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Generac Generator Shuts down


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  Yeah I know, many are NOT fans of Generac RV Generators, but that's what was in the RV I bought and works good EXCEPT for one problem which I want to ask about. Its a Generac 4 KW Model 4700.

 It starts fine, runs smooth and powers the AC or Microwave or coffer maker or hair dryer all fine, no black or blue smoke, no sputtering, no coughing, nice clean warm gray NON fouled spark plug BUT after maybe 30 minutes if running the rooftop AC IT SHUTS DOWN........No its NOT out of fuel, NO the ignition system is otherwise fine, ITS LIKE A SUDDEN SAFETY SHUT DOWN such as low oil pressure or low oil (full of fresh  oil) and I suspect it may be a safety thermal shut down due to overheating ??????????? It ONLY shuts down after 30 mins of AC use, when its real hot outside, NEVER any other time and AC works fine plugged to shore power.......I have all other 120 VAC loads like fridge and charger etc OFF when I run the AC in extreme hot weather. If I wait maybe 15 to 20 mins it starts right up and repeats the cycle and eventually shuts down again.

Anyone ever run across a faulty safety thermal limit switch that's opening although it shouldn't at wrong temperature ??? Think of reasons for overheating ?? Its clean and free underneath where the screen is where the fan circulates engine cooling air??

What you think is wrong or what should I try ???? When it happens its just like you hit the kill switch IT SHUTS DOWN  grrrrrrrrrrr

 Guess I need to have my meter handy and locate any thermal or other safety limit switch (oil or overheating etc)  and right when it shuts down see if its open !!!!!!!!!!!!!! 

 Sure I like Onans but this is what I'm stuck with lol. If I cant fix it I will deal with that when the time comes. 

John T

Edited by oldjohnt
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Make sure you have good air flow around the generator. Have you tried running it with the compartment open? There is no bottom to the compartment is there? The Oman is open on the bottom for cooling.

Ron C.

2013 Dynamax Trilogy 3850 D3

2000 Kenworth T2000 Optimus Prime

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Put a box fan in there with it so when genny runs so does the fan, See what that does / Check for loose wires that could build up heat / Feel those wires after it shuts down see if you get a hot one / Maybe just maybe the AC is overloading and getting too hot and drawing lots more amps then its supposed to ? Might take a few cold ones to think this over :)

 

Jim Spence

2000 Dodge 3500 1 ton QC 4x4 dually 5.9 diesel LB

BD exhaust brake, 6 spd manual trans

34CKTS Cedar Creek 5er, Trail-Air hitch

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Sounds exactly like an over temp shut off. You "should" have an over temp light on your genset(?)

Could be a few things going on there that could lead to an over temp.

1. How long has it been since the oil filter was changed/checked and are you using a viscosity appropriate for the ambient temps (SAE30)? A synthetic, like Royal Purple, might do better dissipating heat.

2. How long since the carb has been cleaned? Even slight varnishing in the ventura or on the needle valve can cause your genset to run a skosh lean and run hotter than normal. Remove the air filter and blow a "good" amount of carb cleaner into the intake. Don't worry if it stalls your gen. Let it sit for a few and restart it. You can repeat that a couple 2 or three times. A few ounces of sea foam every once in a while can help prevent future buildups.

3. The oil temp sensor (mounted on top of the oil filter housing) may need to be replaced. They "do" go bad occassionally, but it's a real simple replacement. IIRC... your's is likely to have a 270 temp sensor. You might consider going to a 284. 

4. And of course... air flow. Those suck a lot of air so it's always important that there is adequate ventilation. If your compartment is somewhat enclosed the addition of a small fan might help improve circulation.

That being said... Generac's "do" have a bit of a reputation for over heating issues, but nothing that can't be cured. 

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1 hour ago, oldjohnt said:

what should I try ?

I would try running it with an electric heater of similar wattage to the a/c load just to confirm that the problem is the load and is not related to something happening in the a/c unit. I doubt that it is an a/c problem but eliminating that as a cause is so easy, why not be sure?

 

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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J0hn T h0w many amps can that geraccku put out 4K watts ? I know I have 2 - 2k in parrallal Hondas which put out 13.2 Amps each and they really bark starting an AC. and continious running I think they are rated at 3200 watts

Jim Spence

2000 Dodge 3500 1 ton QC 4x4 dually 5.9 diesel LB

BD exhaust brake, 6 spd manual trans

34CKTS Cedar Creek 5er, Trail-Air hitch

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9 hours ago, Yarome said:

Sounds exactly like an over temp shut off. You "should" have an over temp light on your genset(?)

