be possible to add an extra box containing heavy duty relays actuated by the smallish relays in the control box. In this way the high current loads would be managed by an arrangement easily capable of handling them.

[RussWhite]

Alie,

I think that is a workable suggestion. If you just get the high compressor current off that board completely and pass it through a relay more appropriate to the current the board would last a very long time in my opinion.
I am in my coach year round and with the air on much of the time. If my present mods don't hold up I think I will give your idea a try. Thanks - Russ

[Chester Stone]

Russ, I previously owned an Alfa with a two stage Coleman basement heat pump putting out two tons A/C. If one or both of my die, I will investigate replacing them with Colemans. RV Products handles them. It may be worth a call.

[qcj]

Chester, I owned a coach with a two stage Coleman in 06 and it never work correctly.  Finally sold the coach because of the A/C. I understand Coleman does not make this A/C anymore.