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Topic: Fridge runs on shorepower or propane, but not on generator while driving... (Read 972 times) previous topic - next topic
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Fridge runs on shorepower or propane, but not on generator while driving...
Ok, we have an unusual situation that stumped the folks at Morro Bay at the tech talk.

I am just checking if anyone else ran into this situation.

We have a 28K Onan generator (likely the one that came with our '89TK).  We have the electrical wire from that joined with the electrical wire for shore power going in a separate Progressive ATS.  Then a wire from there going into our Progressive power center.

During our longer drive to Morro Bay, we tried out the trick of running the generator to keep the fridge cool.  However, even though the fridge showed the AC light on, the fridge acted as if it had no electricity at all  and lost temperature steadily over the hours of driving, way more than accountable by any sun on the rig or the temperature inside or outside of the rig.

The fridge is a Dometic 2008 model - it is on a 15 amp breaker.
The fridge works fine on propane (before, during, and after our trip).
The fridge works fine on shore power (before and after our trip).  I thought maybe something got knocked loose or we had a fridge failure and the timing was coincidence, but the fridge worked fine on shore power on a test tonight.
The generator charges batteries just fine when we are boondocking (on trip and previous trips).
We have run our previous Air Conditioner while exercising our generator - so it can handle running higher amps (note, the battery was at 100% during those times).
But the fridge didn't work at all when on the generator while driving. 

We have not :
1) Tested the fridge running on the generator when we are not moving - the next test to do. 
2) Tested the voltage coming from the generator but I know I have seen 12-13 amps on our battery charger regularly and I think I remember seeing the amps higher (15 or higher).  We don't let the batteries (two 6V 210 batteries) run down much, maybe 85% or 75% before we charge them, but we do see it a little higher when charging on shorepower vs generator (makes sense, more juice coming in).  I am wondering if the generator might not give enough amps and the refrigerator won't run. 

Here is some thoughts, someone who knows more about the refrigerator and generators might be able to answer this. 
We have a 28K generator so it should be able to provide 23.3 amps (2800W / 120V) - maybe less because it is 30 years old though seems to work fine.
I am wondering if the fridge will show the AC light but not actually work if it doesn't get a certain level of wattage/amps (we have a 15 amp breaker for it, maybe it won't work if it doesn't get the full 15 amps or something close to that amount).
We didn't have full batteries when we were running the generator while driving.  So likely our charger was using some wattage/amps, but the first time we ran the generator while driving the battery started at 95% charged and we ran it for several hours - our smart charger should not have pulled a lot of amps to finish off that charge, especially after the first hour or so.  I think at that level of charge, our battery monitor only shows a plus 2-3 amps charge.  The second time we tried it the battery like started at 85% charged and I think we ran the generator only for a few hours, so I could understand if for that period the battery charger was taking a chunk of the current.
Note, we did not have anything else running except the fridge and maybe a tiny vampire amount (we don't have an LP detector added yet - an upgrade for this LD, which is the only big vampire I have read about in the forums).  We can simulate this doing more testing:

3) Running the battery down and test running the generator  without the battery charger on and with the battery charger off to see what the fridge does.

Anyone else have this experience?  Or other guesses of what is going on?  Or can confirm my possibility of the fridge not running if it doesn't get a certain level of amps?
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #1 –
Jane and Scott,
I think you are running into the typical absorption refrigerator problem.

It looks like you have  tested the 120 VAC adequately, the A/C runs on either the AC or Generator.  The ATS appears to work and because you charge batteries on shore or generator power.  You have 120 to  the charger to charge the batteries at 12 to 14.4 depending on the battery type.

 My 1988 MB came with a "Super-Smart" 3 way refrigerator with propane on it has trouble holding  temperature while moving. I can hold a freezer temp of -5 F frequently.  I assume you have a model year 2008 Dometic 2 way refrigerator.  I recall you said yours was replaced.  Two issues are likely here.
1. The refrigerator has been changed and the gap to the outside wall is too big.  My 1991 Coachman Econline van conversion has this problem with the original refrigerator.
2. There is too much air flow around the back side coils while moving.  The Dodge/ Chevy Roadtrek owners figured this one out I believe.   These units pulled engine heated cooling air in through the floor board.  They blocked 50 to 75% of the floor board openings and performance improved while traveling. 