Could be a few things going on there that could lead to an over temp.

1. How long has it been since the oil filter was changed/checked and are you using a viscosity appropriate for the ambient temps (SAE30)? A synthetic, like Royal Purple, might do better dissipating heat.

2. How long since the carb has been cleaned? Even slight varnishing in the ventura or on the needle valve can cause your genset to run a skosh lean and run hotter than normal. Remove the air filter and blow a "good" amount of carb cleaner into the intake. Don't worry if it stalls your gen. Let it sit for a few and restart it. You can repeat that a couple 2 or three times. A few ounces of sea foam every once in a while can help prevent future buildups.

3. The oil temp sensor (mounted on top of the oil filter housing) may need to be replaced. They "do" go bad occassionally, but it's a real simple replacement. IIRC... your's is likely to have a 270 temp sensor. You might consider going to a 284. 

4. And of course... air flow. Those suck a lot of air so it's always important that there is adequate ventilation. If your compartment is somewhat enclosed the addition of a small fan might help improve circulation.

That being said... Generac's "do" have a bit of a reputation for over heating issues, but nothing that can't be cured. 

 THANKS EVERYONE, I just heard from a retired small Generator repair friend and much of what he said mirrors all of you gents great advice and my own suspicions.......He said he had seen thermal switches cause shut down even though actual conditions didn't warrant it. One switch he found was Part number G075281,             Temp 284 F        LIKE YAROME MENTIONED

Oil was recently changed to Castrol Magnatec Full Synthetic of the viscosity labeled on Genset.

Has a new (about 1 year ago) carb and air filter.

I tried it with the side compartment door open and it made NO difference.

I haven't yet experimented or looked at any fuel mixture adjustment on the recently installed carb. I DO KNOW it could possibly be a tad lean ??? its certainly NOT over rich, she NEVER black smokes nor exhibits any over rich gas odor and plug is a nice warm gray color PLUS she never stalls or coughs when the AC compressor kicks in. I might see if I can richen it 1/4 turn if it has such an adjustment that is ???

 

MY PLAN after all you guys and the retired gents advice is :    I am going to order that new 284 Degree switch,,,,,,,,Change oil with Synthetic again maybe a different brand this time,,,,,,,,,clean air filter,,,,,,,,,,,,,look into a slight fuel richening,,,,,,,,,,,,,,If all that fails do the extra fan thing which sounds like a good idea to me

 

THANKS EVERYONE

John T 

 

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1 hour ago, Kirk Wood said:

4000 watts  ÷  120V = 33.3A  

Supposedly Kirk but my 2000 Hondas each are only rated at 13.2 amps. I did plug my 14A skilsaw in and it promptly dumped the breaker  so my 2000s paralled are only good for 26.4

Jim Spence

2000 Dodge 3500 1 ton QC 4x4 dually 5.9 diesel LB

BD exhaust brake, 6 spd manual trans

34CKTS Cedar Creek 5er, Trail-Air hitch

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10 minutes ago, Devilishjim said:

Supposedly Kirk but .............................

That is rated amps and you have to know how the manufacturer derived the information. Typically they use peak ratings, not real world or continuous load ratings. The math is valid but is only as accurate as the data supplied. Also, the ratings are based on new equipment and most actual outputs will slowly decrease with age. The other factor to consider is the starting current of your saw and that is probably more than the rated 14a. The builder of the generator wants you to see the largest number that he can support, while the saw manufacturer is going to show the lowest for it. 

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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53 minutes ago, oldjohnt said:

 MY PLAN after all you guys and the retired gents advice is :  

Sounds like a solid plan. Couldn't hurt to shoot a little carb cleaner to ensure it's not a sticky needle valve. I doubt it's the AC. Your Generac has over voltage protection so in the event of excessive current demand the genset will keep running... it just stops juice output.

21 minutes ago, Devilishjim said:

Supposedly Kirk but my 2000 Hondas each are only rated at 13.2 amps. I did plug my 14A skilsaw in and it promptly dumped the breaker  so my 2000s paralled are only good for 26.4

That's because running 2-2000watt gensets in parallel limits the output to the continuous output rating (vs. max rating) in order to sync the current between the two sets.

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4 hours ago, Yarome said:

Sounds like a solid plan. Couldn't hurt to shoot a little carb cleaner to ensure it's not a sticky needle valve. I doubt it's the AC. Your Generac has over voltage protection so in the event of excessive current demand the genset will keep running... it just stops juice output

UPDATE: I just found a 293 Degree Generac Thermal Switch for my Make Model and Serial Number Genset which I'm ordering Monday from whichever supplier has one in stock. I'm going to go ahead and buy a new Oil Pressure Switch (its in series with thermal right by the oil filter) and replace both and change the oil soon as the parts arrive. I will let yall know if that fixes the premature shut down...Perhaps as suggested an "Oil Cooler"  ????

