Electrical problem SOLVED!

[cessnadriver]

TO Dr. Dave.....
Doc I completed the 8 gauge wiring from rear starter to front starter and down to the negative post of the battery. Well you were RIGHT!! My amperage ran about 28.5 volts during flight. Afterwards the voltage rose to 29.5 volts which caused my G4 insight voltage reading to turn red-over volt! I checked the voltage regulator and saw that someone had increased the adjustment two notches to the "+" side, I turned it back to the neutral position, but haven't flown it since. I'll let you know how this adjustment goes. I purchased the four switches you mentioned, Battery, Alternators, Stand-by and Regulators but haven't installed them yet, probably in the spring. Also I received a Zeftronics ACU for Christmas and will be installing that in the next few days!
MANY THANKS FOR YOUR HELP!
BILLS

[DrDave]

BillS:

I'm glad the electrons are flowing in the right direction. Unfortunately I do not remember the background of the original problem. A little refresher would be great.

Dave

[DrDave]

BILLS:

I've dug through our last full year of posts. We covered quite a bit. Bring me up to date on the items that you've upgraded. It looks like you were planning on a panel change as well. I still have the templates and some spare pieces to assemble another panel.

To date have you only added the additional ground/bonding wiring?

Pictures help.

Dave

[cessnadriver]

Dr. Dave. I did the 8 gauge ground wire, which improved the charging system. I purchased a Zeftronics ACU for the #2 position of the voltage regulator selector switch, this is the down position. I adjusted the voltage regulator, which was allowing an over-charge, 29.5 volt. During a flight to Nashville, TN I had to shut down the rear alternator to get the voltage below the 29.5 voltage. Now with the ACU and the adjusted VR the system voltage is a STEADY 27.4 volts. The other thing I've discovered was how to remove the mount around the four switches, MASTER, ALTERNATOR SELECTOR, STAND-BY RUN, and VR SELECTOR. I'll replace them as soon as the weather is warmer, my hangar is NOT heated! So Dave that's it for now. Appreciate IT!! Also I'm not sure about changing the old circuit breakers? I would have to completely remove all the old C/Bs (non-resettable) with re-settable type. I haven't had any problems with the old type--MAYBE in the future??

[DrDave]

Thank you for the update. Good job on the auxiliary ground wire. That addition accomplishes three things. It now provides a solid ground path for the starter, alternator charging, and field wire circuit. You mentioned that the charge voltage is now set at 27.4 volts. That charge voltage is too low. I would like to see you charging around 28.8v in moderate to cool weather. There are some regulators that were set for a low charge voltage. That technology is long-since outdated. All battery manufacturers now recommend a much higher charge voltage. At 27.4v you are only getting a ~70% charge of your battery.

Replacing the flush, non-pull type breakers is really not that scary. I'll bet we have a similar configurations. If you remove the little screws that hold the circuit panel in you will see that behind the plastic overlay is a thin metal backing piece that the breakers go through. We replace that piece and mount the new breakers to it. The entire mock-up can be done without interrupting your current configuration. Once you have the whole thing built you transfer the faceplate over and hook up the wires to the new breakers. I would walk you through the whole process. The cool part is that I have the template for the sub-panel.

Back to the current project. I would encourage you to replace the field wiring to both alternators. I used 14 gauge to keep the resistance low. In the spring you can do all the related switches.

Sounds like a fun project.

Dave

[cessnadriver]

Dr. Dave. Thanks for the reply. The newer C337s have a charging voltage of the mentioned 28.7. But mine C337 is a 1965 the maint. manual calls for 27.7 voltage. So when I contacted Zeftronics they said that was the ACU approved in their STC list? So I went with that one. DO I HAVE TO CHANGE TO THE HIGH VOLTAGE ACU? What about the STC approval?? I'll change the field wiring when I replace the switches. I do have another parts C337 that I could swap the circuit breaker panel, I didn't think of that! Although I did try to remove a couple of old C/Bs once and the screws attaching wires are REALLY tight and the screws are NOT very good quality. But you're right I should do the swap. QUESTION: The odd 8 AMP size in the panel are hard to find any chance I could replace them with the modern 7 1/2 AMP?? MANY THANKS. BILLS

[DrDave]

BILLS:

The regulator choice is up to you. The original 27.7 was installed over 50 years ago. Battery technology has certainly changed since that was written. Gill and Concorde both recommend much higher charge voltages for their batteries. I will tell you that 1.0v difference is significant. Everything I do gets 14.4/28.8. Nobody considers those to be high voltages. They are the norm throughout all "12/24" applications.