Before you worry tooo much, remember, " My 1988 MB came with a "Super-Smart" 3 way refrigerator with propane on it has trouble holding temperature while moving."  Other LDO's  stock their refrigerators with cool packs to deal with this problem.  The alternate is to travel with it off, if the trip is only a few hours. 
Rodney
1988 Mid Bath
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #2 –
While running the fridge on generator, check the AC voltage at the fridge connection, and if that looks fine, check the wiring at the fridge outlet with a tester, e.g.:

https://www.homedepot.com/p/Dawson-3-Wire-Socket-Tester-DET301/300101768?keyword=socket+tester&semanticToken=212t000000+%3E++st%3A%7Bsocket+tester%7D%3Ast+cnn%3A%7B0%3A0%7D+cnr%3A%7B8%3A0%7D+cnb%3A%7B9%3A0%7D+oos%3A%7B0%3A1%7D+pt%3A%7Bsocket%7D%3Apt+rt%3A%7Btester%7D%3Art+dln%3A%7B562768%7D+tgr%3A%7BExact+match%7D+qu%3A%7Bsocket+tester%7D%3Aqu

Hopefully this will give you a clue. If nothing results from this, then if you normally start on propane, try starting the fridge from warm on shorepower, and see how it does.

Steve
2004 FL
2013 Honda Fit
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #3 –
"I am wondering if the fridge will show the AC light but not actually work if it doesn't get a certain level of wattage/amps (we have a 15 amp breaker for it, maybe it won't work if it doesn't get the full 15 amps or something close to that amount)."

For what it's worth, those fridges typically draw about 350 watts or 3 amps at 120 VAC. So it seems unlikely that it's not getting enough juice.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #4 –
Andy, thanks for fridge amp usage - that blew my theory.  We do have a kw measuring device we could double check this with,

Rodney, our clearance between walls to fridge are small (nice after reading about problems others had with this). Having hot air not pulled out (or pulled in) to the fridge cavity was my original thought until Morro Bay attendees were mystified. Previously we did shorter trips so didn't worry - just kept the fridge door shut and there was no noticeable change in temperatures. The longer for us Morro Bay trip (10 hr drive) was the first time we tried running the generator while moving.
Our engine and generator exhaust is on the non fridge side of the rig - the generator itself is under the TK lounge area. I don't remember anything unusual in the fridge area under the rig. We could put one of our temperature sensors in the fridge wall cavity to test temps on our next trip.

Jane

Sent from Yahoo Mail for iPad
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #5 –
When you notice the problem again I would start with checking for power at the outlet that the fridge is plugged into.  The outlet is accessible from outside the motor home behind the fridge cover.  Use a voltmeter, circuit tester, or voltage tester and check for power.  The light on the front and inside the fridge runs off of 12V(battery power) not 120v(generator or shore power).  Although if there is no 120v power you should get a trouble light on the fridge(depending on the fridge) unless there is something wrong with the bulb/circuitry.  On my 2003 T/K when the generator starts I do not always get power to the microwave(the display does not light up).  But as soon as I plug sometime into the outlet by the sink or turn on the overhead air conditioner the microwave display will light up. 

JohnF
2003 T/K and 1987 MP w/Roof Sleeper (for sale this spring)     
2003 TK
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #6 –
John - I am not athletic enough to be testing the fridge outlet while DH is driving :) but yes testing the refrigerator outlet with our voltmeter is on our testing plans, though that does not look like the problem based on Andy's response that it only used 3 amps.

Jane

Sent from Yahoo Mail for iPad
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #7 –
Jane, I think you are misunderstanding what I was trying to say.  I was wondering if for some reason your generator did not switch power over.  Assuming the engine was running before you started the generator.  With the vehicle engine running the house batteries will charge off of the alternator and maybe the converter did not since any demand.  The fridge outlet in my 1987 MP is on the same breaker as my converter.  Maybe the generator needs some type of demand to start applying electricity.  When the outlet my microwave is plugged into has power the display will light up.  When I run the generator in my 2003 T/K for its monthly exercise the microwave display does not always light up.  But when I plug something into an outlet or turn on the air conditioning it causes something to happen and suddenly the microwave has power to it.  I keep a circuit tester in the motor home just for that purpose, to switch the power.  Once plugging that circuit tester into different outlets I could not get power to any of the outlets till I turned on the fan in the air condition then all of a sudden the outlets had power.  Maybe something like that occurred.

