roof top a/c help

j-d wrote:
Thanks, Chris,
Sometimes Radio Shack really comes through on that kind of stuff. I had a friend who was ready to junk a marine fridge because the manufacturer showed the Relay as NLA. I suggested Shack and he found one that fit and worked.

Are any Radio Shack stores still open?

"These are the stores RadioShack is closing."

Thanks, Chris,

Cleaning is never out of order. Applies to the Blog, too, eh?

What kind of relay is on the Board? It seems there's the "Bosch" cube shaped one and recently I ran into the "Siemens" that does the same thing (if it's SPDT like Bosch...) but in a more rectangular form factor.

Sometimes Radio Shack really comes through on that kind of stuff. I had a friend who was ready to junk a marine fridge because the manufacturer showed the Relay as NLA. I suggested Shack and he found one that fit and worked.

j-d wrote:
Chris, I can't get to the "Tech - Tune Up Your Rooftop A-C" article. Is that still available?

Kind of- http://blog.goodsam.com/?p=1160, but they took my name off it, and didn't move the pictures.

The blog has been a mess for a while- I believe they are trying to clean it up a bit.

Back to the OP, the reason I say upper circuit board is that the compressor keeps running until he shuts the breaker off- classic sign of a compressor relay with the contacts welded closed.
Not that cleaning is ever out of order :).

Chris, I can't get to the "Tech - Tune Up Your Rooftop A-C" article. Is that still available?

This Cleaning Process is not the same one Chris Bryant put on the RV.net Blog but it's the same gist.
BREAKER OFF before you climb to the roof!!!
Be careful you don't damage the roof skin with tools and parts, also by not twisting your feet as you move around.
The sheet metal "nose" has to come off but you'll be right next to it with Jose's Capacitors. When you get to a Capacitor, short across it with a screwdriver you're holding by its plastic handle. That'll drain the charge from it. OK.. the A/C:
Where the arrow labeled "Drain Pan" ends, there's the slot through the roof that returns cold air to the interior of your coach. You can plug it with towels, allowing you to give that coil a good spraying, down the front, maybe you can reach the back, and through it. Be diligent in finding the Drain Holes.
I use a license plate to deflect water away from the Air Return Slot and flush the fins with my garden hose nozzle. Just NOT a full hard stream!!! Them fins are fragile. Pump-up tank sprayer works very well too and much less water gushing around.
I haven't seen a clogged Condensing Coil. The one in the back of the unit that has a fan in front of it. But you can spray that clean too. In our case, the Indoor Blower, squirrel cage in front of the Fan Motor, was really loused up. I pulled it and cleaned with spray cleaner and garden hose down on the ground.
This'll let you oil both Motor Shaft Bearings. There may be oil holes/plugs, but even if not, you can put some Turbine Oil on the area and it'll help some.

The compressor relay on the upper circuit board is stuck closed. You need a new upper board.

I am told that dirty filters and coils can cause freezing and I have seen SOME support for that theory.... Though it is more likely to cause other issues

Also run the blower on HIGH, The problem is reduced air flow.

Two things that WILL cause freezup:

Many RV A/Cs have a freeze up sensor,this sensor probe needs to be stuck in the evaporator coils..Some have found it lying in the drip tray.


Low Coolant.

^^^ That's right!!! And clean the coils while you're in there. There's a blog entry for that but my link is bad. Will try to find it.

What Brand and Type? Jose and I have Coleman with manual knob controls and no ducting,

Could be the compressor locking up on a restart. Mine was doing the same kind of thing. Then a buddy of mine who does HVAC for a living said the compressors are very reliable and it's almost always a case of bad capacitors when your AC won't kick on.

I opened up my 32 year old rooftop Coleman AC and discovered the capacitors were all leaking. I replaced them and it now works GREAT!

Be very careful when dealing with capacitors. They hold a brutal charge and really can hurt or kill you. If you are unsure about it, see if you can contact a local HVAC guy to come open it up and help you order/replace them.

Jose