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Topic: AC Breakers (Read 980 times) previous topic - next topic

Re: AC Breakers

Reply #25 –
Peter,

If the breakers for the A/C units are off at the foot of the bed you can leave the shore power alone. If you unplug shore power it is just like belt and suspenders so if it makes you more at ease unplug. Yes removing a wire off breaker 52 will kill the 12VDC to the A/C system.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AC Breakers

Reply #26 –
Absolutely frustrated.
Unplugged the 15 amp shore power...disconnected 12volt at passenger dash ( was tied with step cover)...turned off both ac breaker at foot of bed.

Then went on roof and installed the new circuit boards for both AC unit which came with the 5 button thermostat as a complete upgrade kit.  This part did not go too bad
Then went into coach and started the generator ( I only have 15 amp shore power and wanted to fire up both AC's if possible )
I then re connected the 12 volt power and put both AC 120 breakers back on
I then plugged in the 5 button thermostat and went through the initial reset required.
NOTHING....no power to the thermostat at all. I unplugged the thermostat and replugged it..nothing
Frustrated I went on the roof and noticed the front AC fuse had blown. Tried to replace it and it kept blowing. Went down and disconnected the 12v power and replaced the fuse. It held. Then I connected the 12 volt power and it blew again!!
Don't have a clue....  Any idea why the fuse keeps blowing when the 12 volt is connected???  I am sure the  circuit boards were done correctly and the  data cables were put back to the same configuration as I stated at the beginning of the post ( see pics)
Idea????  Help!!!
PS. I even unplugged the thermostat at at the wall and the fuse blew when I connected 12 volt....I have not changed any wiring at all to cause a short!

I know this blurb is long, but I will ask something else. Put the dip switches on circuit boards to: front  ac.  heat strip on furnace on.
Rear ac.  Zone 2 on. Furnace on.  Are these settings correct??
Just phoned Dometic....what a waste of time....
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: AC Breakers

Reply #27 –
Quote from: dicksop –
I went on the roof and noticed the front AC fuse had blown. Tried to replace it and it kept blowing. Went down and disconnected the 12v power and replaced the fuse. It held. Then I connected the 12 volt power and it blew again!!

Peter,

You have a direct short to ground.  Sure sounds like you either have a broken wire in the communication cable or a bad connector shorting to ground.  When you take the 12vdc away and the fuse holds there is no flow of electricity so the fuse holds.  When you reconnect the 12vdc the electricity starts to flow (amps) and with a direct short it will be more amps than the fuse is rated. The hard thing is finding the short and fixing, this may also correct the intermittent loss of power to Tstat that you have been having.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AC Breakers

Reply #28 –
Ok so if I substitute the data cable from the wall thermostat with  another run through the coach to the front AC will that be an indicator?
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: AC Breakers

Reply #29 –
Peter,
The short answer is Yes. That is how I would troubleshoot a bad cable.
Now you need to be sure that the wires in the plugs are the same as the OEM ones as sometimes they are different depending on the application. Wire could be set up like wire 1, 2, 3, 4 goes to 1, 2, 3, 4 on the other end, Or does the wires swap to 1, 3, 2, 4 on the other end?

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AC Breakers

Reply #30 –
I sure hope  turboj will chime in on this as he has a lot better ability to explain what I am trying to convey on the wiring of the communication cable ends.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AC Breakers

Reply #31 –
So correct me if I am wrong but the power  to the front AC comes from the data cable that is connected to the thermostat and runs to the front AC right?  So if the front AC fuse keeps blowing it HAS to be that cable right? 
Unfortunately I am spent for the day and won't be able to check/diagnose anything till tomorrow, but ANY help will be appreciated ( and maybe save me tons of dollars)
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: AC Breakers

Reply #32 –
The 12 volts in the front A/C does not come from the data cable. 12 volts from the front A/C powers the thermostat.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: AC Breakers

Reply #33 –
The front AC board has 12 v going to it from the coach.  This 12 volts powers from the coach is what powers the board and  the thermostat as craneman said above.  The 12 volt power from the front control board  powers the rear AC circuit board via the phone wire.  You could have both breakers turned off at the bed for the AC's and the thermostat would still have power to it since it is coming form the coach 12 volt system. 