Granted that does not explain why you didn't get some type of trouble light on your fridge. 

JohnF
2003 T/K and 1987 MP w/Roof Sleeper
2003 TK
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #8 –
John, thanks for the clarification.

Our chassis alternator does not charge our coach batteries   We are not set up for that - no wires from cab connected to power center or direct to the battery. 

Our refrigerator is on a different breaker than the converter.

With the generator on and not on shorel power we get 120V - run microwave, etc.
We do get the startup screen on our microwave when the generator is running (that was our confirmation the ats 30 second delay was past and we did have electricity into the coach).  Also the cpap will run when nothing else is running (a small draw, much less than the refrigerator):   Our converter is likely also charging the battery when we are seeing these other things running.

At this point I am laying odds that something is trapping hot air in the fridge vent area when we are driving.  But I want to do my test of using the generator while parked to see how the fridge works.

Ok what you described sounds strange to me.  Electricity should be there / not there irregardless if there is a small draw vs a large one.  My understanding from an electrical engineer is that  the electricity doesn’t actually flow down the line unless something is demanding electricity.  I have seen led lights on a dimmer switch not work correctly (didn’t dim smoothly / turn off all the way but’s that was because the dimmer switch didn’t handle low watts/Amps well.

Since most power centers have that built in 30 second delay and if you have a separate ats box like we do another 30 second delay and I think a separate ems also has a other 30 second delay.  So it could be anywhere from 30-90 seconds after the generator turns on before the electricity comes into the coach.  Do you think you might be running into that delay and it was a coincidence that when you turned on the air conditioning that the delay was up by then?
I know we tripped over that delay(s)  a couple of times until we learned to listen for a click from the power center which told us electricity was now coming to the coach.
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #9 –
Quote from: Jane and Scott  - 
John, thanks for the clarification.

Our chassis alternator does not charge our coach batteries  We are not set up for that - no wires from cab connected to power center or direct to the battery. 

Our refrigerator is on a different breaker than the converter.

At this point I am laying odds that something is trapping hot air in the fridge vent area when we are driving.  But I want to do my test of using the generator while parked to see how the fridge works.


Since most power centers have that built in 30 second delay and if you have a separate ats box like we do another 30 second delay and I think a separate ems also has a other 30 second delay.  So it could be anywhere from 30-90 seconds after the generator turns on before the electricity comes into the coach. 

Jane

You LD was Factory equipped with a diode battery isolator, it was mounted under the hood, on the drivers side fender.
The previous owners of your LD did a lot of strange stuff to its electrical system and this may be causing issues that we have not seen before.
Recent LDs used a heavy-duty solenoid to connect the starting and coach batteries together, when the engine is running and its alternator is producing power. You might want to recreate the battery connection.

Unless the refrigerator's is incorrectly installed or the vent has been modified, it should operate fine while traveling, running on either propane or the generator. This is not a common problem except with older refrigerators that have age-related reduced cooling capacity.
When driving in hot weather, I have noticed our LD's refrigerator runs a little warmer and requires lowering the thermostat to compensate .

The 30 second delay is performed by the ATS (automatic transfer switch) and not by the Power Center.
The Power Center is just a box where the fuses and circuit breakers are located .
If the EMS has a built-in delay, this time will be added to the ATS's delay.

I'm confused why the refrigerator would 'see' a difference between generator and shore power and wish I could see it myself and have an hour to go through the electrical, tracing the circuits with a voltmeter.
Remote electrical troubleshooting can be nearly impossible, a reason why I'm hesitant to respond, especially when I do not know the electrical competency of the owner.
I don't want anyone to get hurt or killed, high voltage is not the place to learn about electricity.

Have you tried running the refrigerator on generator power while sitting in the your driveway and if so, have you checked the voltage at the receptacle? 
Measuring the amperage used by the refrigerator, while on generator power will tell you if the heating element is working properly, you can also check the chimney to see if it is hot. You should not be able to hold your hand on it.

