It may be time for a new A/C and I have a coupla questions ...

[mayfair]

Last year the thermostat went, and now last weekend the a/c was once again not working.  I have a guy coming out to look at it, however just to prepare myself for the worst, I'd like to ask a couple of questions.

First off, my a/c (on my 1999 camper) is a NON ducted rooftop unit with the controls mounted right up there (not sure of the type unit right now). The a/c blows out of either end of it.

Questions

1. If I need to replace the entire unit, what type should I get and where should I get it?

2. Can I do this myself?

3. Most importantly - If I have to replace my unit, I'd like to somehow tie it into a thermostat of sorts that turns the entire unit off when it's not needed, similar to some of the newer units that are out there.

- Is this possible?
- Can this be easily done?
- Perhaps a unit already does this?

The reason that I'd like to do this is since my camper primarily sits on a seasonal site with occasional trips taken, I'm on the hook for the electric bill. When I turn my a/c on now, it runs all of the time (not necessarily the compressor - usually just the fan - but it's running ) and consuming electricity.

All help is appreciated - Thanks!

 

[Mopar1973Man]

Have you try to see if there is replacement parts made for your A/C unit? Since you didn't list a make and model I really can go hunting to see if they do...

 

[mayfair]

Not yet and unfortunately I forgot to write the info down before I left the campground. I'll get the info this weekend though. I'm just trying to be as informed as possible before the repair man comes out.

 

[IrishBrewer]

I added a rooftop AC unit to my previous camper and it was not difficult.  They are a bit heavy and bulky so you need a good way to lower the old one and raise the new in a safe manner.  Since there is already one there, you will just need to take note of the wiring to replicate it when you hook up the new unit.

As far as hooking it up to the thermostat, it can be done if you have a thermostat with a heat and a cooling setting (or just replace it if it doesn't).  However, to get it to work with the thermostat requires some wiring and a relay wired into the AC unit that will act as the on/off switch now controlled by the wall thermostat.  You can see one such modificaiton in the link below:

http://www.modmyrv.com/2010/07/21/rv-coleman-mach-iii-thermostat-modification

 

[COMer]

Any chance that your unit has the ability to shut off the fan when the A/C is not calling for cooling?  The newer ones have a switch that says "auto" or "fan".  The auto means the A/C turns the fan on when it is cooling and the "fan" position means that the fan is on all the time and the A/C just cycles on and off as cooling is called for.  If you have something like that, you could set it so the fan is not on when the A/C is not.  But keep in mind that the bulk of the electricity is used when the A/C is on and especially when it cycles on.  Having just the fan on would take a lot less electricity than the A/C.

 

[SeilerBird]

There are a bunch of A/Cs that will fit right into the existing hole in your roof without modification. You could get a model that has a remote thermostat and run the wires exposed on the ceiling and wall.

 

[mayfair]

I added a rooftop AC unit to my previous camper and it was not difficult.  They are a bit heavy and bulky so you need a good way to lower the old one and raise the new in a safe manner.  Since there is already one there, you will just need to take note of the wiring to replicate it when you hook up the new unit.

As far as hooking it up to the thermostat, it can be done if you have a thermostat with a heat and a cooling setting (or just replace it if it doesn't).  However, to get it to work with the thermostat requires some wiring and a relay wired into the AC unit that will act as the on/off switch now controlled by the wall thermostat.  You can see one such modificaiton in the link below:

http://www.modmyrv.com/2010/07/21/rv-coleman-mach-iii-thermostat-modification

Thanks for the suggestion and the heads up about the weight!

Any chance that your unit has the ability to shut off the fan when the A/C is not calling for cooling?  The newer ones have a switch that says "auto" or "fan".  The auto means the A/C turns the fan on when it is cooling and the "fan" position means that the fan is on all the time and the A/C just cycles on and off as cooling is called for.  If you have something like that, you could set it so the fan is not on when the A/C is not.  But keep in mind that the bulk of the electricity is used when the A/C is on and especially when it cycles on.  Having just the fan on would take a lot less electricity than the A/C.

No, unfortunately my unit runs all of the time when it's turned on. Usually it's just the fan, but yeah, it's running. It's a blessing and a curse as the sound of it running helps to put me into a deep sleep, however because it runs all day the meter keeps spinning.

