AIR CONDITIONER DELAY IN STARTING

[Fred Brooks]

               Hi Leah,

     No problem because we all know life happens..........If the comfort control t-stat is the 5 button (which is obsolete) style, The delay is approx 2 minutes if the t-stat is in AUTO mode. What they don't tell you is if you touch any other button once you have turned it on, you add another 30 seconds delay on top of the two minutes. So if you turned it on and tapped the temp up or down 6 or 8 times you can add 4 more minutes to the delay. No problem, Just turn the t-stat off and back on. If you want to by-pass the initial delay, move the fan switch off of "Auto" to hi med or low and fans will come on right away. The compressor will still have 120 second delay before engaging.
          Temperature differential between output cooled air should be 20 to 26 degrees cooler than return air going into the air conditioner. This temperature variable is based on how much humidy is in the air. The higher the humidy the heavy the air is which makes it harder to cool.

                 Hope this helps, Fred

[Mike Groves]

If the comfort control t-stat is the 5 button (which is obsolete) style....

Fred,

Given that my Tstat is the 4 button, which I have kept alive by cleaning the contacts with QTip and alcohol, it must really be obsolete.  I thought the 5 Button was the upgrade.  Is there now a TStat to replace what I have?  This TStat listens to no less then 2 other sensors (bathroom, and bedroom), as the 5 Button does, I guess.

Thanks,
Mike

[Fred Brooks]

                  Hi Mike,

      The 4 button was replaced by the 5 button, The 5 button was replaced by the 12 button. If you are going to entertain doing the upgrade here are some considerations. If your coach has the 4 button that means your air conditioners are over 12 years old or more. Life expectancy  of the A/C is 10 to 15 years. If you change from the 4 button to the 12 button you will have change printed circuit control board inside EACH air conditioner and rewire some of the wiring at that board. I'm not sure spending the 250 to 300 parts and labor (not including the price of the 12 button t-stat) on each air conditioner is a wise decision. I've done this upgrade over 12 times only to have the air conditioner expire within a year or two.

       Hope this helps,  Regards, Fred

[Edward Buker]

Fred,

I have the 5 button thermostats and have not had a problem, but if I did, what is involved with going from the 5 button to the 12?

Later Ed

[Fred Brooks]

      Hi Ed,

      If it ain't broke, don't fix it. LOL The 5 button is a pretty dependable t-stat. If your going to  make the change, the same things apply as my previous post. I think the only 2 things that will not work if you go to the 12 button is the de-humidify option and the outside temperature option.
      Regards and I enjoy your posts and info, Fred

[Edward Buker]

Fred,

No plan to fix it until it is broke..... Our 2002 Marquis has two rooftop airs which was an option over the basement air for that year. Luckily the original owner chose that option, just think that system is more easily repaired with replacement units. I do see Adventure RV and several other sources of 5 button thermostats out there so I guess one could handle a thermostat replacement for now with available parts. If they are being obsoleted maybe I should buy a spare.

I also enjoy your posts and your broad knowledge and hands on background in so many aspects of RV work...glad you bought a Beaver and joined our forum :-)

Later Ed

[Fred Brooks]

          Thanks Ed,

   Here is probably the way the scenerio will play out seeing your air conditioners are 14 years old. One of the air conditioners will fail either by loss of freon or compressor lock-up or who knows what......When you go to get it replaced, they will advise that the replacement A/C will not communicate with the 5 button T-stat. They will advise that you purchase the 12 button t-stat and the upgrade the PC board for the other A/C that is working ok or they will say why not change both air conditioners and be done with it. Not the story you want to hear but unfortunately that is what will happen, start saving your pennies or if your in Tucson come and visit me. Incidently the 12 button t-stat is a horizonal mount, not sure where yours is located.
               Regards, Fred

[Tom and Pam Brown]

Just replaced the rear unit on my 99Marquis.  The unit works well with the 4 button thermostat that is there......in August I will replace the front unit with a new unit as well.  The difference between the old unit and the new is phenomenal.  The rear has never been that cold since we owned the coach.

There is a guy who rebuilds 4 and 5 button thermostats on eBay.  Very reasonable and mine has worked for over 4 years with no issues.

Great info Fred enjoy reading your posts.

[LaMonte Monnell]

Just replaced the rear unit on my 99Marquis.  The unit works well with the 4 button thermostat that is there......in August I will replace the front unit with a new unit as well.  The difference between the old unit and the new is phenomenal.  The rear has never been that cold since we owned the coach.

