MEP-804A 24V Alternator no output and RPM Dropouts While Running

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mrosalik

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Hi folks, new here but have been running an 804A on a 20-mile Off-Shore lighthouse restoration job. Our donated 804A alternator has given up the ghost. Been using two 12V chargers to keep batteries up but need alternator. hopefully these photos help identify what brand this is.

Searches for what is printed on a tag on it have come up with nothing so far.20190629_111043.jpg20190629_111054.jpg20190629_111104.jpg

Second issue is random RPM drop-outs or a slowing down. Seems to be when very lightly loaded. Do these have some sort of semi-sophisticated speed control tied to the frequencysetpoint?

Thanks for any help.
 

Guyfang

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Hi folks, new here but have been running an 804A on a 20-mile Off-Shore lighthouse restoration job. Our donated 804A alternator has given up the ghost. Been using two 12V chargers to keep batteries up but need alternator. hopefully these photos help identify what brand this is.

Searches for what is printed on a tag on it have come up with nothing so far.View attachment 770137View attachment 770138View attachment 770139

Second issue is random RPM drop-outs or a slowing down. Seems to be when very lightly loaded. Do these have some sort of semi-sophisticated speed control tied to the frequencysetpoint?

Please define Random RPM dropout. Will the engine just slow down and jump right back up? Or slow down and then pick slowly back up? Or slow down and stay at the lower RPM?

What do you consider "semi-sophisticated speed control tied to the frequency set point?" This is a precise Power gen set. It has a Magnetic Pickup, (Speed sensor) Governor Control Unit, (GCU) and Electric actuator, (EA). They all control speed, (RPM=HERTZ).

Need the answer to the first question, to judge how to help your problem..

Thanks for any help.
.
 

mrosalik

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The engine sounds like it studders and or loses power. The frequency meter will drop way back and or pin to the left under 50 Hz. Sometimes it is a very brief "burble" with quick recovery. Other times several seconds prompting me to want to shut it down.

It sounds like it slows down very briefly and picks back up fast. Other times it seems like it may even stall lasting several seconds.

I found a loose terminal on the 20a alternator Positive terminal. It needed almost one turn to tighten. I'm wondering if that damaged the alternator. The misbehaving is much less since I put two battery chargers on it bringing that voltage back up. When I last went out the batteries were barely 11V each and the starter solenoid only clicked.

The terminals were badly corroded so I fixed that and charged the two batteries with a back up generator. After getting it running I found the alternator was not putting out. It did come back briefly at 28V but only a few minutes. The starting battery meter was in the green then dead.

With the now increased battery voltage and less "events" is why I'm assuming that the Frequency/RPM control may be electronic versus purely mechanical like the 6-71N in the boat.
 

mcii

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Suggestion, just take it [alternator] to a alternator shop get it checked out and or fixed as required, easy to put back on and you know it is good to go either way, it pass's check and or it gets repaired .. mac/mc
 

Guyfang

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All of the TQG family gen sets do not work well without proper DC voltage. Fix your battery charging problem first. Then let's see if it runs better. How many hours on the set? Is your fuel source clean there? Have you downloaded the TM's?
 

mrosalik

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Thanks but not quite that easy. It's a 4-hour drive for me to northern Michigan. Then load and prep the boat. One to two hour boat ride to the 641.jpg lighthouse where the generator is.
 

mrosalik

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Yes thanks I have downloaded TMs. Lots to read. But I'm so thankful that information is available. Lots of old stuff to keep running out there.

Thank You!
 

155mm

Chief and Indian
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For the pure'ist out there, stop reading now.....

if you cannot get your alternator repaired or replaced, order this noco battery charger.

https://smile.amazon.com/gp/product/B004LWTHP2/


hook it up to both batteries, or hardwire to back of slave receptacle, plug in to convience plug on front, there now its fixed.

the noco is NOT a 20-30 or 100 amp alternator, it is only 7 amps, BUT, it will recharge the batteries in an hour or 2. If you have gel batteries(optima), it also has a safe charge option for those as well.
 
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mrosalik

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Thanks. The Convenience Plug in front needs to be made to work again too. Maybe the fuse. And the fuel gage.

With the TMs and you guys helping we can fix her up.

Thanks
 

155mm

Chief and Indian
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On the back of the gfci, there is a reset button, I trip that one more times than the push button on the front. It says 10amps, so thats normally the problem

IMG_3399[1].jpg
 
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