Go to page 27 and it shows you how it is wired up.
http://myrvworks.com/wp-content/uploads/2019/04/Duo-Therm-4-Button-CCC-Diagnostics-Service-Manual.pdf

Disconnect both data cables.  Reinstall fuse.  repower up with 12 volts.  Does fuse hold or blow?  If it did not blow try plugging in 1 data cable at a time to see if fuse blows.  If it blows while attaching one of the data cables the problem could be the data cable has short.

Look at the data cable receptacles (not the data cable, ends on board or thermostat).  Check and make sure the little pins did not get crossed and is touching one of the other pins. 
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: AC Breakers

Reply #34 –
Turbojack
I will give your suggestion a shot tomorrow. This cat and mouse game is certainly mildly entertaining but definitely frustrating!!
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: AC Breakers

Reply #35 –
Quote from: turbojack –
Look at the data cable receptacles (not the data cable, ends on board or thermostat).  Check and make sure the little pins did not get crossed and is touching one of the other pins. 

Need to look on the board and also the couplings to make sure a pin is not misaligned and are crossed..

Home Depot has a RJ11 tester where you can test your cables to make sure they are good

http://www.homedepot.com/p/Klein-Tools-LAN-Explorer-Data-Cable-Tester-with-Remote-VDV526-100/309925931?source=shoppingads&locale=en-US&&mtc=Shopping-RM-F_DYNM-G-D27-027_011_TOOLS_ACC-KLEIN_TOOLS-NA-NA-SMART-NA-RMP-MK495473330_9016864402_FY22_1927_RM2&cm_mmc=Shopping-RM-F_DYNM-G-D27-027_011_TOOLS_ACC-KLEIN_TOOLS-NA-NA-SMART-NA-RMP-MK495473330_9016864402_FY22_1927_RM2-71700000083602792-58700007073070013-92700063677501837&gclid=Cj0KCQjwpImTBhCmARIsAKr58czrOddIVjR-RFXClTpxrPpUU0TFKKg3iRweQL4H129F7thVAFhOfKkaAitAEALw_wcB&gclsrc=aw.ds

If you get the tester you could test the cable from the circuit board all the way to the thermostat or from circuit board to circuit board.  That way you would also be testing the couplings to make sure that is not your problem.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: AC Breakers

Reply #36 –
So I have an update

I installed the 5 button thermostat and the 2 new circuit boards
As I said before that resulted in fuses blowing on the front AC unit. I followed what was suggested (including buying the meter to check cables) I did check some cables and got some continuity between some and re booted the thermostat and it came on. My dip switches are set in the Ac units as follows:
Ac 1. Heat strip. On.  Furnace on.  All other switches off
AC 2. Heat strip on. Furnace on. Zone 2 on. All other switches off

I got the front AC on ( exactly how I started this topic and the new thermostat shows zone 1 now but NO zone 2. Front AC and furnace etc works but no rear AC. I checked fuse in rear AC. It was good. New circuit board was wired correctly. Cables look ok.
Frustrated again!!
Is the rear circuit board dip switches correct??  Any suggestions why the 5 button won't recognize zone 2 or power up the AC??
Suggestions??? Pic one. Front ac
Pic 2 rear ac
Pic 3.  Thermostat
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: AC Breakers

Reply #37 –
Zone one circuit board
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: AC Breakers

Reply #38 –
Also look at the tiny 4 springs in the black jacks. If any are bent or out of their dividers, that would allow for very poor connections.
Jim

2002 U420 42'
Jim Frerichs
2002 U320 42'

Re: AC Breakers

Reply #39 –
Do you have heat strips? If not then that should be turned off.  # 2 zone switch should be turned on and furnace on. It is a communication problem between the front ac and the rear ac take a data cable direct from the front to the rear bypassing the cable in the roof and then reboot the thermostat not the correct term but it is to let the thermostat reset and recognize both ac's. I am pretty sure it is in the communication.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins