RV roof A/C trouble shooting:
 

I am recommissioning my old 1982 Airstream RV and the rooftop A/C units are not working. When I bought it in 2020, one of the two worked but now neither goes on. It seems to me that I've read previous threads here about home A/C units where some simple component caused the compressor not to fire up, I'm hoping to benefit from knowledge here and not have to bring it somewhere...any advice on what to check or look at? I know next to nothing but I do have a multimeter and test light.

Major thanks in advance. It's supposed to hit 103 here today, first real heat wave of the summer. I want to take the RV to the beach! :cool:

Low on freon would be my first guess.
Second would be electronics.

Is that a 120v AC unit? Motor start capacitor or relay? The low on freon as Arizona mentioned.

What brand are the units? Assume you are hooked up to 30amp service and have power (checked circuit breakers etc) to the thermostat and the unit itself? Does the fan come on when just in fan only mode?

In a home AC unit typically the compressor motors use a capacitor start system. When they fail to run it can often be as simple as replacing the capacitor but I am not sure about your particular AC units.

My 2004 coach AC units sometimes take several minutes before they start up after turning them on at the digital thermostat wall mounted controller. IAt first I thought they were not working but they always start eventually.

Went through this when my brother visited in his RV and A/C quit on his. We went on line and did some basic research and ended up changing out his start capacitors that were originals. Also some wiring connections were a bit corroded and or loose. Believe we found the caps at auto parts store or maybe the local RV dealer,not sure. There are quite a few educational U-tube videos out there as well. Good luck!

Here's a couple sites that might get you headed in the right direction:
https://evapolar.com/blog/air-conditioner-does-not-keep-rv-cool/
https://www.fulltimefamilies.com/rv-ac-repair-guide/

Are the AC units the ones from the 80s or more recent dometic style units? "neither goes on" is also kind of vague, much like "car won't start." To stick with "car won't start" analogy is this
1) I turn the key and nothing whatsoever happens (maybe no power/fuse/thermostat wiring issue)
2) I turn the key and the lights on the dash light up but nothing else happens (maybe thermostat or capacitor issue)
3) I turn the key and I hear a click click click but nothing else (maybe a compressor seize issue)
4) I turn the key, the engine starts but dies (OK analogy dies here but you get it, running but not cold is maybe R134 issue)
etc etc

Yes, 120v units. I’ll remove the covers and take pictures so that you guys can help me identify the parts.

See if the evap coil and condenser fans spin freely and don't have stuff in them.
Sometimes there is a condenser high pressure cut out switch that opens and can be reset.
Check the motor contactors and the start capacitors.

They each have dial controls and they do not turn on. No fan, nada.

As noted, most A/C issues where the compressor does not run is the start/run capacitor...although a bad compressor or the compressor thermal cutout switch (in the compressor will keep it from starting). In my experience, a bad compressor typically pops breakers as it shorts to ground...so more obvious.

The caps (usually one for the compressor and one for the fan) are easy to test and often you can tell just by inspection (bulges or leaking). If the fan doesn't run, the compressor may cut out (thermal cutout). It does not reset until the compressor is cool.

You likely have a 120v contactor of some sort. It is just a big relay. When on, you should have 120V on the input and the output (as measured across the input/output leads). I start there with an A/C unit where nothing works. The contactor in most home units (they are 220) allow you to manually close the contacts which should turn on the fan and compressor while you hold it.

Check for mice.

The primary things that goes wrong on Air Conditioning units is loss of freon followed by a dead capacitor and then the motor contactor. I keep spares for those fixes, because the AC always goes out on July 4th or Labor Day weekend...

A compressor that is low on freon will usually run (fan and compressor), but not cool the air.

On a similar note, my boats freezer quit a few weeks ago. I was dreading it because it meant, as a minimum, emptying out a storage locker and contorting into a cramped space to diagnose the fridge unit. And worst case, $1300 for a new unit, plus installation.

But there a lots of good diagnosis checklists on line. For an older unit especially, because there has probably been lots of DIY repairs posted over the years. Look up the model and do a search. You may be surprised what you find.

In my case I dodged a bullet. First item: Verify power to the unit. When I got to the unit I could see that one of the power wires was pulled off of its connector. Reconnected and off she went. I was so happy. Boats rarely give a freeby.

If you can't run the fans in FAN mode, I'd start with checking for power to the units, first.

These units are usually simple, shoot some detailed photos and we can show you what to poke and prod. The circuit board, or what passes for one in these units, might be accessible from inside the RV, where the air duct is.

Thanks, guys. It’s too hot to climb up on the roof of it today, (I’m at the beach), but I shot a couple of the interior part of it before I left. I might be able to climb on it tonight.

http://forums.pelicanparts.com/uploa...1725581765.jpg
http://forums.pelicanparts.com/uploa...1725581765.jpg
http://forums.pelicanparts.com/uploa...1725581765.jpg

I would start by seeing if you got power to the board and then going from there.

There's the problem. You are running it in the "OFF" mode.

Sheet, it's a 1982 unit? just replace. simple.

Not if they are still good. One of them was working great when I bought it in 2020 and the other did not turn on. Now, after sitting for 4 more years, neither go on. If they need to be replaced, I will replace them but first I need to determine what's up. :cool:

Never knew there was an Airstream RV like this, that thing is badass!

I'm gonna guess that if the fan does not run when it's set to 'FAN ONLY', then you have a failed fan, or more likely, no power to the unit.

Does the fan come on?

Next I would check voltage at the compressor. Zero volts? Probably low gas pressure. Find the pressure switch.

