Electrical Issue

How to keep the Cessna 170 flying and airworthy.

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170C
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Electrical Issue

Post by 170C »

Seems one problem gets solved and another pops up :( Started engine Sat morning. Didn't spin as fast as I like, but engine is easy starting one. Flew an hour to breakfast and battery wouldn't turn engine over. Propped it and flew back home. AMP meter showed good charge for a good 20 minutes and gradually came back to neutral, as it normally does. Let it set for 10-15 minutes and attempted to restart--barely moved the prop. Put battery on bench, hooked up battery minder and left until today (Mon). Battery shows proper amperage so took it to Auto Zone for a load test (portable load tester) using 224 cold cranking amps (forgot that it was an xc with 350 cranking amps). Test showed good. Went to O'Reilly's for same test. First testor was also a portable one-tested ok. Second test was wih a better testing unit in the store that can also charge the battery. Test showed battery ok.
I may have schewed the test by providing the incorrect cranking amps? Put battery back in plane and starter will just barely turn engine over. Could it most likely be a bad battery (3 yrs old last day of Aug) or maybe a grounding issue or a bad starter? I would like to ck the grounding first & would like suggestions what all to check. I have a refurbished/overhauled Delco/Remy starter I could install, but would rather save that option to last. Thoughts?
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Re: Electrical Issue

Post by MoonlightVFR »

When you find the answer you are going to be so happy.

Nothing disheartens as much as a slow slow moving prop at crank time.

You have proved battery is most likely fine.

What about the grounding? Your ground strap moves from the Bat down to a bolt that is intergal to the entire firewall.
Is that it? Do you have anymore strapping?

Answer is already posted elsewhere this website.

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gradyb, '54 B N2890C
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Bruce Fenstermacher
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Re: Electrical Issue

Post by Bruce Fenstermacher »

So this is a Concord RG XC-35? This battery usually lasts longer than 3 years. If it wasn't an RG I'd say your battery is shot.

So you took your aircraft battery, a recumbent gas matt aircraft battery at that, to two warehouse style auto motive parts stores where a highly trained maintenance technician who happens to be selling parts, used a tester, not likely to be compatible with your battery, to test the battery.

Then you charged the battery with a Battery Minder. Was the Battery Minder specified to work on a AGM battery?

Frank, what could go wrong here.

I ask this because a AGM or a wet cell lead acid battery such as the Gill G-35 is not a automotive battery. Aircraft batteries, wet cell at least use a heavier electrolyte. And so unless your tester was a manual tester and you adjusted your test for the exact formula of the battery, your test is likely in error or your charge was cut off prior to the battery being fully charged.

The most likely suspect here is the battery or the charging system. When the battery won't start the plane, try to jump the plane. Does the starter spin as it should? If yes it's not the starter.

Here is a great place to start:
Owners manual http://www.concordebattery.com/otherpdf ... manual.pdf
Continued Maintenance Manual http://www.concordebattery.com/otherpdf/5-0171.pdf

Notice on page 13 of the owners manual (first manual) is a simple test. After 4 hours from last charge in an open state (no load) your battery voltage should be 12.9v or higher. If not, the battery is not fully charged or is not capable of being fully charged if you've followed Concords charging instructions for the charge. See the second manual for the exact equipment required to charge and test the battery.

Have your battery charged by a aircraft mech who has half a chance of doing it correctly and then being able to test the capacity correctly. If it passes when you reinstall check your ground connections. For testing purposes I'd start the plane and run it till the engine cleared and shut it down and repeat. See how many starts you can get you feel confident with. You should get several starts. Your testing the batteries capacity under real life conditions. Fly the plane to recharge the battery and then test the batteries charge. Has the generator fully recharged the battery? If not still could be a battery issue but maybe the generating system such as a ground connection there.

