Jim McGarvie

9 hours ago, Dr4Film said:

What is confusing is controlling the AC's with a residential thermostat. It appears that Jim is possible an isolated case where he is using one to control his AC's and we ALL know that the Dometic Penguin AC's come with four wire RJ-11 connectors to connect the AC's to the normal Dometic thermostats.

We still don't know how those four wires are connected to his thermostat unless they are using some sort of adapter that goes from a four wire RJ-11 plug to residential wiring. There would have to be two wires for the 12 VDC + & - and two more wires to turn the AC's on/off.

Jim,

Here is the manual for the Honeywell RTH7600D. Possibly it may help resolve your problem.

https://honeywellstore.com/store/images/pdf/rth7600d-7-day-programmable-touch-screen-thermostat-installation-manual.pdf

Thanks, Richard. I already have that manual.

You may all know that the Dometic Penguin AC's come with four wire RJ-11 connectors to connect the AC's to the normal Dometic thermostats, but our Dometic AC doesn't know that. It did NOT come with four-wire RJ-11 connectors, but with a cable containing six conductors. There is no adapter.

I know you guys are all very knowledgeable and experienced. The only thing I can think of to explain this apparent contradiction is that maybe our AC is NOT a 600315.321. I was relying upon the parts list that came with the coach from the factory. Maybe it is some other Dometic DuoTherm?

I have attached a picture showing the baseplate of the Honeywell thermostat showing the wiring connections. Only four of the six wires are used; the other two are taped and stuffed back into the wall.

12 hours ago, Dr4Film said:

Jim,

Here is a link to your specific AC, its installation and wiring diagrams. Possibly this may help you.

https://www.manualslib.com/manual/799601/Dometic-57908-321.html#product-600315.321

I along with others are somewhat confused as to how your thermostat is wired seeing that normally these AC's are controlled with a 5 Button Thermostat.

Maybe a photo or two would help clear up the confusion.

Thanks for the link, Richard. That should be helpful.

I can't speak for "normally", but I can tell you unequivocally that when we picked up this 2002 coach at the Monaco factory in August of 2001, it had a thermostat with no buttons whatsoever. I threw it away when it died a couple of years ago so I can't send a picture of it, but I have attached one of the bedroom A/C thermostat. The original front thermostat was identical but for a switch for heat for the furnace. Nary a button in sight.

12 hours ago, Dr4Film said:

I along with others are somewhat confused as to how your thermostat is wired seeing that normally these AC's are controlled with a 5 Button Thermostat.

Maybe a photo or two would help clear up the confusion.

For those of you who have asked how I wired this thermostat, I have attached a diagram I found somewhere online. I think it is pretty clear, and worked fine. The only way in which I varied from this is I did not add a switch for hi fan. I just wired it to always use hi fan.

8 hours ago, Ray Davis said:

Richard,  Apparently he is using the programing feature,  at least for heat.   I still wonder what thermostat he is using.

The thermostat is a Honeywell RTH7600D. I use it for both heating and cooling, but I only use the programming feature for heating. I'm sure it would work fine for cooling as well, just haven't found the need.

12 hours ago, Ray Davis said:

It's non programable but this could probably be made to work.    https://www.homedepot.com/p/Economy-Non-Programmable-Thermostat-with-1H-1C-Single-Stage-Heating-and-Cooling-CT31A/100400017

Thanks for the input, Ray. But I guess since you are recommending I replace my thermostat you must be assuming there is something wrong with our current one. Can I ask what makes you think that? Because I really don't want to lose the programming capability if I can help it. I don't use it for cooling, but for heating it follows a schedule keeping the interior at 72 degrees until 9 pm, then letting it drop to 55 (which it very seldom does) until about 1/2 hour before I usually get up in the morning, then warming it back up to 72 by the time I get up.

I don't have a reason to believe there is some reason a programmable residential thermostat shouldn't work properly with our particular A/C, primarily because it worked perfectly for two years.