The 8 amp breakers are no longer available. The current 7.5's are the correct replacement. The original breakers have a huge variance in their ratings. That 8 amp breaker may trip between 5-15 amps. I find they work best in the garbage can.

I will be eager to follow your updating process. Below is the start of another project.

Dave

[DrDave]

Originally Posted by cessnadriver

Dr. Dave. Thanks for the reply. The newer C337s have a charging voltage of the mentioned 28.7. But mine C337 is a 1965 the maint. manual calls for 27.7 voltage. So when I contacted Zeftronics they said that was the ACU approved in their STC list? So I went with that one. DO I HAVE TO CHANGE TO THE HIGH VOLTAGE ACU? What about the STC approval?? I'll change the field wiring when I replace the switches. I do have another parts C337 that I could swap the circuit breaker panel, I didn't think of that! Although I did try to remove a couple of old C/Bs once and the screws attaching wires are REALLY tight and the screws are NOT very good quality. But you're right I should do the swap. QUESTION: The odd 8 AMP size in the panel are hard to find any chance I could replace them with the modern 7 1/2 AMP?? MANY THANKS. BILLS

BILLS:

A more complete answer would be that the battery installed in your plane in 1965 was a flooded lead-acid battery. In comparison to a Concorde sealed battery of today the charge voltage was about 0.6v lower than the specified charge voltages of the newer batteries. Running the older, lower voltage regulator will maintain the battery in an undercharged state. For best longevity the higher charge voltage of 28.5-29.0v is ideal in the 32-59 degree temperature range. Those numbers come from the Concorde manual. Since the manual is copyrighted I couldn't simply copy it.

Dave

[rmorris]

Dr Dave/ Bills,

Read through your posts on electrical issues and solutions. Thinking i might run a 8ga ground wire back to front like you.
On related issue: there is a pkg deal offered in the parts for sale area of this site talking about upgrading vr to 400 series and placing in parallel. Any thoughts on that option v your zeftronucs acu option?

[DrDave]

Are we talking about a G model here? Those run two separate regulators with a common battery and parallel the regulators. The Zeftronics or the Plane Power regulators would be a good upgrade.

Dave

[rmorris]

no, talking about a T337C model... if you look at the parts for sale area of 337skymaster.com, you'll see an offer to upgrade, via field approval, to the 400 series regulators in parralel... looks interesting, like your opinion

[rmorris]

Did you buy cessna new switches for the madter, alt/vr, etc? If not, what vendor source and p/n did you use?

Originally Posted by cessnadriver

TO Dr. Dave.....
Doc I completed the 8 gauge wiring from rear starter to front starter and down to the negative post of the battery. Well you were RIGHT!! My amperage ran about 28.5 volts during flight. Afterwards the voltage rose to 29.5 volts which caused my G4 insight voltage reading to turn red-over volt! I checked the voltage regulator and saw that someone had increased the adjustment two notches to the "+" side, I turned it back to the neutral position, but haven't flown it since. I'll let you know how this adjustment goes. I purchased the four switches you mentioned, Battery, Alternators, Stand-by and Regulators but haven't installed them yet, probably in the spring. Also I received a Zeftronics ACU for Christmas and will be installing that in the next few days!
MANY THANKS FOR YOUR HELP!
BILLS

[cessnadriver]

rmorris. YES Cessna OEM! Sources: Preferred Airparts, in Ohio., Also used Ebay, ALL NEW/NOS (new surplus). I bought all for switches for $200. Where Cessna wanted $200 for just one! Parts like these are out there you just have to search. I used the part numbers from the Skymaster Parts Manual.
Hope this helps.
Regards, BILLS

[DrDave]

I got all of them from Cessna. The numbers from the parts manual have all been superseded. I think they had all but one of the switches I needed.

Dave

[cessnadriver]

Dr. Dave.
Yes I know that most switches have changed Part Numbers, but ordering from places like, Preferred Airparts and Ebay the original part numbers are generally still available. I think one of the switches I purchased was an alternate part number.
BILLS