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  #1  
Old 07-27-20, 12:36 PM
frank.oconnor19 frank.oconnor19 is offline
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ALT restart batteries

Does anyone know where these are.
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  #2  
Old 07-27-20, 01:48 PM
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Location

Hi On my 73 G model they are behind the pedestal accesible from the pilots side. Move the seats back get on your hands and knees and look in behind. pretty easy to spot. Covered by a black plastic cover eay removable. Mine use 2 C batteries.
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  #3  
Old 07-27-20, 09:28 PM
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Alt. restart batteries

Gord is correct, they are located at the height level of the throttle quadrant behind the instrument panel half way to the firewall. My P337H has a holder that takes 4 c cells, I believe an Energizer battery, E-93. Cessna SIL ME79-5 references the Cessna Service Kit 337-46A and it explains the installation of the new updated version of the battery holder. From what I gather, there was initially a different sized battery to do this job, but the kit installs 4 C cells.
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  #4  
Old 07-31-20, 11:22 AM
frank.oconnor19 frank.oconnor19 is offline
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Found the holder and replaced the batteries. Thanks for the help.
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  #5  
Old 08-15-20, 11:29 AM
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missing battery pack?

I've been looking for awhile... I don't think the bird has a battery pack (it's supposed to have something) installed anymore. NA 77 G model. I'll post some photos--maybe you eagle-eyed folks can assist a sweaty seeker?

Symptoms: at low RPM, the batt DIS light occasionally flickers ON (normal)

Ammeter occasionally waves "hello" (normal) with a slow back and forth wave of small amplitude.

At 1000 RPM, system voltage is 26.8 to 25.2 (low and variable--not normal)
--caveat: this is only indicated on a combo voltage meter/USB charger stuffed into the cigar lighter hole--one man show so it's tough to check voltages with meter at alternator with engines running.

Neither ALT out light will illuminate (checked bulbs, light good) with Battery ON and ALT switches ON (engines not running). --not normal.

OVLT light will illuminate when button pressed (normal) but ALT restart button has no effect. (not normal).

REAR alt will carry the whole load, but shut off the rear and FRONT will also drop offline intermittently (not normal).

Bottom line? The system fails the check in the amplified normal procedures section of POH. It's not mentioned in the logs at all. Several entries about regulators, capacitors, alternators...nothing at all about alt restart circuit.

Cure?
1) fly day-VFR only until all indicators and switches work normally.

2) rebuild alt sensing circuit board and replace diodes, and find the dang battery pack & put new batteries in, then retest.

3) scrap it all and put in two new planepower R1224 regulators.

Thoughts?
Attached Images
File Type: jpg P side pedestal_sm.jpg (984.2 KB, 257 views)
File Type: jpg CP Side pedestal_sm.jpg (61.1 KB, 229 views)
File Type: jpg CP Side Pedestal_sm2.jpg (72.5 KB, 261 views)
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  #6  
Old 08-15-20, 08:02 PM
frank.oconnor19 frank.oconnor19 is offline
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Mine were on the pilot side. More towards the firewall so the picture was not too helpful. Except it may be the black box in the picture on the pilots side too left of the frame, hard to tell from this picture. On mine it was a black cap over the batteries secured with a wire tie.
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  #7  
Old 08-15-20, 09:07 PM
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Battery Pack

Mine is located right here, circled in the picture. Just forward of the shielded resistor on the same support the resistor is on.
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File Type: jpg P side pedestal_sm.jpg (318.4 KB, 246 views)
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  #8  
Old 08-16-20, 01:57 AM
DrDave DrDave is offline
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Learjetter:

Does the amp gauge needle stop waving at you when you are running on the rear alternator only?

Dave
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  #9  
Old 08-16-20, 01:36 PM
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DrDave--

I believe it does steady out when running on 1 alternator only. I'll double check next time I'm troubleshooting.

Assuming it does, what does that mean? Problem with the parallelling function of the circuit board, yes? I've been thinking I'll replace the components--having a challenge determining specs of the diodes, resistors and capacitors (old part numbers vs new-fangled website nomenclature, you know?)

TIA for any thoughts!

-J
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  #10  
Old 08-17-20, 01:51 AM
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Learjetter:

I've read through your symptom list. It appears that you have a couple of things in play here. I think we need to establish some baseline items here. I would like to make certain that the front alternator drive coupling is happy. Stick your finger in the fan of the front alternator and see if it turns past the point of medium resistance. We are ruling out that the two rubber pieces aren't mangled.

I'm concerned about the low voltage at 1000 rpm, even considering that it is being read by less than reliable means. Along that line I am curious about the front alternator that will "drop offline." By drop offline do you mean blow the field breaker? I would like to rule out a diode failure in the rectifier bridge. This is a simple test. With the front engine running and the front alternator online with a medium load read the millivolt AC output. Put your meter on the AC scale and select the lowest voltage setting. I'd like to see a number <50mv. You can do your measurement with your test-leads on the battery preferably.