What am I missing?

15 hours ago, Ivan K said:

I think they make them run off backup batteries,  Jim would probably know best.

Thanks for your confidence in me, but I'm not sure I know how it works. I think the batteries in the thermostat are primarily for display and memory. The thermostat it is replacing is really only a switch, right?

18 hours ago, vito.a said:

I have not seen anyone successfully use a residential thermostat on a Dometic RV A/C.  I'm just saying I've not seen one work.

The Dometic thermostats and A/C units use 12v DC signals sent through an RJ11 phone cord to control the A/C.  There are even three different versions of the Dometic A/C control input/output.  

Early 4-button thermostat through about 2002 (these thermostats were very unreliable)

5 button Comfort Control thermostat from 2003 until a few years ago.  

The current CCC2 (Comfort Control Center 2) programmable thermostats.  

The Dometic thermostat must be the same generation as the A/C system, or use a conversion control board.   

I would first call Dometic with your A/C model and serial number and determine what version it is.  Then install the appropriate thermostat.  You will need to program the new thermostat to the A/C.  Switch the bottom thermostat black slide switch off.  Depress both the top and bottom program buttons simultaneously and slide the on/off switch on.  You will see FF in the display.  

Your other alternative is to replace both the A/C and the thermostat with new ones.  

Best of luck!

Thanks for the reply, Vito, but our 2002 (made in 2001) coach never had any buttons. It was a really old fashioned thermostat, just a couple of switches and a rheostat. Our residential thermostat worked perfectly, for the furnace and for the A/C, for two years.

Our front roof A/C is a Dometic 600315.321. Intermittently (don't we all hate that word?) the compressor will come on without the fan. I can switch the fan from Auto to On on the thermostat and solve the problem temporarily. Or I can turn off the circuit breaker for the front A/C or remove the thermostat from the wall plate, either of which, of course, stops the compressor and the fan. Sometimes when it is acting up I will remove the thermostat for a while, and when I plug it back in the A/C comes on normally.

The thermostat is a residential programmable Honeywell. When this same issue occurred last month my troubleshooting led me to believe the problem was in the thermostat, so I replaced it with a new one of the identical model. That seemed to have solved the problem for a while, then yesterday it returned to its previous behavior.

Any and all suggestions welcome.

Thanks.

Jim

8 minutes ago, DavidL said:

You would contact Cummins company with your VIN  / engine serial number and ask them.  Yours (like mine) is too close to the transition from one to the other.

If 9 pin, likely J1939.  But mine is 9 pin and is J1708 (older protocol).

From Cummins:

"There was a gradual shift from J1708 to J1939 between 2004 and 2007. Any engines prior to 2004 are most likely to be exclusively J1708. Engines from 2004 – 2007 are likely to have both protocols available. After 2007 it’s most likely going to be J1939 (with the odd exception). The ISX has been around for some time, so check the engine manufacture date to get a better idea of the communication protocol, rather than the engine model."

Thanks David.

On 9/2/2021 at 8:58 AM, DavidL said:

a 9 Pin Deutsch connector IS OBD.  It is NOT OBDII.

9 Pin is typically J1939 protocol (it may also have J1708).

OBD is On Board Diagnostics.  Many different generations / types.

OBDII is one particular flavor (US Gas vehicles)

On Most J1939 vehicles, the round connector is also at the base of the steering column.  but look around within a foot of the column.

You may be able to use the one at the back, but bluetooth does not have very long range so it is unlikely it will reach up front.  Not aware of a bluetooth "repeater" either.

When I get around to it, I will have a solution for the issue, but it will be much more comprehensive than what you are asking for.

Thanks for the clarification, David. I should have realized the Deutsch connector at the rear of the coach was a type of OBD. How does one go about determining whether a port is J1939 or J1708?

