Vibrating Load Meter..after installing new battery

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Murph

Pre-takeoff checklist
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Murph
Switched out my 5 year old Gill 7035-28 with a new one today...did a voltage test before the install, its was 13.1V Using a Fluke meter. The old battery below about 1600 RPMs the meter would viberate...by that I mean just sit there and the needle shake, but once it got out of that range it would settle down and become steady. Rarely would it hit 20 amps. This new battery its swinging about the full width of the gauge ,and is never steady, how ever it will come off the very high reading. The voltage is a steady 14.1 with no fluctuations. Alternator is about 2 years old..

Its a Piper PA28-140....fluctuating load meters arent unheard of but as I said, this was fine untill I installed a new battery ..Thoughts and test recommendations are welcome .
This battery was manufactured Jan 11th

I may install the old battery tomorrow just to verify
 
dirty connections? at the battery and at the meter.

how are the cables?
 
I wire brushed the battery leads, I'll hit em" again when I get back to the hanger..

Kyleb, thanks for the link, the mystery to me is why did it start with a new battery? the only thing different from the last time flown with a steady meter and this trip is a brand new battery..

the joys of plane ownership..:(
 
Certainly could be any one or more of the associated connections, but Dr. Bruce may be on the right track. Simply changing the battery would seem to point to the battery cables/connectors as prime suspects.
I think your 140 originally had the weird "pass through" ground strap connector, through the wall of the battery box, that, and the strap itself, can deteriorate with age. It might be time to consider Bogert's mod and cable upgrade(s):
Battery Box Mod STC SA4008NM – Bogert Aviation
(just a guess)
 
Jim Carpenter said:
Simply changing the battery would seem to point to the battery cables/connectors as prime suspects.
Click to expand...
Yep, mines a late model, 1975 so it has a different style battery box, cables were upgraded years ago (remember reading that in the logs).
"Start with the last thing you replaced."..It won't take long to switch the battery back out, I need to verify if it is indeed because of the new battery...doubt it but it would be a strange coincidence if its not.
Pipers are notorious for the "windshield wiper" load meter.
Anyone have any test routines for the whole charging circuits, ohm readings/voltage drops? Resistance through the main and alt switch seems to be one of the main causes.
She quit charging last summer and the little diode/resistor pack had broke a lead( votage to the field winding source ) . replaced that and the voltage regulator at that time. Piper didnt design these things for old fat guys to work under the panel!! I did clean all the battery connections ( both ends) while I was working on that.
Points to ponder
1. Didnt do it with the old battery....stick it back in and verify
2.The voltage is rock steady, 14.1..regardless of the fluctuating laod meter. Not sure what that means..

Thanks all..one upside...wifes out of town for a few days :)..more time allotment!
 
Murph said:
Anyone have any test routines for the whole charging circuits, ohm readings/voltage drops?
Click to expand...
First determine if it is an indicating problem. With a meter in amps, see if the alternator load is actually fluctuating or see if the regulator field voltage is fluctuating. Or a simpler check is with it running put an electrical load on and see if the affects the needle. However the 1st two check are more accurate and be sure to note the amp limit of your meter or get a meter that can measure above the system amp limits.
 
206,
I shut off all the avionics yesterday, one at a time, no changes..even when they were all off...still the swinging needle. Been texting my avionics guy this morning, he mentioned new batterys have more resistance than older batteries, so it may be just enough added resistance to start the Piper wiggle, with there being some corrosion being in connections/switches..exc. He did mention the voltage meter I was using may not have the sampling rate needed to catch fluctuations..I'm checking around to see if any friends have a meter with a graph...
 
Murph said:
I shut off all the avionics yesterday,
Click to expand...
Avionics do not provide a good load. Turn on landing/taxi lites, pitot heater, A/C, if you got it and see what happens.
Murph said:
new batterys have more resistance than older batteries,
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Given the ideal internal resistance of a battery is 0 ohms doubtful. And if there was resistance then you would also see a voltage drop and the battery get hot.
Murph said:
voltage meter I was using may not have the sampling rate needed to catch fluctuations.
Click to expand...
How wide are the needle swings in amps? Regardless, check the field voltage at the regulator and see if it is fluctuating as that is what tells the alternator to make more power. If the field voltage is steady, the charging voltage is steady there is 99.9% chance you have an issue in the ammeter circuit, i.e, indicating problem. I'll see if I can find a diagram for you....
 
206, Did use the landing light, strobes and fuel pump...didnt the pit tube heat though..this meter runs from 0 to 60 and its hitting 40. The diagram I have is extremely hard to make out the details..the SN of the plane is 28-7625022

Thanks again!
 
Murph said:
The diagram I have is extremely hard to make out the details.
Click to expand...
I can't get links to post but just google "Piper PA28-140 maintenance manual' and pick one. The electrical diagrams are at the end.

