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Topic: Microwave power light not illuminating when running the generator question (Read 481 times) previous topic - next topic
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Microwave power light not illuminating when running the generator question
In another thread I had commented that when starting the on onboard generator the power light on my microwave does not light till I turn a power source on inside the motor home.  I thought this was normal.  There were a few comments that said this is not normal and should be checked so I’m starting another thread, clarifying what is occurring, and looking for feedback if this is normal or not and comments/suggestions on what to do if this is not normal. 

With the generator off, if I plug the Lazy Daze into a power pedestal the microwave power light illumines, even with no loads are turned on inside the Lazy Daze.  It turns on when the Lazy Daze is plugged in. 

Now if the Lazy Daze is not plugged into anything, all 120volt loads besides the converter are turned off, and I start the generator, wait for it to get up to speed and provide power, then the power light on the microwave will not illumine till I turn on something that is plugged into a 120 outlet.  In another thread a few commented this is not normal and should be checked. 

I do not use the generator often and its generally only run once a month for an hour or two, depending on the outside temperature.  When its run, generally everything is turned off inside the m/h.  The motor home is not plugged into any outside source of electricity besides the on-board roof mounted solar panel.  Fridge is off.  Only things plugged into an outlet is the fridge and microwave.  After starting the generator, I would generally wait about 3 minutes before turning on any loads.  I generally turn on the a/c or heat strip for a load plus maybe a small portable electric heater for a load for the monthly maintenance.  When I turn something on inside the Lazy Daze, like the air conditioning or electric heater, only then does the microwave light illumines. 

Doing some checking I plugged a few outlet/voltage testers into various outlets inside the m/h.  On starting the generator, it takes about 14-15 seconds for the generator to provide power to the outlets.  I hear a click when this happens and the circuit testers show about 118-120 volts but still the light on the microwave does not illuminate.  I’ve plugged a circuit tester into the one of the outlets of the microwave and when the generator switches over the outlet will show as having approx. 120 volts but still the power on light on the microwave does not illuminate.  Only if I turn something on such as the fan for the air conditioning, fridge on electric, or electric heater on heat does the microwave power light illuminate.  With a kill-o-watt meter I checked HZ.  61-63HZ with no load on generator.  Approx. 60.6-61HZ with a heater/air conditioning running. 

I’ve checked the electrical connections in the breaker box (removing the cover) and converter and everything was tight except with the 30amp breaker which was a little loose.  I removed the cover over the transfer switch and there are only wires wire-nuted with electrical tape over them.  The wire nuts seem tight but I did not unscrew them. 

The converted/charger is Model 7345.  The microwave is a Dometic CDMW10MB.  Both original. 

So, is it normal for the microwave display to not illumine when starting the generator and nothing turned on and with no outside source of electricity, besides solar?

JohnF
2003 TK
Re: Microwave power light not illuminating when running the generator question
Reply #1 –
This is not normal, and the microwave has no unusual requirements. If you have a socket tester, the kind with three bulbs that illuminate to tell if the wiring is kosher, I would see if that indicates a discrepancy between generator and shorepower. Will the microwave function even if the lights don't immediately come on?

Steve
2004 FL
2013 Honda Fit
Re: Microwave power light not illuminating when running the generator question
Reply #2 –
I don't have anything to add, John, but I want to say that your description of the symptoms is one of the most complete I've seen in this group, and should help others diagnose the issue. I wish everyone who has a problem would describe it as well as you have.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Microwave power light not illuminating when running the generator question
Reply #3 –
Do you have an inverter in the system, by chance? Some inverters have a stand-by feature that checks for an attached load, and when one is detected, turns on 120 V AC power. Maybe the microwave doesn’t get detected by the stand-by feature, but when something else is plugged in, it does get detected.

How this is relevant to the generator, I don’t have a guess.
2013 27’ Mid-Bath
2005 Honda CR-V
Re: Microwave power light not illuminating when running the generator question
Reply #4 –
As I read your post you are saying you have AC power from the generator.  It looks like you have tested other outlets and the microwave outlet.      The microwave is plugged into a AC outlet.   It looks like your microwave is at fault.  
I have removed the microwave.  It's just a standard microwave without the outside covering. 

glen
personal fine art photo stuff
TF Mack | Flickr
It's all good .......
2014 Twin King
Re: Microwave power light not illuminating when running the generator question
Reply #5 –
"If you have a socket tester, the kind with three bulbs that illuminate to tell if the wiring is kosher, I would see if that indicates a discrepancy between generator and shorepower. Will the microwave function even if the lights don't immediately come on?"

I've tried the socket tester with the three bulbs in different outlets on both generator and shore power and its reads proper wiring.  The microwave will not function unless the power indictor (the steady zero) on it is lit. 

I've also tried plugging the microwave into an extension cord and plugging the extension cord into one of the house outlets, thinking maybe it was related to the microwave outlet or breaker but when starting the generator there no difference. 

JohnF
2003 TK
Re: Microwave power light not illuminating when running the generator question
Reply #6 –
"Do you have an inverter in the system, by chance?" 

No inverter.

