2018 Berkshire 39a. A/C weirdness

[MobileMFM]

Awesome- really appreciate it!

Originally Posted by rdonihoo

Turned out when the PCS goes out, most times it also takes the hi-lo HVAC. Modules (there are two). Also for safety sake they replaced one of the data cables.
MHSRV worked overtime and tireless to get my coach ready
For a family reunion I needed to attend. The touch screen
And A/C ‘s are all working like new.
Thanks for everyone’s help and advice.

[anaviator]

Originally Posted by MobileMFM

Any chance you can tell me how you swapped the 2 ACs?

Having the same issue- called Danny and he said the problem is the data cable going from back of breaker box to first AC. No communication between the 2.

Thanks!

The comm boxes, at least on my coach, are mounted to the front-inside wall of the AC case. You have to go up on the roof, remove the 4 screws holding the AC case together, and remove the top.

The comm box will have Precision's name on it and will have one or two RJ12 (phone line) connections. The first one in line will connect to the Precision Circuits controller, the other will connect to the next AC in line.

In my case, I swapped the first in line (bedroom) and the last in line (living room), and it resolved my problem. The issue with mine was apparently it's ability to pass signals along as swapping them got all three ACs working again.

[MobileMFM]

I know exactly what you’re talking about and where they are. Yesterday I got on the roof and ran a phone cable from behind breaker box (under bed) into the first unit as HVAC line in and no luck. I did the same with HVAC line in for 2 (kitchen) and 3 (living room) and nothing. Is that what you’re talking about?

Also, before doing so I turned off breakers, did the hook up and turned on breakers followed by HVAC reset on the panel.

Sorry for barrage of requests as I just got the kids to Disney and would hate to cancel the trip on them to take the rig in. 2 freestanding ACs from Home Depot are keeping it cool at 75 inside.

Thanks a million again!

Originally Posted by anaviator

The comm boxes, at least on my coach, are mounted to the front-inside wall of the AC case. You have to go up on the roof, remove the 4 screws holding the AC case together, and remove the top.

The comm box will have Precision's name on it and will have one or two RJ12 (phone line) connections. The first one in line will connect to the Precision Circuits controller, the other will connect to the next AC in line.

In my case, I swapped the first in line (bedroom) and the last in line (living room), and it resolved my problem. The issue with mine was apparently it's ability to pass signals along as swapping them got all three ACs working again.

[Eric B FR Diesel]

Originally Posted by MobileMFM

I know exactly what you’re talking about and where they are. Yesterday I got on the roof and ran a phone cable from behind breaker box (under bed) into the first unit as HVAC line in and no luck. I did the same with HVAC line in for 2 (kitchen) and 3 (living room) and nothing. Is that what you’re talking about?

Also, before doing so I turned off breakers, did the hook up and turned on breakers followed by HVAC reset on the panel.

Sorry for barrage of requests as I just got the kids to Disney and would hate to cancel the trip on them to take the rig in. 2 freestanding ACs from Home Depot are keeping it cool at 75 inside.

Thanks a million again!

Any luck on getting the A/C's fixed?

[MobileMFM]

No. Just found out I needed RJ12 (not RJ11). Ordering on Amazon. Stay tuned

[Eric B FR Diesel]

Originally Posted by MobileMFM

No. Just found out I needed RJ12 (not RJ11). Ordering on Amazon. Stay tuned

That would be correct, the multiplex system with us data cables vs phone cables. sometimes you can find them at a office department store. Usually the two AC are daisy chained together, what floorplan do you have? I can see about trying to get some information. Also you may be able to just re-terminate the ends of the cables you already have, might be a bad contact or might not have the insulator ran all the way up to the connector which usually causes issues in humidity.

[MobileMFM]

It’s a 2020 Berkshire XL 40E
Just ordered the RJ12
Fingers crossed one of these fixes works
Thanks for the help. This forum has been amazing!

