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Old 08-11-2012, 05:45 PM   #1
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Strange electrical issues

Two weeks ago we camped in our 2012 Rockwood 8281ss and everything was working fine. Last weekend the TV, microwave and 12 volt converter charger were dead. Then I found out that the AC won't work without 12 power which we lost. Had to keep connecting to the truck to survive the 94 degree Florida heat. Got the unit back and called the dealer and they immediately went on the defensive over the phone saying that it sounds like a power surge or lightening strike and would not be covered under warranty. They also initially said they couldn't see the unit for a month, causing us to cancel our scheduled vacation this week.

Well I went to the dealership and told the service manager I have never heard of a lightening strike taking out selective devices, usually it takes out everything. Complained to the top and they will see the unit this Thursday. I also told them I have a surge suppressor i use between the power pedestal and the trailer. My theory is that the 12 volt charger/converter had a malfunction and impacted some nearby circuits.

My question is has anyone experienced a similar failure and if so what caused it? Or does anyone have a different scenario that could explain my problem.
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Old 08-12-2012, 07:33 AM   #2
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The air conditioner won't work without 12VDC? Where did you hear that?
The thermostats power comes from the air conditioner; not the converter.

The AC issues may also be a popped GFCI on a wall outlet. Check them all carefully. The Converter is also powered off a circuit breaker on your power panel. Turn them all OFF; then back on.

Let me know what you find out.
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Old 08-14-2012, 10:22 PM   #3
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Lou, I can also say for certain that my A/C will NOT work without 12VDC. I found this out by accident when I had my converter mistakenly powered down with all other 110VAC breakers on. Left the radio on all night, and whattaya know, the A/C quit working at the same time as the radio. When I restored power to the converter, everything came back to life. Not sure what, but SOMETHING in that white box on the roof is 12V!

TV and microwave, that sounds a little different since they are obviously 110.

Hopefully the dealer you are going to has a tech with some solid electrical knowledge. I sure struck out with mine (you can read the saga on one of my older threads).

I would suggest testing voltage on the circuits that power those items that are not working. Trying to diagnose without testing each circuit individually amounts to a good guess.
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Old 08-14-2012, 10:28 PM   #4
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Thermostat is 12v . I'd say a/c would not work.
No signal from thermostat.

Take your cover off there's a plus and a minus and it's not 110.
Actually it says 7.5

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Old 08-15-2012, 07:31 AM   #5
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The thermostat gets its 12 vdc signal from a transformer in the air conditioner's control board; same as your house. Last I looked, my "dumb" house thermostat does not have a battery to run my air conditioner.

Not talking about smart ones that may have a AA or AAA battery inside the thermostat.

http://www.rvcomfort.com/pdf_documents/1976128.pdf

Only 110 VAC goes to the air conditioner and air handler unit (unless you have some kind of 12VDC air conditioner that runs off your battery without any 120VAC. Stranger things have happened).
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Old 08-15-2012, 08:10 AM   #6
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Now you got me thinking.
So in theory the 110 coming into a/c unit also supplies transformer to make 12v for thermostat.
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Old 08-15-2012, 08:16 AM   #7
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Originally Posted by f1100turbo View Post
Now you got me thinking.
So in theory the 110 coming into a/c unit also supplies transformer to make 12v for thermostat.
Yep, now you are thinking.
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Old 08-15-2012, 08:29 AM   #8
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Originally Posted by herk7769

Yep, now you are thinking.
Learning from the best !
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Old 08-15-2012, 08:51 AM   #9
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I learn as well. As I researched this, I think I installed my hard start capacitor on the wrong OEM capacitor. I think I put it on the larger "RUN" capacitor and it looks like it should have gone on the smaller "START" capacitor.

I need to go back up on the roof and check now.
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Old 08-15-2012, 08:53 AM   #10
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Quote:
Originally Posted by herk7769
I learn as well. As I researched this, I think I installed my hard start capacitor on the wrong OEM capacitor. I think I put it on the larger "RUN" capacitor and it looks like it should have gone on the smaller "START" capacitor.