1 hour ago, DavidL said:

You would need to confirm if your Cummins has OBD (note:  Not OBDII).  I would think a 2002 does.  It should be a round Deutsch connector near the steering column, possibly at the base.  Then you would have to confirm what communications protocol it supports as your year (same as my Newmar's year) is about when things switched from J1708 to J1939.  Once knowing that, then look at Bluefire bluetooth adapters.

I'm fairly confident our coach does not have OBD. The only diagnostics port I'm aware of is the only one mentioned in manual for our coach: the round 9-pin (J1939) port with the word "ENGINE" at the rear below the oil dipstick. I have spent way too many hours under the dashboard, and have never found a port there. I would love to be proved wrong, but....

Or is it possible to plug a Bluetooth adapter into that for a scan tool up front?

9 hours ago, DavidL said:

You might get a scan tool and view odometer via your phone / tablet.

Thanks, David, that's a good thought. Any particular recommendations? Any recommendations? How do they interface with the vehicle? Our Cummins ISB 5.9 has no OBD port.

Just now, monacowner said:

Hi Jim! I have the same problem. I just take a picture of it with my phone and then stretch it out to make it bigger / more clear.

Ha! I do that too! But not while I'm driving. I often check the trip meter, which I reset when I fill the tank, to get a feel for how much further we can go before refueling.

This has been an issue since we brought the coach home from the factory 20 years ago. It probably hasn't gotten worse, but my eyesight has. Has anyone experienced this problem and found a solution? Can't make it any larger, but a stronger backlight might help.

Thanks.

Jim

2 minutes ago, waterskier_1 said:

We had a similar discussion regarding this on another forum.  We concluded that coaches with Air Ride only (no Air Leveling), must dump everything (both air tanks) to drop the coach.  Coaches with Air Leveling (specifically HWH and maybe Power Gear) do NOT need to dump the air tanks to drop the coach.  On those systems with air leveling there are 6-pack valves (solenoids) that control routing of the air to the air bags.  When Air Level dump valve is energized only the air level valves are operational, and the ride height valves are inhibited.  Therefore, the main air tanks are disconnected from the air bags when the coach ignition is OFF.  Now if you start the engine, the coach will begin to rise as the ride height valves become energized again.  I think, but have not tested a Power Gear system to confirm it operates the same.  As previously stated, if you don't have Air Level, you don't have the 6-pack valves to isolate the ride height valves, and the main air tanks, so you have to dump everything.

Most people choose to dump before leveling to get the coach as low to the ground as possible.  It's not required because if the coach can't be leveled by adding air to the low side, the system will dump air as necessary (within it's design limits).  

I think anyone who stores their coach, and doesn't have leveling enabled (with power for the compressor), or on hydraulic jacks, the coach is going to settle all the way down eventually.

Spot on, Rick. Our coach does not have air leveling, and deflating the air bags deflates the entire system, tank and all. And as you point out in your last sentence, within a couple of days our bags are fully deflated no matter what we do.

1 hour ago, Dr4Film said:

Jim,

When I first get home all I have to do is dump the air bags to back in. Then over time the air tanks will lose all of the air until they register 0 psi on the gauge.

However, when I need to pull the coach out from under the house, I first start the engine to build up the air pressure to release the rear brake springs, then put the coach in gear and hold down the Dump Air Switch until I am completely out from under the house.

Even though your coach doesn't have Air Leveling you must have a switch which dumps the air from the bags, correct? Or does your Air Dump Switch dump ALL air from the air tanks & the bags at the same time? If so I wonder if you could alter the air system so you could just dump air from the bags separately?

Having a Knight you most likely only have four air bags to deal with.

Richard,

Nope, no switch to dump just the bags, only the entire system, bags and tank. I would love to be able to just dump the bags. And yes, we have four bags.

12 minutes ago, Dr4Film said:

I simply use the Dump Switch on the HWH Control Panel. I have to hold my finger down on the switch while backing up otherwise the coach wants to return to Ride Height. One I get backed into position and shut the engine down, I leave the HWH Leveling Control in manual in case someone starts the engine. I also made up a laminated sign warning anyone who may have to move the coach with instructions on how to do it without destroying the ceiling of the RV Port plus the AC's on the roof of the coach.

