Electrical problem 182S

[Paveslave53]

So I’m out of the country currently and one of my friends went to fly the airplane the other day and he taxi to get fuel no issue when he went to takeoff all electrical died with no indications prior. Brought it back to the hanger and went to put a meter on the battery and it was so hot he could barely touch it so he removed it from the airplane in case of thermal run away.Turns out the battery was bad/destroyed, OK replaced with a brand new Gill sealed battery.The next time he went to crank the airplane all the avionics everything came up fine after the install but when you turn the key all electrical dies.I have a small video but not sure how to upload it. I wonder if the start contact relay is stuck ? The battery shows full charge and has been on the Gill 24 volt minder the entire time. One last thing is when he went to install the battery it arched and fried the top two threads of the post. Loose ground somewhere ? Anyone seen this before ?

 

[Bell206]

when he went to install the battery it arched and fried the top two threads of the post.

Something is still connected or shorted to weld threads, like the start solenoid. FWIW: anytime you have a battery get hot it's best to have someone check the system before you throw another battery in so as not to damage the new one.

 

[Dan Thomas]

There was a related problem with those airplanes. It involved a short between the bus and the alternator contactor case inside the MCU. That MCU is the box right above the battery, and it contains the master contactor, aux power contactor, starter contactor, alternator contactor and the ACU. It's crowded in there and a short that arcs the battery when being connected is most likely in that box. The plastic cover has maybe four screws holding it (one underneath where it's hard to see and get at).

The Cessna SB on the bus/alternator contactor short: https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=43013

 

[Paveslave53]

So I had my friend change the Start contact relay and now when you turn the key the power doesn’t go out but the starter doesn’t engage.....hmmmm. Also the battery doesn’t short out any more when you connect it.

 

[Bell206]

So I had my friend change the Start contact relay and now when you turn the key the power doesn’t go out but the starter doesn’t engage.....hmmmm. Also the battery doesn’t short out any more when you connect it.

You may want to have your friend disconnect the battery and step back until you can get someone with experience to your electrical system. Sounds like there are additional issues now and any further use may damage more components if not done so already.

 

[Paveslave53]

Something doesn’t make sense. he did find a wire pulled out of the cannon plug on the current sensor and he was able to get the pin out and repair it. I have voltage at the external contact,bat contact, and starter contact when you turn on the master but when you turn the key no voltage comes out the contact. I mean it’s a possibility that I got a bad part out of stock I guess.Of course my skyTec starter is two weeks out of warranty.

 

[Randomskylane]

Aside from the issue at hand; do you have issues with Gil batteries? Seemed like we replaced one every year in the skylane but Concorde goes several no problem

 

[Paveslave53]

Aside from the issue at hand; do you have issues with Gil batteries? Seemed like we replaced one every year in the skylane but Concorde goes several no problem

In the 208 yes 100% I will never run a Gill they are complete trash compared to the Concorde we use. In the 182 My last Gill was 5 years old. I like the new mx free ones haven’t had any issues yet.

 

[Dan Thomas]

Something doesn’t make sense.

You need someone that can read the schematics and knows how to use a multimeter. Without that person you will waste more time and probably spend more money and maybe burn up more stuff or create a situation where it all goes dark in flight.

There are reasons aircraft mechanics are certified. The average dude has no idea how much stuff has to be studied to get that certificate. And I have also observed that the weakest area for most mechanics is electrical. It's not the easiest thing to understand. So, if you keep messing around blindly, you're going to end up with major problems. That schematic you posted is only one of many pages involved in that system.

 

[Paveslave53]

You need someone that can read the schematics and knows how to use a multimeter. Without that person you will waste more time and probably spend more money and maybe burn up more stuff or create a situation where it all goes dark in flight.

There are reasons aircraft mechanics are certified. The average dude has no idea how much stuff has to be studied to get that certificate. And I have also observed that the weakest area for most mechanics is electrical. It's not the easiest thing to understand. So, if you keep messing around blindly, you're going to end up with major problems. That schematic you posted is only one of many pages involved in that system.

I appreciate that, he is one of the best aircraft electricians I know, he is a better electrician then A&P by far,even though he is a certified A&P. He has built all the wiring for our 208s for our weapon systems and countermeasures on our aircraft for a decade. Before that we worked H-53s together. The fact that him and I also an A&P IA, with 20 years experience can’t figure it out is frustrating. You say many pages of diagrams but Cessna manuals are trash. There is something in the system that’s not posted in the manual. Has to be. It doesn’t help I’m 7,000 Miles away trying to troubleshoot over FaceTime.