I take it this is a "loadmeter" with only the positive scale? And the needle swings from 0 to 40a on a steady rhythm? It doesn't appear there is an external shunt... is the alternator out cable connected directly to the meter then to the CB?
 
Have had this issue a few times as well ('67 PA28-140). Lots of good trouble shooting advice above. In my case, one time it was a bad voltage regulator. All the other times it was a loose/corroded connection somewhere in the circuit. Best I can tell you is to start by checking, cleaning and re-installing all the connections you can find. Last time this happened, I probably cleaned and re-tightened 20 different connections between the alternator and the battery. Don't know which one was the problem, but the "dancing ammeter" problem did go away. Of interest, while doing the checking/cleaning, did notice that the master switch was just a bit loose. Not enough to notice when turning it on/off, but it certainly could slightly rotate with a minor effort. Guess it is possible that with engine vibration, there could have been intermittent shorting. Troubleshooting this is tedious and time consuming, good luck.
 
An easy check of the health of the grounding strap and its connections: take a single jumper cable, and jump from somewhere on the engine to the negative battery terminal. NOTE! This assumes a negative ground system, which I think all planes are…. But if you have a rare positive ground system, following the above procedure will get kinda exciting …. in a bad sort of way.

OK once the above is done run the engine, flip on the alt or gen switch, and see if the load meter needle still vibrates. If yes, investigate every connection between the battery negative terminal and the engine block.

-Skip
 
My one time with an excessively oscillating meter was due to a bad master switch.
 
You don't just have just the new battery, you have the act of disconnecting and reconnecting. I'd be suspicious of the movement exacerbating a loose or poor connection somewhere that pulling on the batt cable might have caused.
 
Murph said:
206,
He did mention the voltage meter I was using may not have the sampling rate needed to catch fluctuations..I'm checking around to see if any friends have a meter with a graph...
Click to expand...
Digital meters are poor troubleshooting tools where there is a rapidly varying voltage or resistance or current. I use the analog meter that I bought 50 years ago. Its needle tells me everything I want to know.

Digital meters are cool. I have several. But they're common because they're easy to read and because they're cheaper to make so they sell for less. Electromechanical movements take time to assemble, by hand.
 
Bell206 said:
then to the CB
Click to expand...
CB?

Thanks guys, I took off every connection I could, wire brushed them (with a copper brush) cleaned them with contact cleaner, but it back together and it still did it. Removed the new battery, put the old one back in.....the meter does not fluctuate after you get above 1200 rpm, each addition of an electrical component steps the load dial up...fully loaded with everything on it pulls 35 amps..

Gave my 40 year old Simpson 260-8 meter to my son last year..

Dropped the battery off at my A&Ps shop, hes going to follow a drain/recharge procedure sent from Gills
I was wrong on my old battery, its been in my plane since 2016! Made Feb of that year!

Still cranks the Indian!
 
Bob Noel said:
My one time with an excessively oscillating meter was due to a bad master switch.
Click to expand...

Same here when I had a galloping alternator on my RV-6. I replaced the Cessna style split master and the problem was gone.
 
Murph said:
CB?
Click to expand...
circuit breaker.
Murph said:
hes going to follow a drain/recharge procedure sent from Gills
Click to expand...
What are the static voltage levels of the new and old battery? While its not common, your new battery may have a static charge high enough where the charging system doesn't know what to do? Checking your alt field volts/amps should show you this.
 
What kind of voltage regulator...built in...external mechanical ...external solid state ?
 
206.. 13.1 on the new 13.3 on the old this is read with a Fluke 325 so Id say its accurate. I need a helper to go any further.

Doug External solid state...under the panel..up in a corner,,in a space selected by someone with questionable parentage.
 
Double E probably..


ackkkkackkkack :D:D

Personally, I think they cut the wires too short and rather than admit it they said" oh no, we meant for it to go there"
 
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Who decided we needed a week for that?...L....
 
Murph said:
Who decided we needed a week for that?
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Wait for it...takes a "normal" person a day to celebrate an important event... but I guess it takes an e-n-g-i-n-e-e-r six more days to figure it out....:cornut:
 
the flip side is that we engineers don't get a month to celebrate.
 
Well it will be a day or four before I hear from my A&P, I'm really curious to see what the results will be.

Bob, where did you get your switch from?
 
Murph said:
Well it will be a day or four before I hear from my A&P, I'm really curious to see what the results will be.

Bob, where did you get your switch from?
Click to expand...

If you are asking me, sorry, I don't remember... it was quite some time ago. It might have been from Chief, or Spruce, or a local Piper supplier. Sorry I couldn't be more help.
 
Quite a procedure for the battery! Looking like its going to be about a 48 hour ordeal before we know something.
 
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