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Old 08-13-2018, 03:14 PM   #1
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Generator Run Hours: Precision Plex Hours do NOT Match Meter on Generator, Isata 5

Okay, so I am a total nerd and I just happen to know the number of hours that were on our generator the last time I looked at it (42.1). This past weekend, I decided to do the initial oil change on the generator and when I checked the touch screen (Precision Plex) in the coach, it said a “staggering” 52.1 hours. No big deal, I just assume that my wife was out in the coach getting it ready for our next trip, it was hot outside and she fired the generator to run the AC during the week.

So, I start the generator to warm it up and get ready for the oil change. I let it run for all of 10-15 minutes-ish while I have the AC running to put a load on it. After the aforementioned 10-15minutes, I shut the generator down and to do that, I use the touch screen, which displays the hours (on the manual mode screen). Now, the generator hours are being displayed at 54.3 hours. Wait a minute! I just ran the generator for 10-15 minutes and it accumulated 2.2 _HOURS_! Walk outside and as to be expected, the hour meter on the generator itself has only accumulated a few 1/10ths of an hour!

Huff and puff and go inside….”hey honey, did you run the generator in the RV this week?”

……”yes, it was hot outside”

……”did you run it for more than _10 hours_?”

…….”No, I ran it for less than an hour”

That means that between my wife's "less than an hour" and my 10-15 minutes, the Precision Plex thinks that the generator has accumulated more than 12 hours.


In the pictures below, you can see the current difference. Those pictures were taken within seconds of one another.

Why would the Precision Plex be showing one hour reading and the mechanical meter on the generator itself be showing a different number?

I believe the meter on the generator. I do not believe the meter on the Precision Plex, so how do I make the Precision Plex match the meter on the generator?

How do I prevent this in the future and keep them synced up?
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Old 08-14-2018, 06:48 AM   #2
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Gen 135.2
PP 134.7
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Old 08-14-2018, 10:44 AM   #3
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Gen 135.2
PP 134.7
That actually makes more sense that what I've got going on. It seems entirely plausible that Onan/Cummins does a "run test" (or whatever) at the factory before shipping the generator. Then, when the generator is installed in the coach, the Precision Plex is set to 0 hours.

So, seeing 0.5 hours more on the generator than you do on the PP kind of "adds up" for lack of a better term.
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Old 08-15-2018, 01:08 PM   #4
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Brian (or anybody that knows),

How did the Precision Plex hour meter and the hour meter on the genset end up with a major discrepancy?

How do I reprogram the Precision Plex to match the genset?
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Old 08-15-2018, 01:37 PM   #5
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This is the first time I have ever seen this. Have you reached out directly to Precision? I will discuss this with engineering during our product meeting tomorrow, but I have them on several projects already.
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Old 08-15-2018, 02:04 PM   #6
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my Freightliner dash output reads 521, yet the manual 'odometer' on the generator reads over 560.... oh well, I guess Onan ran the generator to make sure everything was 'A o.K.' before sending it out!
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Old 08-16-2018, 08:06 AM   #7
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We replaced the tank level monitor/generator unit in the wet bay. When we did this the generator hours went to zero. Has started counting from zero again. But does not match actual hours. Appears that the sending unit has a timer that measures how long you run the generator but does not store the number anywhere else so that the computer does not keep a running total. The sending unit does store it locally so if you unplug it and plug it back in it does remember that number. Since it doesn't read the timer on the generator it may not be accurate.
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Old 08-16-2018, 03:17 PM   #8
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We replaced the tank level monitor/generator unit in the wet bay. When we did this the generator hours went to zero. Has started counting from zero again. But does not match actual hours. Appears that the sending unit has a timer that measures how long you run the generator but does not store the number anywhere else so that the computer does not keep a running total. The sending unit does store it locally so if you unplug it and plug it back in it does remember that number. Since it doesn't read the timer on the generator it may not be accurate.
I called Precision Circuits yesterday and can confirm what you are reporting here. The Tank Monitor in the wet bay is taking a +12v signal from the hour meter on the generator and starting a clock. When the generator is stopped, the +12v signal goes away and the clock stops. This is all done from that monitor and displayed on the touch screen in the coach.

I asked if there was any way for me to re-set the hour meter to match the hour meter on the genset. Answer was ‘No’.

I asked if there was any way to order a new one and have that new one programmed with the correct hours on it before it ships. The answer was ‘No’.

The guy I talked to on the phone said he had never heard of this issue before. I know it’s hard to diagnose this kind of stuff over the phone and I am not sure where to go with it. I suppose the simplest thing would be to just shrug my shoulders and say “oh well”, but I just hate it when stuff that is supposed to work, doesn’t. If there were a mismatch like others were reporting and that mismatch stayed consistent, I would understand, but that’s just not the case.


*sigh*…….oh well.
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Old 08-21-2018, 05:29 PM   #9
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Mine has a difference of about 5 hours. Its a diesel gen that will outlast me so I a good with it
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Old 08-22-2018, 02:06 AM   #10
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Can you not just disconnect the tank monitor in the wet bay (at least from where it’s getting +12V from the hour meter) for the next 12 hours of generator use?
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Old 08-22-2018, 02:12 AM   #11
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oooh...good suggestion. It seems like it would work....I vaguely recall that he thought it was mis-tracking hours, not just delayed/gapped, but greater than 1 to 1. I have seen those panels get wet and act goofy....mainly sending bad tank readings. I have not heard of an accelerated gen meter, but I have learned long ago that anything is possible.
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Old 08-22-2018, 03:22 PM   #12
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Mine has a difference of about 5 hours. Its a diesel gen that will outlast me so I a good with it
Yeah, I think I am going to land squarely in this camp and just shrug my shoulders. It’s really not a big deal and I know the hour meter on the genset itself is working just fine, so I do have a known good number to reference.

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Originally Posted by mookieblaylock View Post
Can you not just disconnect the tank monitor in the wet bay (at least from where it’s getting +12V from the hour meter) for the next 12 hours of generator use?
That is a good thought! I suppose the only downside would come from the fact that the monitor in the wet bay is sort of the “brains” of the operation in terms of _all_ the monitor(s). The touch screen in the coach is just displaying the info that is being stored in that monitor box/brain thingy. So, unplug that and the black, grey and propane level monitors go away too.

Quote:
Originally Posted by bclemens View Post
oooh...good suggestion. It seems like it would work....I vaguely recall that he thought it was mis-tracking hours, not just delayed/gapped, but greater than 1 to 1. I have seen those panels get wet and act goofy....mainly sending bad tank readings. I have not heard of an accelerated gen meter, but I have learned long ago that anything is possible.
It is mis-tracking hours as well…..and it did get wet as well (that whole black tank issue thing). I’ll keep an eye on it, but I’m not going to fret it too much at this point.
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Old 08-22-2018, 08:09 PM   #13
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Another wild card may be an auto gen start.
It starts the gen, without the plex knowing.

My plex board has been changed, so it's out to lunch on hours.
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