Fischer Panda Question...

[HMBJack]

I have the standard Fischer Panda 4200 in my 2006 330 Express. It currently has about 450 hours on it.


I am experiencing a mysterious condition that even the FP Technicians are stumped about. Thought I'd share my story with you and see if you have any suggestions.

After running my generator for about 3 hours, the RPM's (and voltage) suddenly begin to fluctuate up and down.
The generator doesn't stall but I can see on my panel the voltage going from 120V down to about 33V then rising back up to 120V then dropping again. It will do this repeatedly but never stalls.

I have found that when this happens, if I turn off the generator and let it rest for 5 or 10 minutes, it will start up and run smoothly again. It therefore seems like something in there gets HOT and needs to cool a bit - not sure...


In my search for the root cause, have done the following to no avail:
- checked electrical connections to all thermo sensors (3),
- replaced the fuel pump and fuel filter
- replaced the relays to the starter and fuel pump
- replaced the water pump impeller,
- changed and checked the oil level,
- checked the coolant level
- checked the tension on the water pump belt

Any suggestions?

 

[ElyseM]

have you plugged in a separate voltage meter to an outlet? does that fluctuate at the same time? if not... good luck, ron

 

[HMBJack]

Thanks Ron but no, I have not tested voltage elsewhere in the boat. Not sure what that could conclude or prove.
To your point, I know the A/C shuts down when the voltage drops down to like 33 volts momentarily before it rises back up to 120V momentarily before again dropping down again.

The voltage fluctuates because the generator itself fluctuates (RPM's going up and down like a yo yo). And yes, I need luck on this one as I'm baffled... Might it be a bad fuel solenoid? Could that get hot after 3 hours of use? The FP Technician says the solenoid either works or doesn't so it's probably not that.

 

[ElyseM]

"I know the A/C shuts down when the voltage drops"

not in the original post. so you know the meter is reading somewhat accurately. i'm not even close to a tech, so no real insight other than troubleshooting like you.

maybe the fuel lines themselves are being affected with the heat? you may want to find a diesel site or lawnmower site and post some questions. from the manual, looks like a simple engine, so maybe you could get a simple answer. like will exhaust back pressure have an effect (how long are the mufflers good for?).

also, are the stator coolant pump and lines ok? any corrosion in the interchange block? my exhaust manifold corroded thru at like about 60 hours and almost blew up my boat, so not sure the quality of some parts.

hope all ends well, ron

 

[ElyseM]

one other thing. i breezed the manual and couldn't find a "thermostat" ?? does it not have one? full water flow without "on-off" switch? like i said, not a tech. ron

 

[HMBJack]

Thank you Ron for your thoughts and brain storming. Something in there is getting hot and causing the generator to want to shut down or fuel (or air?) starve. It never actually shuts down though. I'll keep at it and check and test everything.

 

[wspitler]

My 2007 acted similarly. The solid state relays in the voltage control box get hot. Mine actually partially melted. They provide boost capacitors when a load is added. The replacement relays are higher capacity than original. One of mine was bad, but I replaced both since they (FP) upgraded the capacity. My unit has four capacitors that are activated by two solid state relays. The new upgraded relays are 42-660V AC 50AACeff (boost) relays. I'm betting either those relays or the capacitors are your problem You can test the capacitors, mine were fine, but make sure to ground them out or they could bite you. The voltage control box on my 2007 300 is behind the panel in the aft cabin, port side and has enough cord left to take it out into the galley for troubleshooting. There are also two varistors across the relays and their part number is SIOV Type s20K510. I think they are there to minimize EMI issues. The relays are about $50 a piece from FP. The relays boost the generator when a load is applied and mine were obviously overheating. You'll be able to see if they have gotten hot when you open the voltage control box. Good Luck!

 

[wspitler]

Items #13 page 25 of the 4200 parts list. I tried to attach it, but it would not accept a pdf file.

 

[HMBJack]

Thank you Bill for taking the time to supply such detailed information! Excellent info here!

I spoke with another Technician today at FP (named Bob). He was very helpful and was describing things noted in your response above - most of which I do not understand BTW.

Anyway, Bob said for me to disconnect wires 5 and 6 from the thick gray cable that comes from the generator and leads into the AC Control box. These wires are for the Boost Capacitor (per my notes in talking to him). Bob said to be sure to tape off these two wires as they deliver high voltage. He said disconnecting the boost capacitor (wires 5 and 6) will not harm the generator in any way.

So today, I did exactly as he said and my generator ran under a load flawlessly today for 4 hours! Previously it would start to act up in 3 hours or less.

So, I frankly don't understand why the disconnect of the boost capacitors works but it did. So far, this seems to have fixed my ocillating RPM issue.

Does this make sense to you?

 

[wspitler]

I don't have a circuit diagram handy, but maybe if one or both of the relays were failing intermittently it could cause what you describe. The problem with simply disconnecting the boost capacitors is that they are a designed element of the asynchronous generator circuit and are designed to help the generator accommodate load surges, like when the AC compressor, hot water heater, or stove comes on line. The relays are easy to test for a qualified tech, as are the capacitors themselves. I think that FP engineers upped the amp capacity of the relays for a reason. If you can find a tech that understands generator circuits, I'd replace the relays with the heavier ones. My guess is that with the boost gone, you may have a generator sag and drop the voltage under high load. You can test that easy enough and maybe the boost capacitors are redundant, but I doubt it.

 

[HMBJack]

Just got off the phone with Bob in the Technical Support Dept. of FP.

Bob said the boost capacitors in my AC Box is a second set and by disconnecting them, he said I should not observe any performance issues. If there are issues, a new AC Box runs about $1,400. He said he would not upgrade the relays because it will not necessarily improve anything (I'm not sure why but that is what he said).

He advised to: 1. Use the generator regularly, and 2. to apply a nice medium load of 15-20 amps by using one major appliance at a time. I have been doing this and he said this is perfect. For example, in most cases, I would only operate ONE of the following: Water Heater, A/C, Microwave, or stove top. This is easy to do while in the cabin at the AC Panel.

So, if I do observe performance issues, I guess I will do the $1,400 solution or send my AC box to FP for evaluation. It is comforting for me to at least know that if I see performance issues, I can zero in on the relays and or a new AC control box. Thanks for all of your help Bill. I appreciate it greatly and feel you got me on the right track here.

 

[wspitler]

I was also told that earlier models only have two boost capacitors. Ours has four, two sets of two operated in pairs by the two relays I mentioned previously. The engineers from FP didn't put two more capacitors and a relay in the box just to make it more complex I'll bet. You will probably be fine until the two that are still connected or the relay that activates them starts failing. I wouldn't buy a $1400 box for what is most likely $150 in parts and an hours labor if you can find a good tech. Good Luck and you'll probably be fine!

 

[HMBJack]

Yes agreed on all counts. Thanks and I'll just have to see how it goes running on 2 of 4 capacitors.