There is a guy who rebuilds 4 and 5 button thermostats on eBay.  Very reasonable and mine has worked for over 4 years with no issues.

Great info Fred enjoy reading your posts.


Tom, what A/c did you buy for your replacement. I have one that is super loud and may replace it soon. Thanks!

[Fred Brooks]

       Tom, Do you have a 4 button t-stat for each air conditioner?.......Fred

[Tom and Pam Brown]

Lamonte, I called Dometic and they said the unit that is a direct replacement for mine is 640315CXX10 Model 60184.  Bought at camping world for $680.00

Fred, my 4 button has 3 zones and yes it operates both units.

[Mike Groves]

There is a guy who rebuilds 4 and 5 button thermostats on eBay.  Very reasonable and mine has worked for over 4 years with no issues.

Tom and all with 4 Button Tstats or '99 Marquis,

I was all ready to send my 4 button to this guy on Ebay, but figured it clean the contacts first because another online poster recommended it could be done. 

I removed the unit by unscrewing from the wall and disconnecting the cable, opened it up, and used a QTip with alcohol on the locations where the switch contacts were under each button.  I felt as I was doing this that, "there is no way this is going to work".  I even got part numbers of the contact switches, or attempted to, so that I could see what new ones cost - no luck there. 

So I wondered how this Ebay guy was "fixing" these things.  After returning the unit to the coach, and feeling like I'd done nothing, the unit worked like a champ.  My only guess is that over the years we keep pushing those buttons with dirty fingers and eventually create the problem, which is cleaned up with simple Qtip and alcohol, so I would suggest rather than sending your unit to the ebay guy along with $100 I think it is, that you try cleaning it, then try keeping your hands clean while using it.  Mine's working fine now even after a year since I did the cleaning...not perfect but it was awful before the cleaning in that I couldn't get anything to happen using the buttons to turn the temp up or down.  Now, sometimes, I might bounce a couple degrees, but its responsive.

Anyway, just my experience.  I can not imagine that this guy for $100 can refurb these units, but I bet he has a better cleaning operation than I used, and that's all he does.

So far, Tom, my '99 is cooling well both units, at least according to my wife.  We only run it to about 73 or 74 degrees, so for now all is well.  This coach of mine I am happy to say just doesn't seem to have been pushed that hard in the 65,000 miles or so before I purchased it, and has spend most of its life (until I purchased it 9/4/13) inside.  Now I store it under cover but it isn't inside any longer, so I guess its beginning to wear a bit more. 

I'll close by knocking on wood.

Mike

[Mike Groves]

       Tom, Do you have a 4 button t-stat for each air conditioner?.......Fred

Fred, the '99 Marquis have the 2 roof airs with temp sensors only in the bedroom, and bathroom, and also one for the living room within the single 4 button tstat which allows you to program each ZONE (up to 4, only 3 are used).  I don't see how the cooling is different since we only have 1 air for both bathroom and bedroom, but the heating is definitely independent in all 3 zones.

Mike

[Tom and Pam Brown]

I was somewhat taken aback when I removed the wood panel to expose the rear unit.  I thought the bedroom and bathroom were on the same unit, however, the bathroom is cooled by the front unit.
Once the panel was down it was an easy job.  I spoke to Dometic and they told me the new unit would work with the old control box for the 4 button thermostat.

When I had issues with the old 4 button I bought new control boxes and a new 5 button just in case it failed.  If it does I am ready with the upgrade to the five button.

The amount of air the new unit pushes and quick cool down it was worth the effort.  That's why I will go ahead and replace the front later in August.

The new unit cools dramatically better going down the road versus the old units. 

[Fred Brooks]

              Mike, The sensor (thermister) in the bathroom is for the aquahot I believe and has no effect on cooling. The front A/C is the master and the t-stat and aquahot are connected to that unit. The rear A/C is daisy chained thru a comm line (looks like a phone line) to the front A/C. Inside each A/C from the top side is a pc control board. This pc board has 8 dip switches for various options: ie zone 2,3,4 furnace, ect. Your rear A/C has the zone 2 dip switch turned on so the t-stat knows it has 2 air conditioners connected to it. The front A/C has the furnace dip switch turned on so the t-stat knows it has a furnace or aqua hot connected to it. The original 4- button t-stat required that you hold down the top 2 buttons at the same time for a second to toggle between zone 1 and zone 2 as indicated in the led display towards the bottom of the t-stat window.
        Question, When you use the aquahot in the barhroom, does the t-stat show zone 3?
                Regards, Fred