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Daneast1

Furnaces cause lights to flicker

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I’m using my class A 40 ft diesel to live in this winter in Colorado. What I just started experiencing after 6 mo. of living in coach is when both furnaces kick on the lights start flickering and furnace fan slows down considerable usually causing the O2 sensor to alarm. This is happens when plugged into 50 amp or 120 volt. Help!

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Hey Bill, 

Have 4 that were all replaced last August before trip from TN to CO. But, no I haven’t actually checked them other than when starting the 8 kw generator and running engine occasionally. Guess that might be a good place to start, uh?  

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Tighten and check all connections as you have a bad one or more 

Check power relay from battery's

Test with shore power off so it is all house battery s  

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If they are acid batteries, look at water level.  When was the last time you took the coach out for a drive?  Also, ran the generator for a couple hours on 50% to full load?  6 months is a long time for a DP to just sit, they don't like that.

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20 hours ago, Daneast1 said:

Hey Bill, 

Have 4 that were all replaced last August before trip from TN to CO. But, no I haven’t actually checked them other than when starting the 8 kw generator and running engine occasionally. Guess that might be a good place to start, uh?  

 

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Thanks guys for the input! I did check batteries today. They are good. Ran engine and started generator for 30-40 mins. Last driven 2 weeks ago but for only a short distance, (20 miles). Still same problem. I’ll have to check power relay from battery. Problem is when I run both furnaces and 2-3 lights is when lights flicker.

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You inverter/charger should be maintaining your batteries at around 13.3-13.6 volts. Have you checked what you voltage is?

 

Jim                          

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4 hours ago, Daneast1 said:

Thanks guys for the input! I did check batteries today. They are good. Ran engine and started generator for 30-40 mins. Last driven 2 weeks ago but for only a short distance, (20 miles). Still same problem. I’ll have to check power relay from battery. Problem is when I run both furnaces and 2-3 lights is when lights flicker.

As the battery's checked good and you are having this problem when on shore power. Do you have a surge Guard on the power pedestal? What is the incoming voltage when the lights flicker? Possible problem that your voltage is low and the inverter is not able to produce enough 12V power. Low voltage is a big problem in some parks.

Bill

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You said the  batteries were good. I just can’t imagine the water level has not dropped after 6 months of steady use. The water was up to the split rings on each cell ? And as mentioned , you still might have a bad battery.  Remove and clean all the battery connections.

running the MH engine for a few minutes is not good. Either let it sit or drive the MH for at least 30 minutes or more. The genset as mentioned should be run once a month for about 1 hour or more on at least half load, this is to keep the generator wiring etc dry.

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Hey, thanks again for input. I did verify water/acid level to be good. Voltage is 13.3 - 13.6 on each battery. I am currently only plugged into 120 at cabin. I have run generator under load and still experience problem with lights and noticed if both furnaces try to start fan speed goes to almost zero and lights turn off completely. Problem seemed to have started right before I left the campground plugged into 50 amp, but has continued after move. 

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2 hours ago, Daneast1 said:

Although one house battery showed good, it wasn’t. Y’all tried to tell me (point me in that direction) Thanks for the help!

Glad you found the problem.

Bill

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Well, I thought for sure I found my problem. I’ve checked all connections, all 4 batteries, each fully charged and almost 14 volts out to coach. Guess I’ll check the battery relay as suggested above. I would think it was the furnace fan/fans since that is the only time I notice a problem, but either one running separately causes the problem and either one start and run fine. Both will not run together. Any other thoughts/suggestions. I’m stationary and 100 miles from nearest dealer. 

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I just re-read the original post, and the OP mentioned that this happens on 50-amp or 120v service. That would seem to indicate to me that the problem may not lie in the 12v battery bank at all.

Do the furnace units work on 12v? If so, have you tried to unplug from the shore power to see what happens? One thought that I have is that if the furnace operates on both 120v and 12v, then somewhere inside the unit there is a power transformer. My Suburban is actually a 12v furnace, and when it's being operated on 120v the internal converter simply makes 12v from the 120v. If this transformer is shorting or starting to burn out, then every time it kicks in it's going to cause problems.

Have you checked the wiring all the way from the 120v breaker panel to the furnaces? Look for a loose connection, any signs of heat or damage, or anything else that would indicate a problem or arcing.