I don't have to fan the brakes to reduce the air in the front & rear tanks as they are two separate systems.

My system is different: I don't have air bag leveling, but I have to hold the Air Dump switch on the dash as I am going in and out, and eventually the air parking brake sets itself. So I release the air switch until I can release the parking brake and proceed further. Lather, rinse, repeat. But I am quick enough now I can usually drive in or out on one cycle of the procedure.

1 hour ago, Dr4Film said:

The RV Port under our house is exactly 12 foot high so in order to get the coach low enough I have to dump all air or close to it in order to back the coach into its winter home.

Our hangar ceiling is also exactly 12' high and I have to do the same thing. I am waiting for the day I forget!

I wish I could figure out a way to dump just the bags (I have to empty the tank too) and turn off the air to the bags. It could probably be done but the plumbing is complicated (to this geezer, anyway).

2 hours ago, Dr4Film said:

Use the thermostat to turn off the AC not the circuit breaker.

Thanks, Richard, but that doesn't work. The fan would stop, but not the compressor. That's why I suspect a stuck relay on the A/C control board. Since I suspect it is not good for the compressor to run without the fan, I resort to tripping the breaker. When we want to run the A/C I turn the circuit breaker back on (which starts the compressor) and then use the thermostat to turn on the fan.

Disregard. Problem solved. I found a post on IRV2 which said all circuit breakers must be on for the EMS panel to function normally. I had turned off the circuit breaker for the front A/C because it is running continuously (another issue; stuck relay maybe?). I turned that breaker back on and the EMS panel is now indicating correctly.

We have an Intellitec 50 AMP Smart Energy Management System (EMS) Model 750. We are currently plugged into a good (verified by Progressive PT50C)  30A receptacle. At one point our EMS indicated a 50A source rather than 30. I started the generator and the panel correctly indicated "GEN SET", but when I killed the gennie it went back to indicating 50A.

I was able to reset it by killing all power (AC and DC), waiting a bit, then re-establishing power. It indicated normally for a day or so, then went back to the 50A indication. I tried the reset procedure again, twice, but this time it didn't help.

So my questions are, what causes this malfunction, and how can I fix it? Do I need a new control board?

Thanks.

Jim

Thanks to those that responded. I have to admit, though, that even as a fairly capable DIY mechanic the job sounds a bit more daunting than I expected. I.e., I did not anticipate the need to remove the radiator etc. I think this is beyond my desire, if not my skill set, and we don't have time before our next trip to have it accomplished.

I do agree, though, with the suggested work while the radiator is removed. But for this trip I will just carry a new pump, tensioner and belt, JIC. The leak is so small at this point there is no coolant on the floor.

My mechanic was trouble-shooting something else and noticed coolant leaking from the water pump weep hole. I think that means I need to replace the pump pretty soon, before the leak reaches the pump bearing.

Is this the same pump as on the Dodge pickup with that engine? And how big a job is it to replace in the motorhome application?

Thanks.

Jim

3 hours ago, Chuck B said:

Never heard of a Hughes Autoformer protecting a coach from a open neutral.  Chuck B 2004 Windsor

That is one reason I also have the Progressive EMS.

2 hours ago, Chuck B said:

If Bill D were alive today, he would recommend you donate your Hughes Autoformer to the local yacht club to be used as a boat anchor. 

Hi Chuck, I'm curious about Bill's recommendation. We have both the Hughes Autoformer and the Progressive portable EMS. I installed the Hughes first, after a brown-out in an RV park cost us a TV. But I think the capabilities of the EMS are more important.

I've been using mouse milk for years on the Pacbrake. I use it because we use it on turbocharger wastegates for airplanes, and those get pretty warm too. But I'm a big fan of Tri-Flow so might switch to that.