Personally I'll bet you find your battery has died early in it's expected and will start a lawn tractor for years but not your airplane.
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edbooth
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Re: Electrical Issue

Post by edbooth »

Frank, do you have the old manual pull type starter ? If so, you may want to check the contacts on that starter switch. May have a burnt switch causing high resistance..... Just a thought. :?
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Re: Electrical Issue

Post by 170C »

I did check the contacts on that starter (it is still the pull type) and although pitted somewhat, it would appear they aren't burned. I am going to chase out the grounding possibility. Hoping that bolt (?) on the firewall doesn't have a nut on the cabin side that has to be secured in order to remove the grounding strap to be cleaned (it probably does). One suggestion was to ck the resistance between the battery negative post and the starter negative post while engaging the starter.
The battery is a RG-25XC Platinum, not a 35 and NO it wasn't charged by an "official" Concorde charger. I suspect there's probably not one on the airport unless its at the FBO. I have not known very many owners who have invested in aviation battery chargers due to the cost and most use automotive chargers with success. However, I will ck with the FBO and if they have one (probably do) I'll give that a try along with the other suggestions. I agree, a 3 yr old battery on a plane that is flown regularly shouldn't be failing. I appreciate input. Thanks guys!
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Re: Electrical Issue

Post by Bruce Fenstermacher »

Shouldn't be failing but I've seen it. At the cost of a new battery, finding a charger that is not an automotive automatic type. It doesn't have to say Concorde on it, just be a constant volt or amp, I forget which (consult the manual I linked) is worth eliminating the issue of knowing you did it by the book.
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Re: Electrical Issue

Post by MoonlightVFR »

When I pull the starter cable I want engine power within half a blade prop turn.

Original design for ground in C170 has got to be circa 1930s. Even when clean and tight its efficiency is poor.

Several folks have left orig ground strap connected to firewall but added an additional NAPA braided cable direct to
engine.

More details are in this forum
gradyb, '54 B N2890C
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Re: Electrical Issue

Post by c170b53 »

Moonlight wrote initially
When you find the answer you are going to be so happy.
Answer is already posted elsewhere this website!
This is a happy forum
.
For a bit there I thought possibly someone from China had hacked your 170 account.
After recent maintenance I pushed my master rocker switch to off, or so I thought I did. The switch was half way between on and off and unfortunately the T&B drained the battery flat. Haven't tried it yet but will report back if it survived.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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Re: Electrical Issue

Post by 170C »

Success ! 4 load tests, one at fbo, all showed battery ok. Suspected a possible ground issue. As above comment, some questioned validity of ground strap attached to firewall. Kept checking and quite by accident noticed the starter motor was loose. Removed starter and adapter and found 3 of the 4 screws that attach the motor to the adapter housing loose and 4th not properly torqued. No idea why these screws got loose. Tighten screws and applied power to starter and it spun up pretty well. Since I had a spare Delco-Remy starter that I had overhauled 2 yrs ago. Applied power to it and it appeared to spin faster so I installed it. I too will add another ground strap to supplement the one attached to the firewall. Starter now rotates engine as it should! Tomorrow it gets put to the test when I fly it.
Thanks to all for your suggestions.
I did find one disturbing thing as I checked vrs items. Discovered one of the thru bolts on the rear engine mount was loose-finger loose! Have no idea how or why this situation developed? Tightened bolt. Wondering if this could be a source of some of my oil leaks. Strange things seem to occur. Who would ever think to check engine mount bolts at annual or other inspections?
Frank
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Re: Electrical Issue

Post by GAHorn »

170C wrote:... Who would ever think to check engine mount bolts at annual or other inspections?
Frank
Item 21 on the 100 Hour/Annual Inspection Check list, Page 2-14 of the 100 Series Service Manual.

I liked Bruce's suggestion that you "jump" the aircraft to see if another battery produced the same defective results as your battery alone. Did you ever install that AN-2552 Ground Service Plug? I sure have found it handy. (Page 52, Fig 93 of the B-Model IPC.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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