[RDupre]

Yesterday my wife and I returned home from a 25 day, 3700 mile trip to Niagara Falls and up the east coast from S. Louisiana. As I posted earlier, we had the same problem with both of our A/C units on our 2020 Berkshire 39A. Danny called me last Monday and showed me how to get to the "HVAC Diagnostics" screen on the display. Module 1 (Rear A/C unit) was not working, and Module 2 had a good reading. But when Module 1 goes out, the other unit cannot get any signal. We had a tech. come out in Mt. Airy, NC and he found the bad Module in 5 min. Danny instructed the tech on how to remove the good module from the front A/C to the rear A/C so we would at least have A/C in the bedroom. Danny shipped me a new module to my next stop in Hilton Head, SC. At first, the electronic control did not work the A/C for this temp fix, but we were able to manually turn on the rear A/C compressor on the HVAC screen. Please note if you do this the compressor does not cycle off. So, I ran the fan on high and every few hours I would shut down the compressor. I also order a second module as a spare. The cost was about $70 including shipping. Once we received the parts from Precision Circuits, i had another tech in SC install both new modules and kept the good one as a spare. Once it's installed you have to shut down power, including the 12v salesman switch to reboot the precision system. The final step is to go back to the HVAC screen, and press the HVAC Reset button. It took a couple of times to reboot both my A/C units.
Danny with Precision is great. May of you recommended that I call him. He saved our vacation. Also, a BIG thanks to all of you on this forum. I have learned a lot from reading posts from all of you. On my first tip with our new coach last Sept, we got locked out of our Precision screen because of some mistake we made. After I posted on this forum, some of you suggested calling Danny. He showed me how to reset the system. When my rear camera was very cloudy, I took a posted recommendation and upgraded the camera. So, Thank You for helping us rookies.

[MobileMFM]

Update:
- went through diagnostics with Dan and determined it was the cable connecting Precision Plex to first AC (bedroom)
- bought RJ12 6P6C 50ft cable on Amazon and connected it from back of Precision Plex (under the bed, middle panel) directly into AC 1 (bedroom) HVAC com in (com out is the daisy to AC 2 in kitchen), turned on breakers, hit HVAC reset and all ACs are now working.
- will take detailed photos later this week to post in case anyone in the future needs steps.
- now gotta figure out how to secure the cable on outside of rig for drive back to Utah
Thank you all!

[Eric B FR Diesel]

Originally Posted by MobileMFM

Update:
- went through diagnostics with Dan and determined it was the cable connecting Precision Plex to first AC (bedroom)
- bought RJ12 6P6C 50ft cable on Amazon and connected it from back of Precision Plex (under the bed, middle panel) directly into AC 1 (bedroom) HVAC com in (com out is the daisy to AC 2 in kitchen), turned on breakers, hit HVAC reset and all ACs are now working.
- will take detailed photos later this week to post in case anyone in the future needs steps.
- now gotta figure out how to secure the cable on outside of rig for drive back to Utah
Thank you all!

Good to hear you got it working.

[rdonihoo]

Folks, since I started this topic, I feel it necessary to relay all the info I learned during my AC problems.
First. Symptoms were No control of AC units at precision circuits touch screen. (2018 39a). The PCS control board was replaced, partial control was regained but still not working correctly, contacted tech support and told to replace both hi-lo HVAC modules (there are 2). And the data cable , not sure which one but it ran from the front unit to the back of the coach, it was visibly burnt and a feed thru connection. The tech thought maybe this stated the whole domino effect, causing the PCS board to fail and take out the HVAC modules. Hard to say which came first or what caused the failure in the first place. If this happens to you ,
Replace PCS board and both HVAC modules and data cables if possible, FYI: data cables are not phone line cables, they are cat10 or something close, contact Precision Plex for cable details, also all pc boards are on their web site, hope this helps someone.

[Eric B FR Diesel]

Originally Posted by rdonihoo

Folks, since I started this topic, I feel it necessary to relay all the info I learned during my AC problems.
First. Symptoms were No control of AC units at precision circuits touch screen. (2018 39a). The PCS control board was replaced, partial control was regained but still not working correctly, contacted tech support and told to replace both hi-lo HVAC modules (there are 2). And the data cable , not sure which one but it ran from the front unit to the back of the coach, it was visibly burnt and a feed thru connection. The tech thought maybe this stated the whole domino effect, causing the PCS board to fail and take out the HVAC modules. Hard to say which came first or what caused the failure in the first place. If this happens to you ,
Replace PCS board and both HVAC modules and data cables if possible, FYI: data cables are not phone line cables, they are cat10 or something close, contact Precision Plex for cable details, also all pc boards are on their web site, hope this helps someone.

Thank You for sharing, and updating on what yours took to get fixed. recently we have had a lot of people reach out and say that they appreciate the forums and how we are trying to help. the more shared knowledge the better.