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Old 10-25-2013, 05:04 PM   #1
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Nubie Question. Is it normal for the generator to strain under electrical load ?

I have a year 2000 Hurricane Class A motorhome. The generator has about 250 hours, and the chassis has 23,000 miles. I had the carb cleaned for the generator just a few months ago. I have not used the motorhome yet but I run the generator every 8 weeks to keep the carb in shape.
Question-- I noticed that If i run the A/C using the generator that the generator slows down a bit from the A/C electrical drain. And if I turn on the microwave additionally at the same time, the generator slows down a bit more in its idle speed. When I disconnect or turn off the A/C and microwave the idle on the generator goes back up to a high RPM. IS this normal ?

Does electrical drain actually affect the generator idle speed where it is quite noticeable ? Is that NORMAL ?
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Old 10-25-2013, 05:13 PM   #2
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No. May draw it down slightly with applied load, but should come back to speed (1800 rpm) to maintain. It shouldn't continue pulling the rpms down the more load you add as rpms need to maintain voltage and frequency.
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Old 10-25-2013, 05:28 PM   #3
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No. May draw it down slightly with applied load, but should come back to speed (1800 rpm) to maintain. It shouldn't continue pulling the rpms down the more load you add as rpms need to maintain voltage and frequency.
Would you know what would cause the RPMs to drop under load ?


There is no surging, just a slight drop in RPMs under load .

The drop in RPMs is only slightly (10% or 15% drop) with the A/C on the roof (I have a single A/C unit) but if I run the A/C AND the microwave at the same time, the RPMs on the generator drop off as if the generator is under strain or load. With the A/C AND the microwave on the Generator Slows down about 20 or 25% from the No Load speed.

some additional info....I used to have a surging issue real bad before the carb was cleaned out, but that was resolved after the carb cleaning that was completed a few months back.
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Old 10-25-2013, 05:29 PM   #4
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When you put a genny unload they sound different because the engine is having resistance, kinda like a lawn mower going in thick grass and the engine has to speed up it's a Deeper sound. Check your voltage under load if it's fine so are you.
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Old 10-25-2013, 05:32 PM   #5
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When you put a genny unload they sound different because the engine is having resistance, kinda like a lawn mower going in thick grass and the engine has to speed up it's a Deeper sound. Check your voltage under load if it's fine so are you.

How would I check voltage ?

Would you suggest I connect a voltmeter into an 2 prong house type outlet in the kitchen area ?

ALSO And what is NORMAL voltage range ?
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Old 10-25-2013, 05:43 PM   #6
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When I start my gen it runs at a certain noise level. As I add appliances such as the AC and microwave, it changes pitch and definitely starts to strain. Interesting, my MW works great on shore power. But when I run the gen, the keypad is non responsive until I run the AC, which apparently drops the voltage just a bit. I've not had this looked at as for us it is a non-problem.

You can get a kill-A-Watt to help show the voltage or just a volt meter.
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Old 10-25-2013, 05:51 PM   #7
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When I start my gen it runs at a certain noise level. As I add appliances such as the AC and microwave, it changes pitch and definitely starts to strain. Interesting, my MW works great on shore power. But when I run the gen, the keypad is non responsive until I run the AC, which apparently drops the voltage just a bit. I've not had this looked at as for us it is a non-problem.

You can get a kill-A-Watt to help show the voltage or just a volt meter.
Good to hear from you again Tom !! Thank you for always answering my posts. You are a true friend. Mark
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Old 10-25-2013, 06:11 PM   #8
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When you put a genny unload they sound different because the engine is having resistance, kinda like a lawn mower going in thick grass and the engine has to speed up it's a Deeper sound. Check your voltage under load if it's fine so are you.
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Old 10-25-2013, 08:13 PM   #9
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250 hrs on a 2000 unit, you may want to take it to a generator shop and have them 'load bank' it. May pay to have someone professionally look at it and they can diagnose any issues.
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Old 10-25-2013, 08:15 PM   #10
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Can't tell what the speed is doing by listening to the sound the motor makes as load is applied and you can only tell by using an external RPM meter, or more conveniently, a Hz (cycles/second) meter - which is often included in even fairly cheap digital multimeters.
Yes, check the voltage and the frequency by inserting the test probes into the normal power outlet - but be aware of the hazards involved and know the correct procedure for doing it safely.
BTW don't expect either reading to be rock steady as load is applied and shed - because the control systems generally aren't perfect and don't need to be either in this application,
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Old 10-25-2013, 09:25 PM   #11
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Check voltage - likely normal noise change with load..
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Old 10-26-2013, 06:06 AM   #12
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but I run the generator every 8 weeks to keep the carb in shape.
Small point but running a generator (every month for an Onan) is to remove moisture from the gen. windings. If worried about the fuel/carb. - there are additives for that
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Old 10-26-2013, 11:50 AM   #13
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Can't tell what the speed is doing by listening to the sound the motor makes as load is applied and you can only tell by using an external RPM meter, or more conveniently, a Hz (cycles/second) meter - which is often included in even fairly cheap digital multimeters.
Yes, check the voltage and the frequency by inserting the test probes into the normal power outlet - but be aware of the hazards involved and know the correct procedure for doing it safely.
BTW don't expect either reading to be rock steady as load is applied and shed - because the control systems generally aren't perfect and don't need to be either in this application,
You seem to be knowledgeable in this area. May I ask then....

I seem to be getting some minor surging of the generator with microwave on cooking when a electrical load is applied. I notice that the microwave interior light flickers and coordinates a bit along with the surging/dropping RPM's of the generator when I am cooking with the microwave.

I guess that my main two questions specifically are

1) is it normal for the generator to "fight" or waver in RPMs under microwave load ?

2) If not, then what would cause the wavering/dropping/surging in RPM's and output of the generator ? would dirty carburetor cause it ? Remember, I ONLY get surging/wavering/dropping in generator RPMs with load. Without any load, the generator runs steady strong.

3) I appears form all indications that the voltage or power emitted from my generator is varied ( an assumption from the observation of the microwave interior light flickering coordinating with generator RPM surging or dropping ) . So my question specifically is .....
Is it normal for generators to CONTINUALLY surge in RPMs ( and voltage) UNDER LOAD ?

I do not need a "perfect" operating generator. I bought a used motorhome that is 13 years old and as long as the generator operates the appliances I am fine. I do not want to spend money to replace or repair any electrical components in the generator to improve this condition other than cleaning or replacing the carburetor since I am a only use the RV 2 weeks a year RV operator/user.

But I am wondering If this is normal or if the carburetor needs to be cleaned out or serviced again.

4) PLEASE NOTE THAT ....The generator carburetor was serviced/cleaned out 3 months ago because I was getting MAJOR surging WITHOUT any load BEFORE the carburetor was serviced, and cleaning out/servicing the carb resolved this surging (without load) issue and the generator now runs steady, but I noticed minor surging WITH load, and am wondering if I still have a carburetor issue OR this minor surging WITH load is normal???
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Old 10-26-2013, 01:23 PM   #14
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It shouldn't change RPM except very slightly when the load changes, picking up again within a second or so. I'd suggest getting a "Kill-a-Watt" meter. It includes an electrical frequency selection, so you can tell for sure if the generator frequency drops under load. For systems using ac power, big frequency drops are potentially harmful, particularly to systems with synchronous motors in them.

I would be very suspicious of the generator's governor system. The older models (my rig's an '02, so the generator is probably an '01) have a real Rube Goldberg set-up with springs and piano-wire push-rods. The forces generated in controlling the RPM are relatively light, so a sticky bearing or a slight mis-alignment could be interfering with the governor operation.
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