 

[Bell206]

he is a better electrician then A&P by far,even though he is a certified A&P.

The fact that him and I also an A&P IA, with 20 years experience

In your initial posts you came across as two pilots, looking to get out of a bind on the cheap, especially with all the arcing and what not. That’s why I recommended, and probably Dan as well, to step back and get someone who can troubleshoot properly. We see this regularly and I for one am not going to help a guy dig their own hole any quicker. You would understand the same being an APIA.

Cessna manuals are trash. There is something in the system that’s not posted in the manual. Has to be.

If you were talking about the old manuals I may agree with you. But the newer Cessna manuals especially the electrical side are much better. Regardless, this is a simple system and doubtful anything is missing in the manual. Aside from some extra widgets the starting electrical system on the 100 series is basically unchanged for years.

If your buddy is as good with a VOM as you say he is, have him chase the applicable voltage to K1 and verify K2 ground on the start relay. Sounds like the relay solenoid is not energizing. Given your original problem may still exist, may want to isolate and verify each individual battery/start circuit first, especially since you were welding battery post threads initially.

 

[PaulMillner]

There was a related problem with those airplanes. It involved a short between the bus and the alternator contactor case inside the MCU. That MCU is the box right above the battery, and it contains the master contactor, aux power contactor, starter contactor, alternator contactor and the ACU. It's crowded in there and a short that arcs the battery when being connected is most likely in that box. The plastic cover has maybe four screws holding it (one underneath where it's hard to see and get at).

The Cessna SB on the bus/alternator contactor short: https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=43013

Are you sure the alternator has a contactor? What purpose does it serve?

Legacy Cessna designs had all the contactors you mention, but none for the alternator, since it's self limiting by design.

Paul

 

[Dan Thomas]

Are you sure the alternator has a contactor? What purpose does it serve?

Legacy Cessna designs had all the contactors you mention, but none for the alternator, since it's self limiting by design.

Paul

Hmmm. I thought I saw that he said it was a 182S, which is a restart airplane and has that alternator contactor. I went back and can't see that. However, he posted a picture of the MCU and the schematic for that section of the system, and it applies only to restart airplanes. Then he said it was a 24-volt battery, another confirmation.

So if it's a pre-1986 airplane he has all the wrong information.

 

[Bell206]

I went back and can't see that.

It's in the thread title.

 

[Paveslave53]

In your initial posts you came across as two pilots, looking to get out of a bind on the cheap, especially with all the arcing and what not. That’s why I recommended, and probably Dan as well, to step back and get someone who can troubleshoot properly. We see this regularly and I for one am not going to help a guy dig their own hole any quicker. You would understand the same being an APIA.

If you were talking about the old manuals I may agree with you. But the newer Cessna manuals especially the electrical side are much better. Regardless, this is a simple system and doubtful anything is missing in the manual. Aside from some extra widgets the starting electrical system on the 100 series is basically unchanged for years.

If your buddy is as good with a VOM as you say he is, have him chase the applicable voltage to K1 and verify K2 ground on the start relay. Sounds like the relay solenoid is not energizing. Given your original problem may still exist, may want to isolate and verify each individual battery/start circuit first, especially since you were welding battery post threads initially.

Yea I could see how I should have led with being an A&P that’s my bad.

 

[Paveslave53]

Hmmm. I thought I saw that he said it was a 182S, which is a restart airplane and has that alternator contactor. I went back and can't see that. However, he posted a picture of the MCU and the schematic for that section of the system, and it applies only to restart airplanes. Then he said it was a 24-volt battery, another confirmation.

So if it's a pre-1986 airplane he has all the wrong information.

It’s a 182S come on that would be pretty sad if I didn’t know what type of airplane I own. All the j box items and the box itself were built by Lamar and the contractors have all been replaced with different FSOs my friend just told me they had a problem with replacing a start contact on a 206 last year they went through 3 of them from stock. Apparently they were not sealed properly or something. I called Aero performance and they told me they had a bunch of bad ones from sky tech. We have been through everything twice and it’s sucks but it looks like I’m going to have to buy another contractor. I’m debating jumping the contractor we just installed to see if it turns over. They prob won’t give me my money. Ack because it’s an electrical item that was installed but we will see.

 

[Bell206]

but it looks like I’m going to have to buy another contractor.

