Microwave Problem

[jluchuk]

I am looking for some ideas on a microwave problem I have on my 2000 Larson Cabrio 290. When hooked to shore power the microwave works fine. However when the generator is suppling power the microwave looks like it is working but it does not heat anything up. The turntable rotates, the light is on, and the fans are running but nothing heats up. I don't know why it will work on shore power but not the generator. Any idea anyone has would be appreciated.
Jerry

 

[jan verbanck]

Re: Microwave Problem

Have you measured the output voltage of your generator yet? Some microwave have a kind of protection against low voltage. This means that maybe the auxiliaries will work such as light but the coils won't activate.
It's just one possibility, but check it out ! (anything in the manual on this ??)

 

[hard-3]

Re: Microwave Problem

have your generator frequency checked make sure it is 60 cycles. if rpm is not correct, frequency will be off. microwave may not work with wrong cycles.

 

[jluchuk]

Re: Microwave Problem

I will be going up to the boat this weekend and will check out some of these things. Will provide feedback next week. Thanks.
Jerry

 

[jluchuk]

Re: Microwave Problem

I found the problem. When hooked up to shore power the microwave works fine, however when trying to use it with the generator it does not heat. One of the Larson techs told me that it was possible that other AC accessories were drawing power at the same time as the microwave and would result in no heat on the microwave. He suggested shutting off everything else and use just the microwave from the generator. I tried this and it worked fine. There is nothing wrong with the generator. The microwave was the only thing affected and only the heating part. It is no big deal. If I need the microwave on the water I can shut off other AC items and use it. Thanks for everyone's advice. Jerry

 

[waterone1@aol.com]

Re: Microwave Problem

Jerry,
That sounds all fine on the surface. However, I would want some real answers. If the voltage is sagging so bad from the genset, that it will not operate the microwave when other items are drawing power, is there a problem with the genset, the breakers or the wiring ?
Since most boats use the same wiring and branch breakers for both shore power and generator power, that would leave only two items. Either the main breaker on the genset is not working properly and thus not tripping when the total power used is exceeding the generator's capacity ( dangerous) or the genset is not performing properly.
My guess is that the genset is not running on both cylinders properly or there is some other problem with the genset. As the load is increased, the genset should open it's throttle to maintain the voltage. In other words, as you turn on loads ( water heater, lights, microwave, etc.) you should NOT hear the genset's rpm's decrease.
I advise having this checked out further.

 

[jluchuk]

Re: Microwave Problem

I will look into it further but I had the genset checked out when I bought it and the surveyor said it was fine. The Larson tech said this is normal for a microwave. Everything else on the boat can be on including hot water heater, air conditioner, etc. and works fine. Everything on the microwave works except the heating part. The genset RPM stays constant so I am not sure what may be wrong. Most marina service technicians are not qualified to find a problem like this. Thanks for the input.

 

[waterinthefuel]

Re: Microwave Problem

If the rpm doesn't change it IS the generator. We have an onan 4000 genset and it can run the mach 1 ac and microwave no problem. It kicks it in the tail but it works. How many watts is your microwave?

 

[waterone1@aol.com]

Re: Microwave Problem

Not to beat a dead horse too badly....but... A marine surveyor will give you a good overall opinion on a boats condition. In most cases, if the oil is clean, the genset starts and is not making weird noises and is able to power an appliance or two, the surveyor will give it a clean bill of health. Unless someone has load tested the genset and monitored the output with an osciliscope, for frequency, voltage and waveform, you really don't know if it is performing properly. In this case I doubt it is.
I noticed the above post and have to respond : When piling on large loads, you should hear the rpms change MOMENTARILY, however within a second or so, the rpm's should stabilize. They should not decrease as the load increases.
What brand of genset is this ? In most cases there is a dealer/service center in the area that can send a tech to look at the unit. In other words, someone that knows generators inside and out instead of a boat dealer or marina. The microwave may only be an inconvenience, however as more of us are bringing laptops, computers, video games for the kids on-board, etc, clean power is a must.

 

[jluchuk]

Re: Microwave Problem

You are not beating a dead horse and I do appreciate you help and information because I know what you are saying about surveyors etc. The generator is a Kohler 5E serial # 0658296, It has 88 hours on it and at the start of the season I replaced the impeller and plugs. I ran it this past weekend and it does just as you say when I turn on another load. The rpms drop for a second and then come back. I had the air on and the microwave worked. I can't test it with the hot water heater on because it has been winterized. I will check around to see if there is a service tech in the area. If I had an oscilloscope I could check it myself but I gave mine up a long time ago because I never used it. I will follow up and post what I find. Thanks for the help.
Jerry

 

[littlebookworm]

Re: Microwave Problem

This is one other aspect to take into account: the microwave itself. Being on a boat can damage anything electronic, including a microwave. They are usually not marine specific, but rather just a small household unit, not really made to take much abuse. See if you can borrow another microwave to plug into the boat's electrical receptacle to see if it works properly. If it does, a visit to your local appliance dealer for a new microwave is in order. Good luck, and let us know the outcome. Hy

 

[jluchuk]

Re: Microwave Problem

I wanted to let you know that I won't have an update for this problem this season because i had to winterize the generator because the boat is being pulled for the winter and I have no way to run it in storage. However I did speak with a Kohler technician who told me that the max output for this generator is 41 amps and it is possible to push it to its limits. He said a microwave heating element takes approx 12 amps. However he believes I may have a problem with the engine not quite running at the correct RPMs affecting the correct outputs. He suggested I measure at the generator, the voltage which should be 125 VAC and the Hertz which should be 62 cycles with no load. This should be done with a meter and the rpm adjusted to meet these specs. He believes this is the problem and will fix it. I will do this but it will now have to wait for the spring. Thanks for all the advice and have a great winter. Jerry

 

[waterone1@aol.com]

Re: Microwave Problem

Jerry,
In a round about way, he is thinking the same thing I am.....the genset is not meeting specs. However, I am thinking the problem is not related to "open" no - load, but more related to "under load". In my opinion, the problem is not in the generator section, but in the motor section. I have a hunch that the motor is not performing when the generator is seriously loaded, in other words, the engine has a problem maintaining the proper rpm's when the generator is " pushed to it's limits. The no-load spec he gave you is useful, but I would be more concerned with the spec for 100% load. This could be as easy as setting the no-load rpms, or as difficult as finding out what is wrong with the carb, or spark plugs or something else when it is fully loaded. Let us know what you find in the spring.