A cheap device for measuring 120-VAC power usage is a Kill-a-Watt meter, a useful device for around the home .
P3 P4400 Kill A Watt Electricity Usage Monitor - Low Temperature Alarms -...

Larry
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
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: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #10 –
Larry, yes the first owners redid tons of things and the second owners let things be disconnected when something was worked on and not reconnected.  So we are learning tons replacing old stuff and getting things back up and working.  Adding in charging from an alternator is on the rv fix up list but way down on our list since we are not missing that ability right now.

The refrigerator will run well on propane while driving, but we choose not to do that as our first choice (we did do it for a few hours coming back from Morro Bay while driving thru the desert - not while in LA traffic).  2-3 hour drives we didn't notice any significant rise in the fridge temperature, but the longer driving to Morro Bay showed a significant rise over 4-5 hours (like 5+ degrees at night on a cold rainy day)

When we installed our new power center (what Progressive called the ac/dc distribution center, charger, converter - all in one box), I swear there was a 30 second delay it did.  It might have been a choice we could set.  I am 95% sure (not 100% only because that was over a year ago).  I remember thinking did we want a 60 second delay or not (we figured it really didn't matter and the delays has a purpose we liked).

We did check voltage at the refrigerator while on shorepower a while ago and it was fine (did this while checking something else).  But not while on a generator (no shore).
We typically don't sit and run the refrigerator on AC for extended periods of time as we have it on propane regularly, so I need to do that test.  But fixing this issue is not top of our list because we do not have a longer trip planned again where we are driving more than a couple hours to get somewhere (morro bay next year is the only planned one) - so I am just giving it a little time every week or two.

Yup, we have the kilowatt measuring device and a voltmeter.

Rodney talked about flow issues causing some problems, again something to test out.

I am strong with electricity (I have done entire houses, redesigned from street to throughout the house, including dealing with unusual issues like relay systems for lights). 

This issue stumps me also but it happened consistently each of several longer driving days going to and from Morro Bay.
Andy confirmed the amps drawn is small (3 amps), the generator charges other items at a higher amperage (e.g. recharges batteries), and the fridge runs fine on shore power while parked.

I plan to:
Test with the generator while not driving.  Probably do that with the battery charger on and with it off, checking fridge outlet voltage.
It could be the fridge is getting older, we do notice a slight but noticeable difference that it seems to work better on propane than shore power, it is getting older (2008).

If the fridge doesn't work on the generator sitting still, that will be a big clue and I will do some further voltage testing of the generator and the outlets.  At that point Larry, I will take any electrical debugging trips - PMs is fine or I do skype (and similar programs).   I respect electricity and stay on the safe side.

If the fridge works fine on the generator while not moving, we will test while driving with temperature sensors in the area behind the fridge, just to confirm the temperature raises more than it does sitting - but that will wait until our next trip.  Too bad there is not a voltmeter with bluetooth (yeah Larry I know you don't like bluetooth but it would be handy to get voltage readings while driving).  Ooooh, I could set up an extension cord to the plug next to the entry way door and just test that extension cord now and then while driving.  A different outlet but should be similar output from the generator - Just to double check.
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #11 –
"Ooooh, I could set up an extension cord to the plug next to the entry way door and just test that extension cord now and then while driving."

Brilliant idea! I was thinking you could run the voltmeter leads outside to accomplish the same thing but I like your idea better.

But, isn't the AC outlet next to the fridge in the outside compartment common to all AC outlets?  ::)
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #12 –
Steve yes, but it would be difficult to get an extension cord from the outside frige outlet to the cab though something coupe likely be jury rigged up, If there is something off with the generator voltage it should show in all the outlets so using the closer outlet above the countertop next to the entry door should work,

Jane

Sent from Yahoo Mail for iPad
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #13 –
I wanted to update this.

We took another long trip at the end of the summer this year. 
I wanted to test the theory (reported by other RVers on other forums) that a refrigerator that works when parked but not when driving can be because air is coming over the top of the RV and down the fridge vent - trapping the hot air inside the vent so the fridge can't cool off as well.