Have you opened the covers on the furnaces to see if there are any signs of over heating? Any areas on the wiring that look discolored? Have an acrid odor (from plastic melting internally)?

What seems strange is that both units seem to do the same thing. Odd that both would go on the fritz at the same time. Unless, of course, if there was some type of external problem which affected them both, like having the 12v connected with reverse polarity or a short or loose connection in the 120v circuit which feeds them.

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Do you have access to an amp clamp device? If so, check the amperage draw of the furnace motors. Short of a loose wire or too small gauge wire between 12 volt source and the motors is only cause that would commonly cause the lights to flicker. 12 volts connected with reverse polarity will only cause the motor to run backward on dc current. Also what type lights is your coach using, florescent, led, halogen, or incandescent/resistive wire. If florescent, there may be an arching effect in the motors that may cause them to flicker, in that case, the brushes may be worn and not seating well on the commentator within the motors, or simply showing a need for the bearings on the fan to be oiled, or replaced. Just a few more things to check.

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Dan.

Like Richard, I went and re read all that the information that you supplied.  Have a couple of questions.  Do you have the same issue when your on Generator?  Have you looked at your Transfer Switch?

If you don't have the problem on Generator, I would suspect a bad plug on your shore power cord, or a bad connection. 

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It would really help if you could tell us what make/model of coach this furnace is in, as well as what make/model of furnace you have. Right now we're all trying to troubleshoot with you but it's tough when we don't have enough informaiton.

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Well, I thought for sure I found my problem. I’ve checked all connections, all 4 batteries, each fully charged and almost 14 volts out to coach. Guess I’ll check the battery relay as suggested above. I would think it was the furnace fan/fans since that is the only time I notice a problem, but either one running separately causes the problem and either one start and run fine. Both will not run together. Any other thoughts/suggestions. I’m stationary and 100 miles from nearest dealer. 

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Thanks again for each of your inputs/comments! Furnaces are Atwood model 8525-IV DCLP. Either will run on 12v without shore power. Running generator makes no difference. Have not looked at the transfer switch. Amp draw is 1-2 with either furnace running. All lights are led. I would think the fan brushes could be worn, but would be surprised since problem occurs with either furnace running. No smell of wires or plastic burning. Power transformer could be a problem if I can locate. It’s like the power converter, looked everywhere and unable to locate. Thinking it could be a combined inverter/converter. It’s a Magnum Energy. Coach is a 2009 Coachmen CrossCountry 383fws, 330 diesel.

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I just looked at the manual for this furnace and it appears to run on 12v. Is this correct for your furnace or do you have both 12v and 120v feeds to the furnace? Do you have a 120v breaker for the furnace?

Are your LED lights running from your 12v system or your 120v system?

If your LED lights are running from your 12v system & your furnace is running from your 12v system, then I'm starting to wonder if you've got both of these running somehow on the same circuit, possibly in a way that doesn't provide enough current flow when you run everything at once. What I'm talking about here is either a too-small wire gauge or a connected which is poorly crimped or in some way compromised as to restrict current flow. Since the problem seems to have started suddenly after having worked properly for a while, I wonder if a wire or connector somewhere got knocked partially loose or was damaged in some other way. I've seen something as simple as a staple used to mount something cause a problem when it pierced the insulation in a wire and caused an intermittent short.

At this point if this were mine I would be looking for a way to run the furnaces from a totally separate power source (like a spare battery) and start doing some binary testing to isolate the problem area.

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The lights flickering could be cause by a poor ground at or near he furnace.  Yearly, I go through both 120 vac and 12 vdc panels and check for tight connections.  Shaking the trailers down the road will shake wiring and plumbing loose.

Ken

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Just wondering, is it possible you have the coach battery disconect switch off? (Sometimes referred to as the salesman switch)  

If so you could be running the furnace, lights, everything 12 volt off your charger/ converter. Without the added resource of the storage batteries this could cause your lights to dim and furnace blowers to slow..

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Yes, furnace is running on 12v. No 120v breaker for furnace. LED,s are running from 12v. Yes, since it started suddenly after a 6 mo extended stationary stay, I too think it may be wire not making or loose. I’ll start checking all connections. Battery disconnect is in the “I” position. 

 

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