Malfunctioning Coleman Thermostat

[Gadget_Man]

My 2005 motorhome has two Coleman Mach 2 A/C units controlled by a single Coleman RV Comfort ZC digital thermostat.

Two to three times a year, while running the A/C’s, our t-stat will make a popping noise and will instantly give a digital readout of “00”. This effectively shuts off any cooling as it turns off the A/C compressors. It does however allow the A/C fans to continue running. If we are home this is no big deal, as we can reset the t-stat by momentarily turning off the house batteries, but this could spell disaster for our dog in hot weather if we are away.

When this first started happening, I contacted Coleman and got in touch with one of their engineers. The engineer said that although this problem is rare, it does happen from time to time on some RV’s. He told me that there is some sort of 12V radio frequency interference inside my RV, which is causing the thermostat to go into diagnostic mode. He kindly sent me the latest t-stat and radio noise choke filter free of charge. When this did nothing I called him back. He told me the following items could be causing the interference: fluorescent tube lighting, TV antenna booster, bad inverter/charger, CB radio.

I removed all of my fluorescent tube lighting and replaced them with LED strips. I replaced my OE TV antenna booster with a King Controls Jack antenna and booster (I power down the booster when the RV is unattended). I eventually replaced my Xantrex Freedom MSW inverter/charger when it quit working, with a Magnum PSW inverter/charger. My CB radio is a non-issue as it is only used while traveling and even then, rarely.

Another RV tech told me that any battery charger can emit a radio frequency, so he told me to disable my Magnum’s battery charger when it is not needed, which I have.

Unfortunately, NONE of the above measures have solved my problem. I have been dealing with this issue for years.

Someone recommended replacing the Coleman t-stat with a residential, but I have two zones with remote sensors for heating & cooling, so I don’t know if a residential will work.

Any suggestions?

[Gadget_Man]

No worries Doug, thanks for your help.

[dougrainer]

I was just pulling your leg. No insult meant. Doug

PS, YOU said the paint was important and the AC upgrade not doable right now due to the paint cost. That is why I had fun with you.

[Gadget_Man]

Thanks for the reply, even if it was somewhat insulting. Please show me where I said I wouldn't consider a new system. I merely said in other words that I was getting ready for a re-paint, so I would attempt an easy fix first, due to the cost. With or without the cost of a paint job, most people would do the same. To bash someone because they want to attempt the easiest/least expensive fix first just doesn't make sense. Regardless, thank you for your information.

[dougrainer]

Gadget Man wrote:
A very expensive option, but I'm sure that would work. I think I'll give your first suggestion a try first. I'm getting ready to dump a bundle in a new full body paint job, so replacing both A/C's isn't doable right now.

May I ask why you suggested Dometic instead of Coleman?

Sorry, but you will spend THOUSANDS of dollars on a Paint Job, but will not spend $2500 to $3000 on a better upgraded AC system and you ARE concerned about your dog? The Units are original and have outlived their normal service life, so spending money on this is not a large waste. I would help you but I will be spending my money on a around the world Cruise instead of the needed Heart Surgery:B Priority's you understand:B The reason Dometic is simple. The control system is very easy to install and the RVP systems are NOT inexpensive to upgrade too. The Dometic Penguins COME with the needed control boards and the RVP systems do not. Are you positive you are NOT a former customer of mine? Your logic sounds like some of my customers back in the 2000's. Back then FULL paint was about a $10,000 option and when we delivered the new unit, some of our customers would scream bloody murder if we told them that to wire their tow vehicle would cost about $100. They were willing to pay $10,000 for optional paint but would not spend $100 to get their tow vehicle wired:h But, it is your money and you are free to spend it your way. Doug

[Gadget_Man]

A very expensive option, but I'm sure that would work. I think I'll give your first suggestion a try first. I'm getting ready to dump a bundle in a new full body paint job, so replacing both A/C's isn't doable right now.

May I ask why you suggested Dometic instead of Coleman?

[dougrainer]

Another solution. Since your 2 RVP units are 14/15 years old
Replace BOTH roof top units with Dometic 15k Heat Pumps and replace the wall tstat with a 10 button Dometic programmable tstat.
All you have top do besides replacing the roof top units is, Run the Phone type COM cable thru the AC duct from the rear AC/HP to the front AC/HP. THEN, use or make an adapter to install on both ends of the existing tstat wire from the roof to the wall tstat. It is 4 wire phone type modular connector pin. Dometic used to make such an adapter, but they are easy to make. You would have to replace the inside wall temp sensors, but you just clip and splice the existing 2 wire harness with the Dometic sensors. Doug

[Gadget_Man]

Doug,

Thanks for the reply. I made a typo in my OP, I only have 2 A/C units, not 3. I just fixed the typo.
:S

The fix sounds complicated so I will forward it to my mobile RV tech and see if he is willing to attempt it.

Thanks again.

[dougrainer]

Fleetwood back your year wrapped the 120 and tstat wire harness together in the roof. THAT causes the ripple trip for 00. The ONLY true fix is to run a NEW 8 wire tstat wire from the Zone 1 to the wall tstat. Bypassing the 120 wiring as best as possible. Due to the type control system RVP uses, there is no after market tstat control system that will work. The other solution is to replace the control boxes and run a separate tstat wire bundle for the other zones and install regular RVP wall tstats which will be expensive. Doug

PS, since you have 3 AC units, the problem "could" be the com wiring between the Zone 3 and Zone 2 and then going to Zone 1. Those wires could also be wrapped with the 120 wiring. Can you determine if the 00 is isolated to just one zone? Or when the trip happens the complete tstat locks out with the 00?