A/C & Thermostats

[Chickadee]

O.K, Newmar Gurus: ....have 08, 4502 Essex w. 3 A/C units (lvrm, kit, bdrm). ALSO, located inside the coach are 3 ea., 1.5 inch or 2 inch diam., white, dome/grill caps covering what are (I think) temperature sensors. One such sensor is located on the aft face of the lambriquin to what would be the right of a fwd. facing co-pilot seat (I surmise to monitor temp in livng. rm. area)...a 2nd sensor is located on TOP of a fabric covered valence around the rear facing window in the street side slide (we guess it's to monitor kit. area temps).....and, a 3rd sensor is presumably to monitor bdrm. temp. is located on wall facing inboard between aft edge of slideout bed and aft closets.

Ques:

1. Are these sensors "thermistors?"
2. Is ea. respective sensor connected ONLY to sep. A/C roof units (ie., lvrm. sensor to fwd. most A/C, kit. sensor to mid. roof A/C unit, and bdrm. sensor to aftmost roof top A/C unit)?
3. If one area sensor reads high temp when that area is without a doubt much cooler, is there an adjustment that can be made or must sensor (thermistor) be replaced??

Thanks

[Jetsmania]

Hi Steve! I will try to answer your questions:


#1 Are these sensors "thermistors?" Yes.

#2 Is ea. respective sensor connected ONLY to sep. A/C roof units (ie., lvrm. sensor to fwd. most A/C, kit. sensor to mid. roof A/C unit, and bdrm. sensor to aftmost roof top A/C unit)? Yes

#3 If one area sensor reads high temp when that area is without a doubt much cooler, is there an adjustment that can be made or must sensor (thermistor) be replaced??
Now the fun begins. They cannot be adjusted. Newmar allows a tolerence of about 3 or 4 degrees. They are a pain in the butt. Sometimes Newmar will change the location because of false reading caused by Sun, etc. I have had plenty of bad luck trying to get our middle sensor to read close to anything. It has been moved and changed, and is still off about 5 or 6 degrees. Paul

["007"]

If the thermister was installed in inlet or outlet port of AC maybe there would be better control. PORT CONTROL device , I wonder if anyone ever moved their thermister near the port of AC to see if it would work better.????

[soricobob]

Our zone 1 temp sensor would "go crazy" for a couple of years. It actually went up to 150+ degrees (and back to normal) within a minute or two. "They" reprogrammed the panel a few times, but it wasn't until we were at a rally, and the tech actually saw what was going on that the sensor was replaced.

[ET]

I used my Reytek Infrared Temperature Gun to determine what temperatures actually are throughout the coach as well as what each sensor shows for temperature against what the thermostat shows it should be. I only have two 15,000 AC/Heat Pump units and 1 external sensor. The other sensor is actually in the thermostat. I’ve found that both are within 2 degrees of each other. The bedroom temperature varies considerably throughout such as near the widows, entrance, ceiling etc. So if I wanted my bedroom temperature to be 74 at night over my mattress and it currently shows 76 when the thermostate reads 74, I’ll lower the Zone to 72 to compensate and the mattress area will read 74.

[Chickadee]

Thanks all !! I think our kitchen (mid coach) thermistor/sensor (now mounted on window valence) is out of whack....or....must be relocated. If it needs to be relocated, I'm in trouble, since I wouldn't know how to begin following wiring and relocating it elsewhere behind panels etc. Guess I'll check w. techs in Nappanee on next visit. Thanks again. Steve

[Jetsmania]

Hi Steve! If it needs to be changed, the E-Plex needs to be reset. Not hard to do. If they relocate it for you, they usually leave the cover for the old one in place so you do not have a hole. Paul

[RVDude]

chick here's some more specifics for you. The following applies to the 07 EX (substitute AquaHot where I say "oasis" and delete "probably"). It might translate directly to chick's 08 if it's not a rear bath model..

ePlex zone 1 = forward most white dome, forward roof unit, dash+kit furnace heat exchangers, probably oasis pump 1, oasis zone 1

ePlex zone 2 = kitchen white dome (have Newmar move that from the top to the side of the lambrequin as it'll always read hot where it is - do it under warranty and they can typically rotate the top panel to make the hole disappear also note the wire slack is short there), mid roof unit, NO furnace exchangers, no oasis pump

ePlex zone 3 = white dome perhaps underneath you bath med cabinet/above the sink, NO roof unit (there is a dometic hvac controller only unit probably mounted in your bath vanity that acts as the "phantom" roof unit controller), furnace exchangers in the bath/toilet area, probably oasis pump 2, oasis zone 2

ePlex zone 4 = white dome in bed (probably back wall), rear roof unit, bed furnace heat exchanger, probably oasis pump 2, oasis zone 3

basement heat = (I know 08 have a slightly different fixed temp setup here) but it might have a mechanical bulb (07) or other setup in the water bay (probably lower right back corner), no roof unit, no ePlex control (may be different on 08), probably oasis pump 3, oasis zone 4

oasis stir pump = no oasis zone, probably oasis pump 4

engine preheat (if installed) = no temp senders, probably oasis pump and oasis zone "engine preheat"

