A reader watched my (really good, if I do say so myself) video about changing out the RV Power Converter and wondered if the power converter could somehow be the culprit behind some VERY strange behavior. Before you read on, you can also check out my page chocked FULL of RV Power Converter how to videos.
Lets read the exchange between the reader and RV52 and see if it can help you out!
Reader question: Why does my RV Air Conditioner quit when I turn on the lights?
Watched your youtube video on converter install, very good i must say . I have a question not sure if my problem is the converter or some other problem and thought you maybe have some insight. First thing I am always plugged in shore power and have turned the battery to the off position(use stationary and as a second home 1/2 a week). , The problem is when I turn on any dome light (which I believe are 12v) or bath vanity the a/c kicks off. I don’t understand, from what I have read a/c runs 120v all outlets. microwave and ceiling fan and 75 watt nook light work fine.
Dazed and confused
John
RV52.com’s answer below has some extra information on RV Air Conditioning Systems and Thermostats!
John,
Thanks for the complement on the video. Its nice to receive and keeps me wanting to make more.
There is the A/C and there are the A/C controls – the thermostat. The thermostat is DC which means that its power comes from the converter. When you turn on any lights running on DC, the voltage level gets dropped low enough for the A/C thermostat to signal “off” to the A/C.
When you turn the lights off, does the A/C cycle back on after a couple of minutes?
I’m assuming you never threw a breaker on any of these scenarios.
When you turn on a light, do the others dim a great deal?
This certainly sounds like your converter. They aren’t expensive (only $100-200 bucks or so) and you can get from Amazon. If you get one, I would love it if you use any of my links to get to Amazon (I’ll get a small commission that does not affect your price at all).
/how-to-video/how-to-all-about-converters/
Your converter should have PLENTY of juice to keep all the lights going and run the thermostat if running well. I’ve also sent to my local RV repair guru’s to get a 2nd opinion.
Thanks!
Marlan
Greg says
Hi Marlan,
I read the above post about one of your readers a/c cycling off when they turn on a dome light in their RV. I’m having the same problem.
When I turn on one of the dome lights (could be any one but not always the same ones), the a/c will cycle off. Although the a/c will cycle fine if the dome light(s) are already on beforehand. Our RV is stationary and permanently connected to shore power. This just happened this season. We’ve had the RV for 6 years now. Up until this season I did not have a battery connected (I was recently told even though we’re permanently connected to shore power, I should still have a battery connected). The converter is a 45 amp Magnetek 6300 series.
Was the issue ever identified with your other reader?
Thanks!
Marlan at Rv52 says
No, the reader never did call or write back. I still think my “theory” could apply – when a new light switches on, there is a brief moment before the converter catches back up to the NEW amount of current needed to maintain the voltage. That brief moment is enough to make the thermostat shut off. I would have thought that the battery would do more to MASK that type of problem rather than make it show up… unless have the battery attached finally aged your converter OR perhaps switched your converter to a different mode of operation. I see that same comment about having a battery attached to shore power too, but I’m pretty sure that the converters supply the current to the DC circuits and then only keep the battery charged when on shore power – which means that the battery doesn’t actually do much. I’d have to question how bad it really is. Lets face it – your converter has lasted 6 years so far. That is pretty good. You would have wore out 2 or 3 batteries. If “right” is determined by the least money, you might have been right. Downside – no battery means than when power goes out – which in rv parks isn’t that uncommon – you are done-for. Some random RV52.com thoughts… repost when you get a definitive. I’d LOVE to know.
Greg says
Hi Marlan,
Thanks for your quick reply and your thoughts. It is a mystery! If I discover what the cause is, I’ll certainly repost and who knows, it may go away as quickly as it appeared!
Thanks again,
Greg
Greg says
Hi Marlan,
I’ve solved the a/c mystery (rv roof a/c cycles off when I turned on a dome light and sometimes even when I opened the fridge…….all those are connected to the 12V power. The a/c would sometimes even cycle ON when I turned ON a dome light!!). I simply put in a new thermostat and that has solved the problem. Evidently there was something defective with the old thermostat that was triggering the a/c to cycle on or off when something powered by the 12V system in the trailer was turned off or on. A small surge must have been being sent to the thermostat to trigger the problem.
Greg.
Marlan at Rv52 says
Very cool that you solved it. A bad thermostat would definitely mess with your AC!
Kirk says
I’ve been having similar problems in my 2000 Fleetwood Pace Arrow Vision. When we turn on the 12 VDC bathroom light, it kills power to other 12 VDC lights in the house, AND to the 120 VAC powering our air conditioners. IN fact, running ANY power causes fluctuations in voltage.
The service manual I read suggested the ECC mod board needed replaced, so I did that, did not change the problems. I used the diagnostic switch on the ECC mod board to run our AC, and removed the T-stat from the wall, still having intermittent power flux without t-stat hooked up.