I need to go back up on the roof and check now.
Lol !
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Old 08-15-2012, 08:54 AM   #11
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The same thermostat runs the furnace which is 12 volt.
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Old 08-15-2012, 09:30 AM   #12
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Actually thermostat runs relay or contacts depending on thermostat that runs furnace. If you don't have 12volts to furnance it wont work but ac still will work...
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Old 08-15-2012, 12:03 PM   #13
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Originally Posted by onetonford View Post
Actually thermostat runs relay or contacts depending on thermostat that runs furnace. If you don't have 12volts to furnance it wont work but ac still will work...
Yes; One thermostat but two different sets of control power (one provided by the furnace and one provided by the air conditioner) and contacts.
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Old 08-15-2012, 01:27 PM   #14
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On my Solera the 12volts come from the camper 12 system. not a AC tranformer.
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Old 08-15-2012, 01:47 PM   #15
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The AC control unit is powered from 12V. The thermostat tells it what to do. Check out page 9: http://www.dometic.com/FileOrganizer...llation_EN.pdf
We run 12Vdc and 120Vac through the roof to the AC opening. So if the 12Vdc is dead, the control unit inside the AC would not be functioning. we use the Brisk Air AC's on the class C line.
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Old 08-15-2012, 03:07 PM   #16
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Quote:
Originally Posted by jamiller45 View Post
The AC control unit is powered from 12V. The thermostat tells it what to do. Check out page 9: http://www.dometic.com/FileOrganizer...llation_EN.pdf
We run 12Vdc and 120Vac through the roof to the AC opening. So if the 12Vdc is dead, the control unit inside the AC would not be functioning. we use the Brisk Air AC's on the class C line.
Thank you John.
I had no idea the Class C units had a "Comfort Controller" that has a separate 12VDC run (fused at 3 amps). My Coleman Mach III is not set up that way.

Where is that 3 amp fuse located?

Do all Motor Homes have this type system?

What trailers have this unit?
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Old 08-15-2012, 04:16 PM   #17
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I see the fan motor is twelve volts to circulate air when traveling down the road unlike the trailer unit which have no reason to run the fan when no bodys in the trailer unlike the motorhome which people occupy the whole unit and need to keep cool air in whole unit.
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Old 08-15-2012, 04:36 PM   #18
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So, back to the OP.
There should not be a 12 VDC run to the roof air conditioner, right?
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Old 08-16-2012, 06:17 AM   #19
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Quote:
Originally Posted by herk7769 View Post
Thank you John.
I had no idea the Class C units had a "Comfort Controller" that has a separate 12VDC run (fused at 3 amps). My Coleman Mach III is not set up that way.

Where is that 3 amp fuse located?

Do all Motor Homes have this type system?

What trailers have this unit?
The 3 Amp fuse is built inside the AC module also. We supply that 12Vdc with the same circuit we wire for all of our roof vent/fans. I believe it is more just to power a relay inside than anything...I've never dove too far into it other than knowing what we have to provide the AC module in order for the AC to work correctly.
I am uncertain who all uses the Brisk Air AC's other than us. We don't have set standards even within FR, so each division and product is free to find what works best for them.
Also, I forgot I was in a trailer thread. oops. I didn't mean to muddy up the waters with other product info. Please forgive me.
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Old 08-16-2012, 06:24 AM   #20
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Also, I forgot I was in a trailer thread. oops. I didn't mean to muddy up the waters with other product info. Please forgive me.
No, you are quite correct!

It is not a trailer thread. It is in General Tech.

This happens quite a lot actually and a hazard of putting "generic" tech support by appliance in one place. Sometimes I make assumptions based on my experience (OK, it happens a lot) with trailers and assume it applies to everyone. I am learning.

I had no idea motorhomes could have both AC and DC FEED requirements, since all my trailer air conditioners never did. Lesson learned again.
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