We put a piece of reflectix up on the forward side of the cap for the refrigerator, temporarily duct taped in place.
It worked like a charm.  115 during the day (much warmer than our last long trip), a long 8 hour driving day (with stops) and the refrigerator stayed cool.
Jane

Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #14 –
Quote from: Jane and Scott  - 
I wanted to update this.

We took another long trip at the end of the summer this year. 
I wanted to test the theory (reported by other RVers on other forums) that a refrigerator that works when parked but not when driving can be because air is coming over the top of the RV and down the fridge vent - trapping the hot air inside the vent so the fridge can't cool off as well.

We put a piece of reflectix up on the forward side of the cap for the refrigerator, temporarily duct taped in place.
It worked like a charm.  115 during the day (much warmer than our last long trip), a long 8 hour driving day (with stops) and the refrigerator stayed cool.


Our refrigerator has stayed operational for dozens of long, hot, highway drives, and held the set temperature.

Dometic has used several styles of vent covers, most are directional, with a slant downward on the front and open at the back.
If the cap is working properly, it should have a slight venturi effect and draw air up through the chimney.
You may have the cap on backward, producing downward pressure when moving.

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: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #15 –
Quote from: Jane and Scott  - 
I wanted to test the theory (reported by other RVers on other forums) that a refrigerator that works when parked but not when driving can be because air is coming over the top of the RV and down the fridge vent - trapping the hot air inside the vent so the fridge can't cool off as well.

Alex Rutchka wrote about this problem as he tracked down the issue on a 2005 MB.  He concluded with a similar theory (air flow over the vent interrupted the chimney effect).  His solution, which I copied, was to add a 12v muffin fan near the top of the vent to keep air flowing.

'Frig warming up on the road

I've found that this solution does make a difference on long driving days.  I also suspect that it help my aging (2003) fridge to cool a little better than it would without the help. 

Your solution (the piece of reflectix, no electricity or moving parts) is more elegant. 

Rich
2003 MB
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #16 –
When I first bought my LD,  the refrigerator was barely cooling.   While investigating what could be done to improve this situation,  I came across a company that manufacturers products to improve air flow. However, due to leakage of the unit I bought a new dometic refrigerator.  But, I also bought products to improve airflow for both inside the refrigerator box and outside.   The company is RV Cooling Warehouse,  rvcoolingunit.com 
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #17 –
Quote from: parussky  - 
When I first bought my LD,  the refrigerator was barely cooling.   While investigating what could be done to improve this situation,  I came across a company that manufacturers products to improve air flow. However, due to leakage of the unit I bought a new dometic refrigerator.  But, I also bought products to improve airflow for both inside the refrigerator box and outside.   The company is RV Cooling Warehouse,  rvcoolingunit.com 

That's the easy way. I did it my way.
KoKo: Cooling the Refrigerator With Muffins Fans

Fans inside the refer and two fans in the vent stack. Someone improved on powering the stack fans with a small solar panel.
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy
Re: Fridge runs on shorepower or propane, but not on generator while driving...
Reply #18 –
I am not surprised that many RVs (LDs included) don't have the issue of this topic.
We have removed old items that were not longer working off our roof, so we have much less stuff up there than most owners which means different air flow.

Yes, we have a standard shaped cover for the fridge vent, it doesn't go down all the way to the RV roof leaving a significant gap. We even checked quite some while ago if it was a standard cover and if the current ones were lower to the roof (yup, standard model, the front structure was the same as the one we had).  If someone had solar that was a few inches above the roof and reasonably close to the refrigerator vent, it would direct air up and over the vent.  We have nothing on that side of the roof, so the air likely goes just above the roof and right into that gap.

I think I mentioned, but  maybe didn't, that at one point early on we found what looked like de-laminated 1/4" plywood - very old - just loose inside the fridge vent area.  We of course took it out (I could imaginable what might happen if it fell down onto the coils).  But nobody could say what that had been for (originally provided more windbreak?) or if it was just a scrap piece of wood that had gotten under the vent cover and fell in.

We read about fans pushing the air out, but the reports of if it improved refrigerator cooling for people were mixed, so we have not done that (yet).

Bottom line, we proved what caused the problem and are glad we can do a permanent fix that is easy.
Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.