I used my VOM on the distribution panel and found 6+ volts when the lights are dim, and 12 volts when bright. Since the power is coming directly from the converter, I’m assuming my converter is failing. It’s not a fuse because the power comes back on randomly. I’m going to replace my converter next as it’s 17 years old if it’s the OEM part; not sure as I’m the second owner. Any + comments welcome.
Marlan at Rv52 says
I bought a Progressive Dynamics from Amazon here: http://amzn.to/2aFauln. It wasn’t too bad to install and I made a little video about it.
Anthony says
I believe the answer to a portion of the mystery lies in the connection of what was likely a 6yr old (original) battery, as Greg says, “This just happened this season. We’ve had the RV for 6 years now. Up until this season I did not have a battery connected (I was recently told even though we’re permanently connected to shore power, I should still have a battery connected).”
Remember that virtually everything in a camper is 12V powered. Well, one responsibility on the converter is to charge the battery as you know, however if the battery is “toast” it will gladly drink up more than its fair share of juice. This would not allow for enough power left over for the converter to power things like thermostats, control boards, water heaters, etc… The item affected first would likely just depend on which was lowest on the totem pole.
So while a battery would normally “protect” it can actually cause problems if it is not in proper working order.
Check out thelse two explanation on youtube…
1) https://youtu.be/IGKkHhHlTOM
2)Super, super analogy early on but battery explanation starts at about 03:00
https://youtu.be/JWmalBWVQsQ
Marlan at Rv52 says
Awesome. Thx for the great comment.
Anthony says
By the way, I am learning a ton from your site. Thanks so much!
Marlan at Rv52 says
Thank you for using the site *AND* your kind words. Leave as many comments as you want!
Troy Wilkinson says
I just recently started having this problem. We live in our motor home and have for the past 3 years. I’ve noticed that when I turn on my internal battery charger to high then the problem stops.
I’m going to replace the batteries and the thermostat.
I’ve also been concerned about the converter fan…it’s not been coming on. The last time I heard it come on was in the winter when the heat was on.
I’m wondering if the fan isn’t turning get on, the fan itself spins by hand, but never comes on.
I’ve now had the charger on for 10 minutes and the problem has stopped.
Dave Egy says
when I turn on myAC I lose all my 110 power , I know my batteries are in need of replacement but I”m not sure what the problem is . hooked up my generator and the AC powered up but quickly went down. We are in a bit of a heat wave as well. Thanks for any advice you can give. Dave Egy
Marlan at Rv52 says
What do you mean lose all AC power? Tripped a breaker or fuse? I don’t think your batteries are a factor at all here. Does your generator have an ammeter or do you have any way of seeing if the AC is taking more juice than it should be? I do have online help available via http://rv52.com/rvhelp – you might give them a try – they are 24/7 online RV mechanics.
jmc says
Hello Marlan
I have a 98 gulfstream that recently began the same weird problem and the origin of this thread. My AC works fine until I turn on a dome light, which causes the AC compressor to kick off. (Fan still running) Cycles back on normally. From your advice I assumed it was my converter. I disconnected the converter from the system and put a battery charger on my batteries. My batteries are brand NEW. It still does the same thing. Turn light on and AC turns off. I put a volt meter on the batteries and watched as my son turned the dome light on and the voltage dropped from 12.06 volts to 12.04. Thats it. How could that cause the Thermostat to kick the AC off? I also swapped the rear thermostat with the front one. It still does the same thing? So its not the thermostat. (most likely) What am I missing?
Am I correct in assuming the 12v system does not need the converter as long as your batteries are good and charged?
Also my converter manual says if the output does not read 13.6V the converter is bad. Mine reads 13.4(with output cables disconnected) Once reconnected it drops to 12.3V. What should I gather from that.
Marlan at Rv52 says
Great write-up. If possible, measure the 12V voltage @ the thermostat rather than on the batteries. 12.06 to 12.04 seems ok by me. I’m not 100% sure, but I think the thermostat may come off the converter directly rather than from the battery. I’m not entirely sure if the 12V system connects to the battery directly rather than through the converter. How did you disconnect the converter from the system? BTW – you can get RV mechanics online 24/7 who will know more than me for sure: Find them here: http://rv52.com/rvhelp/
Jeff Cook says
Thanks for the reply Marlan,
Good idea about measuring at the thermostat instead. I disconnected the converter by removing the two main charging leads that come off of the converter itself. The converter manual said they needed to be disconnected to run that test. The AC still works with the converter disconnected. Until I turn on a dome light.
BTW Your link http://rv52.com/rvhelp/ does not take me to where you claim it does. Its a law firm.??????
Marlan at Rv52 says
Aaargh! Keeping up with all the links on a website is like cat-herding. I fixed up the link.
The AC should work as it is 100% connected to AC. So that makes good sense.
My working theory is still that the 12V is drooping at the thermostat. If you measure it at the thermostat and it doesn’t droop, then I completely out of ideas. But I think it will droop! Any betting readers out there?