The white domes can be replaced with tan domes at Newmar

Now, regarding the "thermistors" which are sort of thermistors and a programmable controller. They are ePlex temperature controllers which measure the temp and convert that temp in a timed string of electrical pulses. You’ll find a little tab inside the dome (the actual thermistor) on a flat wire pigtail about 18in long ending at a black ePlex controller which has a red LED and a cat 5 type networking wire coming off that. The main ePlex "brain" (behind the forward display control which Newmar will call it the "clock" as it "clocks" the pulses to determine what data has been sent) reads those pulses and determines what to do. YES YOU CAN change the "temperature to count" conversion table those devices use. Newmar can print what exists and program whatever you want from their laptop. Yes the tables might be off OR most likely your white domes are mounted in bad places giving elevated/lowered readings – Newmar loves to mount them in bad places. The kitchen dome mounted on top will typically read very high - because it is in a high temp spot due to sun out side or the natural hot pocket of air there. The bedroom might read very low as it might be mounted next to the cold outside wall. Newmar will move those for you if that is the problem. Note the kitchen one they can turn the top panel around to hide the hole.

Another common but often undetected problem is the ePlex temp senders may not be programmed to read low temps (essentially reading no lower than maybe 55-60 degrees). Newmar can program the "temp to counts" tables with the lower temps and counts. This could be a problem if you intend to store the coach and use the ePlex to hold a 40-45 temp. If these completed count tables are not in place, the ePlex will just not know any temp below the lower table limit and thus not turn on the heat.

A final undetected problem is the external ePlex temp sender (typically someplace on the door side of the generator slide opening hanging among all the Evans control wiring and above the HWH controller there) is that its table may not be programmed to read much below 20-30 degrees. Have Newmar check that out if you run the coach in cold places.

If an ePlex controller needs replacing the new part's new network address needs to programmed into the ePlex. The ePlex is actually a miniature computer network where all the devices/controllers are network addressable so the brain (Newmar calls this the "clock") has to be reprogrammed with the new addresses.

PM me and we can talk on the phone if all this doesn’t make sense. It can get really tricky as to what does what and how on these ePlex systems.

[RVDude]

One other thought on the bsmt heat - particularly on the 07 EX.

The bsmt heat is completely independent of the ePlex. It's own mechanical thermostat is in the water bay and regardless of how your ePlex is set or even if "all zones off" the bsmt heat will still come on if needed IF the AH is hot enough (i.e. the "low temp cutout" LED on the AH control panel is lit). The bsmt heat shares AH pump #2 (along with ePlex zones 3 and 4 all on the same serial plumbing string) and the cozy exchanger fan is signalled as AH zone 4.

Don't ya' just love this stuff?????

[Chickadee]

WOW!, RVDude: Ya REALLY know some stuff......thanks. I'll need to study your post carefully (probably for a few weeks) to make sure I understand it all.....but....Thanks again. Steve

["007"]

Its a good thing we have RV Dude and others that know all the toys in these HIGHLINE coachs and what makes them tick.
I'll just stick with my low end coach at this late date in life.
It may be low end but its still a NEWMAR.

[Jetsmania]

Hi Jeff! Great stuff! Just a few notes, Newmar now has a few more colors for the domes. When we changed a sensor last week, we only had to do a reset for the E-Plex to read it. The sensor is still off 5 or 6 degrees. There is no way it is the temp at the sensor that it is reading. I can't believe we have a second bad one. This sensor was also relocated at our last trip to the factory. Any ideas?? Paul

[RVDude]

jets - it figures that the ePlex can read the new device's address by a "reboot". Makes sense, thanks for that update. More colors too! Yipee!

Regarding the delta temp. First, I take it you are sure that you are measuring the dome temp with another accurate thermo... Temps can vary wildly by just moving a few inches due to hot/cold walls, airflows, etc.

Given the delta temp have Newmar reprogram the count table for that sender. Jason knows exactly what to do.... The count table looks something like the following (the values below are purely illustrative).

temp count
30 100
35 120
40 140
...
70 200
75 220
....
100 300

All they need to do is shift the values by the delta degrees and you'll be in business...

Note in the table above there would be no reading below 30 degrees or above 100 degrees, so if you need that make sure they program values down as low/high as you need.

[RVDude]

double oh or seven & seven - Every Newmar has highline owners, and it's the owners that makes the community here! Besides, you are lucky to have skillfully navigated avoiding the highline headaches those hightech coaches can deliver! Life is too short - KISS!