There are a bunch of A/Cs that will fit right into the existing hole in your roof without modification. You could get a model that has a remote thermostat and run the wires exposed on the ceiling and wall.

Any suggestions for places to shop for one?

Thanks!

 

[John From Detroit]

First the existing A/C is in a 14" Square hole,  The new one will also fit a 14" square hole.

Can you do it yourself.. If you get one with all the controls in the unit, like the one you have now, there are only 3 wires, One black, One white, and one green or bare, that hook up very much as they are hooked in this unit.  Likely they hook to color coded terminals or wires, Same colors if wires, (Well Green for bare) if terminals silver is white, copper is black.

HOWEVER,, I do not recommend doing it alone, Get help, heavy and if you drop it it's back to the store with your check book.. Or hospital with your broken body,, Or worse.

If you wish to add a remote T-Stat, then we have options. Depending on what they put in when they built your rig

They may have already installed wires for a T-Stat.. Or not

If not you are going to have to figure out how to run 'em..  Once that's done there is no problem.

As for turning it completly off... Modern units may have an "Auto" option for the fan that turns it off when the compressor stops (Well a short time later usually)  It does not matter if it's ducted or not, if you use "in unit" thermostat or a remote one, it's all in the A/C control board.

That said. I very strongly do not recommend that, very annoying when that noisy thing kicks in, but not so bad if you just let it run all the time.

 

[Luca1369]

I replaced my rooftop a while back and I did it myself.  I used a large overhanging branch to loop a rope over for the purpose of lowering the old unit and hoisting the new unit.  I had to add a short line to each one to pull it onboard since the branch lowered and raised the load from a spot right next to the rig.

 

[mayfair]

I replaced my rooftop a while back and I did it myself.  I used a large overhanging branch to loop a rope over for the purpose of lowering the old unit and hoisting the new unit.  I had to add a short line to each one to pull it onboard since the branch lowered and raised the load from a spot right next to the rig.

I'm going to head on down this weekend and I think that's how I'll get the old one down as well. I'm still trying to find the best place to buy a new unit from though. Any ideas?

 

[Luca1369]

I'm still trying to find the best place to buy a new unit from though. Any ideas?

I can't help you there as I puchased a lightly used unit. I would google RV air conditioners as a start.

 

[toms57]

I bought a second unit this winter from  a local dealer and they gave me a better price than any mail order seller.  They actually gave me an even better price when I decided to let them install it for me. 

I am thinking to put a 110V thermostat to control the main power so I won't have to listen to the fam when the AC is not called for.  Is there any reason why not?

Tom

 

[Alfa38User]

..... I am thinking to put a 110V thermostat to control the main power so I won't have to listen to the fan when the AC is not called for.  Is there any reason why not?

Tom

This may not apply to a roof air unit that has the controls on the unit itself but....

The operating voltage of the thermostat has nothing to do with what it controls. In an RV's  12V thermostat, 12V is sent as a signal to the  air conditioner to turn it on. This 12V signal  operates a relay which then connects 120V to the unit needed for it to function.

Most thermostats I have seen (including mine) have a Fan Control "Auto" position which causes the fans to switch on only when  required. If the Hi-Low positions of that same switch are used then the fans will run all the time.

On the other hand, a 110V controlled thermostat will not function for anything (including the furnace) while travelling down the road or while boondocking  unless the generator is being used. They are 12V for a reason!!!

 

[toms57]

My thoughts about the 110V thermostat is to leave the controls on the main unit as  they are and to have the new thermostat just shut off the power to the unit when the set temperature is reached.  The unit won't function if we are on the road anyway, just when hooked to shore power or I am running the generator. 
The upside to this is that when it is cool enough, the whole unit goes silent until it warms back up some.

Tom

 

[mayfair]

Ok so here's the latest update ...

I went down this weekend and I was referred to a guy who's been in the RV repair business for 30 years by the local RV shop (they only repair RV's that are brought to them and I was hoping to find someone to come out and repair mine on site).

The guy came out and determined that my unit was shot. He said that even though the compressor came on, that it was probably low on freon and since it's a sealed unit that it is now shot. They can't be recharged. He said that the dealer may have a few used units for sale and recommended that I try that.