THANKS AGAIN TO YALL

John T

Edited by oldjohnt
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8 hours ago, Devilishjim said:

J0hn T h0w many amps can that geraccku put out 4K watts ? I know I have 2 - 2k in parrallal Hondas which put out 13.2 Amps each and they really bark starting an AC. and continious running I think they are rated at 3200 watts

Jim, good question, here is some info FYI.

1) If  you're talking straight Watts and as Power = V x I, 4000 watts at 120 volts = 33.33 Amps. 3600 Watts = 30 Amps 3600/120.

HOWEVER that's nowhere near the "rest of the story" You may see KW and you may see KVA ratings on some equipment

2) As you well know the labeled ratings may or may not be hyped up a bit (surely not lol) plus there's the "Continuous" and "Surge" ratings

3) A motor might temporarily draw 5 to 6 times its normal running current at startup which is why an x rated genset might not start an AC  even if it could supply the normal running current. IE they can RUN an AC but they just cant START IT LOL. That's where an AC Soft Start Unit like discussed on here recently might allow a certain sized genset to start and run an AC which it couldn't otherwise.   

4) KW is NOT the same as KVA. KVA is "Apparent Power" while KW is Actual or Real Power available to do work.

5) KW = KVA x Power Factor.  In a pure Resistive circuit the PF is Unity one so KW and KVA are the same there.

6) In a high inductive load such as a motor (like the AC unit) current lags the voltage and you get a lousy less then one Power Factor which is why power factor correction capacitors (current leads the voltage) are added to counteract the inductance and improve the power factor. 

ANHYWHO my Genset starts n runs my AC (like fine for 30 minutes) if I can stop it from overheating or repair any inaccurate thermal or pressure switches causing it to shut down ????????????? Maybe a 293 degree (versus 277 or 284) thermal will allow it to keep running??? As noted an "Oil Cooler" perhaps????

Best wishes

John T

PF_Power_Triangle.jpg

Edited by oldjohnt
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  • 2 weeks later...

SUCCESS UPDATE

So, I installed a new 293 Degree Thermal (old was 274 or 284 best I could tell),,,,,,,,,,,,,,,,,,Changed oil from Castrol Synthetic to Royal Purple Synthetic (but don't think that mattered),,,,,,,,,,,,,,Got the fuel mixture just a tad richer (Yaromes input), although, she started n ran n powered AC just fine before.....................

Other day it was hot n humid and it ran the AC fine like 90 minutes trial NO SHUT DOWNS              Yayyyyyyyyyyyyyy

But only time will tell

 

Thanks to all who responded

 

John T

  

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  • 11 months later...

I am not sure if i am too late to this conversation. The QP 40 generator muffler should have it's own compartment just like all enclosed rv generators. The muffler compartment needs to be the very last compartment before the air blows out the bottom. I believe the muffler need to be taking out, and a exhaust pipe made that bolts to the engine, and goes out the bottom of the housing. The part of the exhaust pipe that is inside of the housing  i would wrap it good with exhaust insulation wrap. The exhaust pipe i make come out the bottom of the housing i would run it away from the generator as far as i can and mount the muffler that i took out of the generator or better yet mount a automotive muffler. That should stop the overheating problem, or at least help. 

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Edited by Steve Wiggam
Trying to post what i already wrote
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Generac QP 40 rv generator that overheats at about 90F or hotter outside is just one thing of many things i have searched on the internet and wasted many hours of time to not find the answer sometimes all night long and not find the answer. The internet has let me down many times. So i had to figure out the stuff by myself. I figure that i should make posts, and videos for my YOUTUBE channel of stuff that i can't find on the internet. Thanks Steve W.

Edited by Steve Wiggam
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On 6/16/2018 at 1:37 PM, oldjohnt said:

UPDATE: I just found a 293 Degree Generac Thermal Switch for my Make Model and Serial Number Genset which I'm ordering Monday from whichever supplier has one in stock. I'm going to go ahead and buy a new Oil Pressure Switch (its in series with thermal right by the oil filter) and replace both and change the oil soon as the parts arrive. I will let yall know if that fixes the premature shut down...Perhaps as suggested an "Oil Cooler"  ????