If we pass those two tests we can dig in further to the fun stuff. I have the schematic for the G model. There is only one Alternator system drawing. Let me know what you find from the above two tests.

We will fix this.

Dave
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  #11  
Old 08-17-20, 09:45 AM
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For "one man show" alternator readings, may I suggest you run test leads to the battery from the multimeter that are long enough for you to pass them through the pilot port window, so you can start the engine and take your readings safely from the pilot's seat? You can test the voltage and the AC ripple that DrDave wants to know. Be sure your battery is fully charged before you perform the ripple test (measure AC voltage in a DC circuit). I would perform the tests with both alternators operating, and with each one individually.

Last edited by mshac : 08-17-20 at 09:57 AM.
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  #12  
Old 09-09-20, 12:43 AM
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Quote:
Originally Posted by DrDave View Post
Learjetter:

I've read through your symptom list. It appears that you have a couple of things in play here. I think we need to establish some baseline items here. I would like to make certain that the front alternator drive coupling is happy. Stick your finger in the fan of the front alternator and see if it turns past the point of medium resistance. We are ruling out that the two rubber pieces aren't mangled.

I'm concerned about the low voltage at 1000 rpm, even considering that it is being read by less than reliable means. Along that line I am curious about the front alternator that will "drop offline." By drop offline do you mean blow the field breaker? I would like to rule out a diode failure in the rectifier bridge. This is a simple test. With the front engine running and the front alternator online with a medium load read the millivolt AC output. Put your meter on the AC scale and select the lowest voltage setting. I'd like to see a number <50mv. You can do your measurement with your test-leads on the battery preferably.

If we pass those two tests we can dig in further to the fun stuff. I have the schematic for the G model. There is only one Alternator system drawing. Let me know what you find from the above two tests.

We will fix this.

Dave
DrDave,
Iíve replaced the old and unhealthy-looking diodes, relays, capacitors and resistors in the front firewall circuit board. Replaced warning annunciator assembly. Replaced some very shady and badly corroded contractors with Sky-tec (battery, starters, ground power). Alternators turned by hand meet resistance in less than 1/8 turn.

When running front engine only, was able to adjust Original Voltage regulator to 27.9v. Rear DGR5-1 VR appears to run at 26.5v. Together: 26.5v. Select either offline after both online, you get 26.5v. New battery voltage is 25.4, and DIS light comes on at 25.9v. All annunciations appear normal. Ammeter still intermittently waves slightly and rythymically Even when beacon off. Have not touched or adjusted overvolt/undervolt circuitry. There is no battery pack in the aircraft so Iíve labeled the ALT RESTART switch as INOP.

Iíll try to remember the AC volt test next session. Thanks for your thoughts.
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  #13  
Old 09-09-20, 12:58 AM
DrDave DrDave is offline
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Good evening:

You can't like any of that. It sounds like the front engine system is the closest to normal. I would adjust the front regulator to 28.4V. Once it's set there let's see how it handles the load. We also want to see a steady amp meter. If the amp meter is waving at you there is a problem in the field circuit. Let me know what you get and we will diagnose.

One step at a time will win the battle.

Report your findings.
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  #14  
Old 09-10-20, 07:57 AM
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Interesting and timely topic. I recently experienced a significant electrical event after takeoff; I thought I had documented it here but didn't and will add that topic today.

I wanted to mention that as the troubles were corrected, the amp meter continued to have a "hard, full-range cycle. On the ramp, I ran through the Electrical System Ops Check outlined in the POH, and at the end of the successful test, I realized that my amp meter indication had returned to the regular, light, small bumping on the meter.

My battery pack did not pass the Alternator Restart Test, so the batteries are being replaced now while the airplane is in maintenance. I found and purchased the SK337-46A Battery Pack Kit recently. Given what happened to my airplane, my mechanic might replace the existing pack with the kit.

As pilots, we are supposed to perform both the Electrical System Ops Test and Alternator Restart Test at 25-hour intervals. I remember this from attending Cessna Skymaster school in January '78. While in the airplane, the paragraph format in the Manual is tough to follow. I listed them out in checklist form in ForeFlight and also kept it as a document within the app (attached).

From experience, when you push on either electrical test button, push with a clockwise movement on the button. The button is thread onto the shaft of the switch, that shaft is free to rotate. It is impossible to get them too tight, but I have found them missing and on the airplane floor. I haven't experienced the loss since I started adding the rotation with the push.
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File Type: jpg SK337-46A.jpg (22.3 KB, 209 views)
Attached Files
File Type: pdf Electrical System Test Checklists_REV 1.pdf (24.0 KB, 205 views)
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  #15  
Old 09-10-20, 02:38 PM
DrDave DrDave is offline
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Does the regular, small, bumping of the amp meter correspond to any known electrical load?

Dave
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