I went that route and bought a used unit for $200. I brought it back and it was really easy to install - a LOT easier than I thought it was going to be. Four bolts and three screws and it was off. Simple! I let it sit for an hour or so as was recommended and I fired it up. It ran, however it never really got ice cold at all. It really didn't feel much (maybe a little ) cooler than the unit that I took down.

Grrrrrr!!

So now I'm thinking that the only thing left to replace is the thermostat which is operated by the control knob. Any ideas on where to get one? I have a Coleman Mach A/C if that helps.

Thanks!

 

[captsteve]

How hot is it outside where you are?

I have a coleman mach and when it's in the high 80's I can run my DW out of the camper and hang meat!

The coleman website lists parts and dealers...

 

[Mopar1973Man]

Same here I've also got a Coleman A/C unit last time I check the vent discharge temp with a thermometer it was 42-45*F on a 85*F day. I would talk to the dealer you got it from and also check the discharge temperature and see how its doing in performance.

 

[Gary RV_Wizard]

Sounds to me like you bought a used a/c that was no better than the one you have. Did you just buy the upper half and did not get new interior portion (including controls) with it? Or was it a complete a/c.
If the compressor comes on and runs,  changing the thermostat controls won't do anything for it. If the compressor is not cycling on, then the problem is in the controls but still may not be the thermostat portion. The t-stat just signals "cooling needed" or "temp ok". It's the rest of the control logic that starts the a/c fans, gets the compressor running, etc.

 

[mayfair]

Sounds to me like you bought a used a/c that was no better than the one you have. Did you just buy the upper half and did not get new interior portion (including controls) with it? Or was it a complete a/c.
If the compressor comes on and runs,  changing the thermostat controls won't do anything for it. If the compressor is not cycling on, then the problem is in the controls but still may not be the thermostat portion. The t-stat just signals "cooling needed" or "temp ok". It's the rest of the control logic that starts the a/c fans, gets the compressor running, etc.

I bought the top portion only, not the interior part.

I think it's the t-stat now because it really is the only part left in the puzzle. I think what is happening is that the t-stat calls for it to come on, but then "thinks" that it has reached the proper temperature and then shuts the compressor off.

Outside temp was about 85 or so, and the coldest that the a/c registered at the vent (using an a/c style thermometer) was about 67 or so. It dropped it, but IMO not enough. It used to get a lot colder and that is why I now think that it is the t-stat.

Agree?

I'm now wondering if I can somehow tie the rooftop a/c into the t-stat on my wall that I use to control my heat?

Thoughts?

Probably too much agg.

The coleman website lists parts and dealers...

I couldn't find a website for Coleman, but I wonder if this is the right part?

http://www.americanrvcompany.com/Coleman-6703-3401-HeatCool-AC-Thermostat-Camper-Trailer-RV_p_10466.html#

 

[Icemaker]

OK I got to jump in here....
First I'm a retired HVAC/R service tech...that being said..
Yes it's a sealed unit and NO it can be serviced and re-charged...but might not be worth doing..
The USED unit you bought was probably [used] for a reason...sorry pal...
Most a/c's should discharge air around 15-20 degrees colder than room temp..colder means not enough air flow across the coil, read dirty or restricted flow or fan speed too slow..
If it is much warmer discharge it is usually due to a low charge but can be the load is too great or the fan is too fast[shouldn't be that but if the air doesn't stay on the coil long enough the BTU transfer won't happen].
As for the line voltage thermostat I see no reason why you can't use one..just remember it has to be rated to handle the amp [wattage] of the unit including the starting surge AND it has to be a COOLING thermostat..most line voltage t'stats you'll find in Lowes or such are probably for heating...you want the switch action to BREAK on a temperature drop...heating ones MAKE on a temperature drop..
Most a/c's are not designed to run a room much cooler than 70 degrees [I know some go to 60 but they are way beyond their design]
Also FYI when an a/c first starts as much as 80% of it's load is the moisture in the air and will at first seem less effective...so keep windows closed and o/s air infiltration to a minimum and let the unit lower the room humidity.. as the humidity level drops you will be more comfortable and the temperature will drop.
I could/can never convince my Mother to close windows..wants to let HOT AIR OUT..and I'm full it...sigh ...
Another ALSO...the newer units operate more efficiently and usually have fan auto/on  controls..so if you decide to replace the replacement, sorry for that, look long and hard at biting the bullet and good luck..
Sorry about the soap-box and hope I don't offend..

George