If you have verified power through the relay solenoid then quite possible bad relay. But as an FYI, I've had more issues with that solenoid circuit than relay itself. On the older 100 series power for the starter solenoid would come from CBs not associated with the start system. For example, as I recall some models got power from the instrument light CB upstream of the start switch. I can't see where the 182S gets the solenoid power as it flows into a different diagram. Had one where that CB was popped but they blew it off since it didn't say "START." Other had wire issue where it showed continuity/power but wouldn't provide enough amps to pull the solenoid. Test light would be a quick check.

I’m debating jumping the contractor we just installed to see if it turns over.

FWIW: I kept an old Ford start relay around to smoke check a start system vs a new relay. With the test relay and the above check, you might be able to confirm the system does work before you install another relay.

 

[Dan Thomas]

It's in the thread title.

Yes. I just thought of that. Duh.

 

[Paveslave53]

If you have verified power through the relay solenoid then quite possible bad relay. But as an FYI, I've had more issues with that solenoid circuit than relay itself. On the older 100 series power for the starter solenoid would come from CBs not associated with the start system. For example, as I recall some models got power from the instrument light CB upstream of the start switch. I can't see where the 182S gets the solenoid power as it flows into a different diagram. Had one where that CB was popped but they blew it off since it didn't say "START." Other had wire issue where it showed continuity/power but wouldn't provide enough amps to pull the solenoid. Test light would be a quick check.

FWIW: I kept an old Ford start relay around to smoke check a start system vs a new relay. With the test relay and the above check, you might be able to confirm the system does work before you install another relay.

I would have done that the first time but it’s a 24v. Good news is you can still get them from auto zone if you need one. We haven’t had time to touch it in a while but maybe tomorrow we can get back to it. Been dealing with a Pt6 that needs to be changed that got hot started to 1230.

 

[Bell206]

I would have done that the first time but it’s a 24v.

FYI: a couple of resisters or a cheap 24-12v converter on the relay solenoid circuit will make it work with 24v. The contactor bar can still handle the 24v loads. It was troubleshooting some vintage 24v helicopter wire issues I first learned this trick and simply adapted it to 12v or 24v airplanes.

 

[PaulMillner]

Hmmm. I thought I saw that he said it was a 182S, which is a restart airplane and has that alternator contactor. I went back and can't see that. However, he posted a picture of the MCU and the schematic for that section of the system, and it applies only to restart airplanes. Then he said it was a 24-volt battery, another confirmation.

So if it's a pre-1986 airplane he has all the wrong information.

I guess I still don't know what purpose an alternator contactor serves...

 

[Bell206]

I guess I still don't know what purpose an alternator contactor serves...

It's my understanding in the post-1995 aircraft they redesigned the electrical system to handle the higher 28v/glass cockpit loads and automated some functions to protect those 28v/glass loads. Even though most previous ALT regulators had the same protections it still fell to the pilot to disconnect the ALT from the system at the 1/2 switch. The ALT relay/contactor provides the means for the ACU to disconnect the ALT from the system regardless of the 1/2 switch position.

 

[Dan Thomas]

I don't have the manuals here (retired), but I know that if a pair of diodes in the alternator failed and shorted, they could drain the battery pretty quick. In a glass-panel airplane that could be a big problem. The ACU could open the alternator contactor (which is in the output line, not the field) to stop the drain.

 

[Spring Ford]

it looks like I’m going to have to buy another contractor. I’m debating jumping the contractor we just installed to see if it turns over.

it looks like I’m going to have to buy another contractor.
Fair enough.

I’m debating jumping the contractor we just installed to see if it turns over.
Is that legal? If they are in a union it might get hard to handle.

 

[PaulMillner]

they redesigned the electrical system to handle the higher 28v/glass cockpit loads and automated some functions to protect those 28v/glass loads.

That seems odd... generally, electrical loads go down as we get rid of legacy avionics, even with the electronic displays. Replacing incandescent bulbs with LEDs reduces loads more. Hmmm.

Even though most previous ALT regulators had the same protections it still fell to the pilot to disconnect the ALT from the system at the 1/2 switch.

No, if the overvoltage tripped, it removed field voltage from the alternator, shutting it down... opening the alternator half of the master switch simply opened a redundant switch in that same field circuit. Once the OV tripped, no pilot action was required to stop the alternator from charging.

The ALT relay/contactor provides the means for the ACU to disconnect the ALT from the system regardless of the 1/2 switch position.

That may be true... but the alternator half of the master switch never did disconnect the alternator... it just powered it down. Not sure why disconnection is suddenly important?

 

[PaulMillner]

I don't have the manuals here (retired), but I know that if a pair of diodes in the alternator failed and shorted, they could drain the battery pretty quick. In a glass-panel airplane that could be a big problem. The ACU could open the alternator contactor (which is in the output line, not the field) to stop the drain.