THANKS AGAIN TO YALL

John T

Generac added a oil cooler to the QP 40 rv generator ,it's the newer one's that are painted black. I don't know if that fixed the overheating problem. I really believe taking the muffler out of the housing would make it run cooler.

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THANKS STEVE, I just noticed your responses, all make sense, here are my thoughts.

YESSSSSSSSSSS that darn muffler located INSIDE the housing isn't a great thermal design I agree as it releases sooooooooo much heat alllllllllll inside the enclosed housing. If a person reconnected the exhaust with the muffler OUTSIDE the box I'm sure that will help immensely, it about HAS TO....

 UPDATE since a year ago...……... I installed the new 293 Degree oil temperature thermal switch,,,,,,,,,,,,While I doubt it made any difference whatsoever, I changed to Royal Purple Full Synthetic Oil,,,,,,,,,,,,WHAT I THINK MADE THE MOST DIFFERENCE  is I added a squirell cage blower and ducted it so it forces/stuffs more air into about 1/2 of the housings fresh cooling air inlet side,,,,,,,,,,,,,WHAT ALSO MADE I THINK A HUGE DIFFERENCE is I adjusted the governor so it now runs no load at 62 HZ and 120 volts and under full load its running at 60 HZ and 115 + volts, it was dragging down (voltage and frequency) quite a bit before under full load, but NOT now. I think the fuel mixture is fine for now, not lean but not too rich

 So far (but hasn't been exposed to running the AC over maybe 90 minutes when its over 90 outside, only time will tell) its ran a long time and NEVER shut down due to overheated oil. Operating at the proper voltage and frequency and stuffing more air into the boxes inlet just had to help in my opinion  

 HOWEVER if it ever does I think the first thing would be to re route the exhaust so its NOT direct under the housing,,,,,,,,,,,,,if not too difficult try one of the oil coolers you mentioned,,,,,,,,,,,,maybe try what you spoke of regarding heat shielding the interior muffler if that doesn't cause other bad outcomes????

BOTTOM LINE its actually very very infrequent when dry camping I run the AC. I would typically move or go up in elevation where its cooler but if its just too hot to get to sleep  I might run it a while before bed to cool down then go back to all my vent fans and rooftop vents and and fans etc....Also if the genny ever gets too troublesome I would replace it with a new Cummins Onan, but for now its working great and if it ain't broke I'm NOT gonna fix it lol

QUESTION FOR YOU STEVE  For another issue to quiet it down a bit more I've considered running a larger auto style muffler OUTSIDE THE BOX in series with and attached to the exhaust pipe it has now...……..HOWEVER I fear that might restrict the exhaust air flow too much (can cause more heat problem) and/or might burn up the exhaust valve...……...WHAT DO YOU THINK ??????????????? Its NOT anything that needs done actually, just a method under consideration to quiet it down a bit more 

 John T  (barely got through Thermodynamics when in electrical engineering school, its NOT my cup o tea)

 

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  • 1 year later...

My generac quietpact 75D  Diesel does the same thing or sometimes it will run for a minute and quit or 30 minutes or 3 days.  So mine doesn't seem to be an overheating problem.   Then wait 20 minutes may start and stop in one minute or run for 10 minutes.  Has a mind of it own.   Have replaced exhaust tube and oil pressure sensor.   Now put voltage meter on it and when its running its at 14 and as soon as voltage drops to 12 it shuts down.   Any ideas anyone

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Dwight 

Sounds to me that possibly your disconnect silinoid my possibly be releasing when down to 12volts. But next question I'm having is if at 14 volts why does it drain down to 12 volts is your convertor charging correctly or inverter secondly if they are then you must have a dead cell in one of batteries draining voltage 

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2002 Generac Primpact 66G. Runs perfect, makes power for about 15 minutes and then.appliances, AC etc shut down due.to no power, generatorstill running fine, just not making power.  Shut it down for 20-30 minutes, starts back up fine and makes power for 15 minutes, repeat cycle.  Area is all clean, oil is good, ran with door open or closed.  Any thoughts?

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18 minutes ago, Scott Bradley said:

Any thoughts?

Welcome to the Escapee forums. It sounds to me like the circuit breaker on the generator is opening. What actions do you take to get it to take a load again and start all over? 

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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I had same problem. 
 

 Mine has an integrated inverter with 2 grills on the ends and a fan on one side, it’s part of the generator, it’s not 3rd party. mine is mounted in the storage box next to it. I had folding chairs packed too close to it and it was over heating and shutting the generator down.  I tried EVERYTHING you tried until I discovered this. I cleared the area out and it runs all day in 95 degree temps. So simple, but I just didn’t see it. 

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