I need to get up on the roof but it's just too damn hot here...over 100 degrees. I honestly don't know how people in the hot parts of the country survive without an ocean to jump into...I'm hanging at the beach until next week when the weather changes. :cool:

Yesterday, first two @ Will Rogers in Santa Monica and last one Malibu:
http://forums.pelicanparts.com/uploa...1725651186.jpg
http://forums.pelicanparts.com/uploa...1725651186.jpg
http://forums.pelicanparts.com/uploa...1725651186.jpg

Thank you guys very much for the help! I'm going to climb up on it soon. :)

Update:
 

I went over and poked around a little on it and the front unit still works like it did when I bought it but the rear does not. I checked the main breakers in the coach and found the switch for shore vs. generator power, it was in the wrong position and when I flipped it, the unit turned on. Blows cold but I still want to service it if possible. I took the big cover off of it and it needs a good cleaning at the least. Lots of pine needles and dirt under the cover.

So what am I looking for on the one that does not turn on? What does the start up capacitor or whatever it's called look like and where might I find it, if anyone knows? I took some photos:
http://forums.pelicanparts.com/uploa...1725693417.jpg
http://forums.pelicanparts.com/uploa...1725693417.jpg
http://forums.pelicanparts.com/uploa...1725693417.jpg

Also, the generator, which has always started right up and sounded good, seemed to be straining powering just one A/C unit and started smoking visibly...I shut it down when I noticed. It's a standard Onan unit found in RVs but it runs on LPG instead of gasoline because my RV is a diesel. On the gas Airstream RVs, (much more common), the generator ran on gas. I can change the oil and check the air filter but I really don't know what else to check or service on it(?)

Granted, it was over 100 deg. today but if the generator can't handle that, (powering A/C units on a hot day), what good is it? I cannot see how it cools itself...is there a fan in this thing somewhere? All knowledge apreciated!
http://forums.pelicanparts.com/uploa...1725694022.jpg

Just follow the wires from the compressor back into that box on the left. You should be able to remove a couple of screws to get into the access panel/cover. The capacitor is usually shiny and a little smaller than the size of your fist (with wires going into it). Probably have one for the fan and one for the compressor.

This video might help. It shows a fellow replacing the fan capacitor. Looks like one for the compressor is right next to it.

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Might see it better on this parts breakdown:

https://youngfartsrvparts.com/pages/coleman-mach-1-el-air-conditioner-product-id-6744a901-parts-list?srsltid=AfmBOooay6zMGoLZGj8UgYlratbr8GRMd90bv wJ-wQ69x537EiFAZZ6f&shpxid=75490701-e96a-4003-9342-bd31a18bc898

I believe the cooling fan is inside that square housing on the left in your pic . It pulls air across the engine/head/oil filter . So air flow is left to right when looking at the unit .

Could you tell where the smoke was coming from ? What color smoke ? When these sit it could be as simple as bugs/bees built a nest to mice built a nest to dirt/leaves build up or mechanical like stuck piston rings .

I think you will need to pull some cover plates or whatever you can to do a good visual inspection . Also because of the age every wire needs to be looked at for cracked insulation and rodent damage . Cool rig good luck with getting her going .

There are probably 3 capacitors. Most likely they will be located behind a removable cover (the galvanized sheet metal on the left side of the compressor in your picture.). Turn off power to the unit, take notes of which wires go where on the three capacitors, remove the wires, discharge the capacitors, remove them and take them to a new supply house to have them tested.

There is probably a thermal cut out under the little cover on top of the compressor, test it to make sure it’s OK, first.

If you don’t know how to do any of that, YouTube is your friend.

Of course, my advice would be to first find the circuit board, which will usually be located by removing the grill inside the RV, and looking up into the area next to the evaporator. I would make sure you have power coming to the unit, that I would test, the thermostat wiring to see if it is calling for cooling or the fan to blow, when you try to run it.

If that all checks out, then get up on top and to see if the fan turns freely and has no free play.

If that’s fine, then check out the thermal cut out and the capacitors.

You did check the oil in the genset prior to starting it, right? Who knows what happens when stuff sits for a long while.

Many AC have a largish relay to manage the startup current. I'd look for one of those too. Wouldn't be surprised that one would stick after sitting so long. I'd start with that and move on to the start capacitor.

The other symptom is the fan won’t run…

Start at the beginning…

Hey Denis, buy me a plane ticket to LA, a hotel room in Santa Monica and all the sushi I can eat and I’ll come out and fix this for you.

Air cooled generator + mice = blocked air flow. That's my first guess. The inside probably looks like the AC units.

The governor linkage is next, it should run at a fixed rpm (3,600?) to make 60 Hz power.

A meter that can measure voltage and frequency might help you down the road.

Thanks a million! I did not check the oil in the generator yesterday but I've checked it in the past and it looked clean and proper level. The entire unit is going to get a proper servicing now before I start it again. It's always fired right up and sounded great but I haven't been loading it up. I will remove all cladding and look for debris.

Fint, thanks for the videos and Java, I'll keep your offer open! SmileWavy

I have had a gas powered Onan and my current rig has a diesel powered one. While not your issue, my gas one hated any gas with ethanol. In the rare occasion is used gas with ethanol I always drained the bowl before parking it.

Good points on just taking things apart and looking at the airflow. For mine they did not recommend running them without the covers on as it affected the airflow. They are pretty sturdy and while AC's pull a lot, if it was struggling getting it serviced is a good idea after you check for blockages.

Yeah start with the basics and get out a meter and see if you are getting power there at all.