If a diode (or two, simultaneous failures?) shorted, they would become fuses. With a couple hundred amps flowing through them, they'd soon become an open. But even if that didn't happen quickly, the 60 amp alternator breaker would open... so the battery wouldn't have time to drain.

That said... in 40 years of working around Cessna charging systems, I've never heard of a shorted (rather than open) alternator diode... much less one that tried to drain the battery. Curious design decision.

 

[Paveslave53]

This is so fun, spent 2 hours shooting all the wires(again) everything had power where it should no issue, turn on the master everything works fine. Got power to the ext contact, bat, and start solenoid, sweet…… hit the starter no workyyy. Ok fine, lights don’t dim everything is good, change out the solenoid hook up the battery power on hit the starter all the lights go out and voltage reads 1 volt..huuuu????? after checking it 5 times at 24V,Brand new Gill. Go to the back of the airplane and the battery has started swelling and off gassing by the time he could get it unhooked it was already 180+ in seconds. Crazy thing is it’s been in the airplane for a week with no issues. Time to start tearing out interior and inspection of all the cables by hand. I’m thinking the connection of the main terminal going to the ext. contact is shorting when you hook it up it reads fine because it just sits where it’s not shorted. But in the process of hooking it up it shorted somewhere resulting in reverse current to itself. In 20 years 3 of us have never ever seen that.

 

[Paveslave53]

it looks like I’m going to have to buy another contractor.
Fair enough.

I’m debating jumping the contractor we just installed to see if it turns over.
Is that legal? If they are in a union it might get hard to handle.

uhhhhh auto correct...legal don't think so but not 100%

 

[Bell206]

That seems odd... generally, electrical loads go down as we get rid of legacy avionics, even with the electronic displays. Replacing incandescent bulbs with LEDs reduces loads more. Hmmm.

In my experience it depends on the aircraft and what you change. The OPs 182S aside as noted below, I've seen aircraft lose load or gain load with newer electrical equipment installs. On the gain side it's usually due to more equipment function is installed than removed. Have run across a few legacy aircraft that failed their 80% ELA after certain "glass" upgrades due to that increased load with the original electrical system. But that issue is usually easy to fix in most cases but at an added cost.

Not sure why disconnection is suddenly important?

The certification requirements had changed once Cessna restarted production due to the increased use of electronic equipment in aircraft. A number of those changes were directly related to electronic displays and IFR requirements. Part of those changes further defined essential power requirements, system fail safes, and pilot load shedding capabilities. The simple move to comply with those requirements was to add contactors/relays and control units like the ACU and its associated contactor in the OPs 182. It's also the reason the post-95 aircraft are 24 volt as well to manage the larger electrical loads.

 

[Bell206]

I’m thinking the connection of the main terminal going to the ext. contact is shorting when you hook it up it reads fine because it just sits where it’s not shorted. But in the process of hooking it up it shorted somewhere resulting in reverse current to itself.

Don't quite follow this comment. Are you saying the external relay is shorting to ground once you connect the battery? Or has your starter failed internally and goes straight to ground? Have definitely seen that type of failure and it does pull the guts out of the battery. To get a battery to swell and "gas off" is one heck of a short. Perhaps ohm out/smoke check the starter separately? Another T/S method to check a start system is to rig up a GE4509 in place of the starter which might help to isolate the problem without leaking the rest of the system smoke out.

 

[Dan Thomas]

Ok fine, lights don’t dim everything is good, change out the solenoid hook up the battery power on hit the starter all the lights go out and voltage reads 1 volt..huuuu????? after checking it 5 times at 24V,Brand new Gill. Go to the back of the airplane and the battery has started swelling and off gassing by the time he could get it unhooked it was already 180+ in seconds.

That there tells me that someone has made a serious error in connecting the new contactor. Nothing happened when you hit the starter, so you changed the starter contactor. As soon as you hit the starter everything goes dark and the battery is somehow shorting to ground. Pulling the interior out and looking for some short along the cables is likely a big waste of time. The problem is probably in that MCU box, and that's what I'd be looking at. You might have miswired the thing and created a self-latching problem on a contactor so it won't release until the battery is disconnected, and it's big terminals are in turn miswired so it's grounding the power.

You need all the schematics for that box and you need to study them and trace EVERY connection and make sure it's right.

 

[mondtster]

Personally, I’d be getting a fresh set of eyes on the problem. Obviously something is getting overlooked.