JohnF
2003 TK
Re: Microwave power light not illuminating when running the generator question
Reply #7 –
Hi John;  The symptoms of the microwave oven not showing a power light, may just be an inadvertent result of more 'hash' on the powerline. Power pedestals probably have 'cleaner' 110VAC than what the generator can provide.  I wouldn't worry too much about it. It could even be some software feature in the oven. The voltage at the other half of the outlet where the microwave is plugged in shows proper 110VAC, correct?
     You have checked most of the connections that might be problematic. I would make sure that the 'hot' lead (black wire) connected to the bottom of the microwave circuit breaker, in the power distribution panel is tight.
      With a 2003 it is time to check the tightness of all of the screw connections inside the power distribution box. (with No AC power, shore or generator) make sure all of the screws on the neutral buss bar are tight. Check the screw input to the Main circuit breaker that feeds the buss bar, and circuit breaker output screws in the box. These feed outputs to branch circuits. Heating and cooling at these connections with expansion and contraction causes the copper to 'ooze' slowly away from the clamping action of the screws.
     This 'routine' maintenance should be done about every 10-15 years. High power items like the roof air, microwave oven, and the outlet that you usually plug in an electric heater. I would also check the wiring connections at those connections. This is more involved than what I can do at our meetings.
     I have done this distribution box check on a few rig's at the Caravan Club meetings. Usually there are a few 'verging on loose' connections.  One member whose rig I checked at the box, soon after, did have the inlet to the rig burn out at the Marinco socket connection to the rig's romex connection which transfers power to the buss transfer relay at the power distribution box.  It appeared to be a poorly done wire nut connection done at the LD factory.  Between the stranded wire (Marinco socket) and the 10 ga. solid wire of the romex.  The stranded wire had moved inside the wirenut during the assembly process, and was only partially pressed into the large stiff solid wire at the very end inside the wirenut. It is very rare to be able to see the 'autopsy' of a failure like that. Thanks Roger!  Another member did a work around, temporary repair, for the duration of the meeting. (Thanks to John Van!).  That was a 2006 rig. (IIRC).     RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Microwave power light not illuminating when running the generator question
Reply #8 –

Solid-to-stranded connections are a common cause of electrical problems, and that's especially true with wire nuts, because they hide the connection from sight. It helps to use wire nuts that are specially designed for the job, such as those made by 3M, but it's equally important to follow instructions to the letter, including pre-twisting the wires before attaching the wire nut. This video shows how to do it correctly.

I prefer to use Wago connectors when possible, but the ones I've seen are only good for wire up to 10 gauge, so would not be suitable for heavy-duty applications.

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Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
 
Re: Microwave power light not illuminating when running the generator question
Reply #9 –
Tried something different. 

With the generator running and microwave plugged into an extension cord with no loads turned on in any outlet besides a circuit tester with a voltage display.   I plugged this extension cord with the microwave plugged into the other end and plugged into different outlets.  Again, the microwave display light would only lumen if a large load was already running or when I turned the air conditioning fan on high, heater on, or fridge on in electric.  With the air conditioning fan on low or medium the microwave display would not light up.  So there has to be a big load on the generator for the microwave display to illumine.  But once the display lumens I can turn off any of those loads and the microwave will still have power and work.  Now if I again unplug the microwave and plug it back in, the microwave display will not illumine unless there is a large electric load on the generator. 

So I am guessing this has to do with the microwave not liking the power output from the generator.

JohnF
2003 TK
Re: Microwave power light not illuminating when running the generator question
Reply #10 –
Quote from: JohnF  - 
So I am guessing this has to do with the microwave not liking the power output from the generator.

Sure sounds like a poor connection or loose screw in the 120 VAC side of the Power Center or transfer switch, as previously suggested.
That is a very weird problem., obviously a new one to this group.
It is so hard to troubleshoot long distance. Good luck with this.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Microwave power light not illuminating when running the generator question
Reply #11 –
"So I am guessing this has to do with the microwave not liking the power output from the generator."

Trying to think out of the box... would you, by any chance, have access to a 2nd microwave you could sub-in for the OEM? Might offer a clue! ::)
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Microwave power light not illuminating when running the generator question
Reply #12 –
Quote from: JohnF  - 
So I am guessing this has to do with the microwave not liking the power output from the generator.

JohnF
This is what you should see on both shorepower and generator with one of these handy devices...

Steve
2004 FL
2013 Honda Fit
Re: Microwave power light not illuminating when running the generator question
Reply #13 –
I wanted to comment on the above JohnF post regarding the microwave's delayed response when starting the generator.

We have the same model year, a 2003 mid-bath; it has the original Dometic microwave. We have rarely used the generator and most of its hours are from giving it exercise. As far as I can recall, when I start the generator, there is a delay until we hear a "click" as the generator power becomes available. The microwave lights up **after** I turn on a plugged in power load like a ceramic heater or the air-conditioning. I just experienced the exact same chain of events when exercising the generator. The generator started, after a short period I heard the "click" and checked the microwave. No power was showing and the interior light did not turn on when I opened the door. Right after I turned on the air-conditioning, the generator lit up.

To me, this is normal and I am not about to look for a problem where I see none. We see a similar pattern in our home when the electricity is interrupted with different appliances reacting differently to power being restored. As long as it works....works for me.

Steve K
Steve K

2003 Mid-bath
Re: Microwave power light not illuminating when running the generator question
Reply #14 –
I wonder if the microwave light circuitry is expecting a connection to "earth" ground such as would occur when plugged into shore power, but not on generator (where "ground" and neutral are essentially the same thing).  In that case, a heavy load might result in a different sensed voltage level on the ground lug during generator operation.