Electrical Failure on Take Off
 

I just flew up to Albany yesterday and had a power failure. I
had not flown for a number of weeks and the battery was low when I started engines at home base. I flew to Lake George and landed. On restart battery was back up to full charge. I then flew on to Albany. When I started engines again all was fine. I returned to Lake George and landed. On starting engines all was fine. I took off, pulled up landing gear. Gear went in fine, doors closed and I got a green light. Still in climb mode with full power on. All instruments went dead. Lost all electrical power, and both 30 Amp breakers poped. I turned off master switch and Alternator switches and pushed both circuit breakers in. I turned master and alternator switches back on and both breakers poped again. I leveled off at 3,500 feet and reduced power to 25 inches and props to 2,500 rpm. I once again checked all other breakers and I pulled out landing gear breaker since it happened when gear went up. I turned off master and alt. switches again. I waited about 3 minutes. I reset both 30 amp alt.breakers, turned on master and alt. switches. I had all the charge lights on. Front,Rear,Disc, and low voltage all on. I pressed alternator restart switch nothing happened. I was getting close to Albany,so I let them know I was having electrical problems I was working on. I flew north of their control area to stay clear and continued for another 20 minutes. Atc told me they were losing transponder. I started losing total battery power. At that time I tried again and this time I was able to get the alternators back on line. All the alternator error lights went out accept the alt.disc. light. The ammeter was showing a good charge all the way home.
This was a day flight with 50 mile visibility which is why I kept going. I also turned on my portable Garmin 295 and my handheld nav/com just in case I needed them. The mechanic did not look at problem yet. Any idea as to what happened.

Hi Dale
Sounds like you had fun and games?

1.Check behind the circuit breaker panel, make sure there is no signs of corrosion or damp.

2. Check the warning panel in the front engine bay, top firewall center and the diodes to make sure there is no corrosion.

3. I have had a HI/LO voltage sensor box fail, which put a Hi volts light on for a second or two, but this will automatically disable both alternators, we did find a circuit breaker poped, but put this down to FOD thru the rear alternator.
A replacement HI/LO sensor cured this problem.

If the gear motor caused the problem you would have noticed the high discharge on the ampmeter.

See how you get on and let me know.

Regards
Pete

three years ago mind did the same thing. after t/o the starter cylnoid stuck on and burned up the starter, boiled the battery and a complete electrical failure, had to pump the gear down. replaced the starter, battery and the cylnoid. mine is a 73p and none of the cylnoids have ever been replaced, after that i changes all three and have never had a problem with them sence. these cylnoids as they get old start to stick, they are only 30.00 and very easy to chang out. also sometimes the alt circuit board get old, corrorded and can even crack with will cause intermittent elect. problems, wear down the batt give gear problems and finally break the alt coulp, had that happen too. this fleet is really starting to age so don't be supprised what can crop up.

Electrical Power Failure
 

In the last 2 years, I have replaced all the solinoids on fire wall, new battery, all the diodes on fire wall, replaced the old voltage regulators to the new parallel system, replaced both alternator couplings, installed both new alternators and one starter also new motor on landing gear power pack. along with many other parts. This plane has always been hangered, so shows no corrosion anywhere. Total time airframe 2800hr., total time re-built engines 950hr. Dale

Sounds like you have covered most items.

Have you still got a DIS light on even though both alternators are ok now?

If you have the the HI/LO sensor is u/s

Pete

Electrical Power Failure
 

Yes, I still have the red disc. light on. Dale

Where are the Diodes, and what do they do?
Mine is overcharging, I suspected that the regulators are gone, the rear one was, and now the front one seems to be.
Could it be diodes?

Dale:

On my aircraft, the red light is "over voltage", not discharge. If you are getting an overvoltage condtion, it will trip the alternators off line. I would first check the output of each alternator with a voltmeter, one at a time. I would also check the diodes (both the little signal diodes and the large power diodes) on the circuit board on the firewall. This is very easy to do with a volt meter as well. If any of the diodes are bad, you can replace them with identical components from Newark Electronics for a fraction of the price compared to Cessna.

Mark

Battery...
 

Dale,

When is the last time you thoroughly checked the battery, the cables and the connections at the studs? AND water level?

SkyKing

For the Dive Bomber...
 

Larry,

Diodes are rectifiers consisting of a semi-conductor crystal material... they convert alternating current (AC) into direct current (DC). Your airplane only uses DC, unless it has an inverter for supplying AC voltage to the electroluminescent panel, if so equipped.

There are different diodes for different things... and your 1969 bird is a whole lot different than my 77 P-model, so I won't go there. Maybe look into your Parts & Service Manual for the electrical stuff would be a good place to start.

SkyKing

Larry:

There are two types of diodes on the circuit board, located on the top center of the forward side of the front firewall. There are two large power diodes mounted on heat sinks in the center of the circuit board. There is one for each alternator. They act like check valves, making sure that current only flows out of the alternator. That way, if one alternator fails, the current from the other alternator will not feed back to the failed unit. There are also some small signal diodes on the circuit board. They act in such a way so as to determine whether the battery voltage is higher or lower than the voltage put out by the alternators. It is this circuitry which controls the illumination of the alternator discharge and battery discharge lights on the instrument panel. There are also two large capacitors mounted under the circuit board, and they tend to dry out and fail. All of these are components that are easy and cheap to replace.

Mark

A rectangular red warning light....
 

Dale,
My POH for a 77 say's the red light is an over voltage sensor any time electrical system voltage exceeds 32 volts. (section 7 page 7-41) states to turn the alternator switches on separately to see if one or the other (front or rear) is the faulty system. guy

Hi all
OK, if the RED HI light is on and you had an overvoltage, you would notice as some electrical equipment would fail, and a high indication on the ampmeter would be a clue.

However if the RED HI light is on all the time even when the engines are shut down, the HI/LO sensor is inop.

This unit is mounted on the port side of the center console, top above the HYD Power pack.

The big diodes-
They are wired into both alternator output and a reed relay is connected across the diode.
In normal operation the diode is forward conducting and the relay sees about a 1 volt drop across the diode and remains de-energized.
Should an alternator fail the votage drop across will be approximately equal to the buss voltage and the relay will energize and put a ALT OUT light on.

The HI/LO sensor is field repairable however, they do not cost all that much.

Hope this helps

Pete

Electrical Power Failure
 

HI GUY AND OTHERS,
I just ran up to hanger to check plane on lunch hour. Guy, you are right the red light is the over voltage light. The one that is now staying on is the DIS amber light. I started both engines on ramp and did some testing at 1500 rpm. I tried first one and then the other alternator switch on and both give the same output on ammeter. I turned everything off while keeping engines at 1500rpm and ammeter shows a good charge but the DIS light stays on all the time. I will go back saturday and pull cowling and check all diodes and solinoids with a VOM meter. I have found many problems in the past myself. Dale

Dale

If the DIS lite is on all the time, it still sounds like you have a HI/LO sensor u/s.

Unless there is a problem behind the warning panel.

Let us know if you find the problem.

Regards
Pete

dis light on gear switch
 

my 73p has ei volt/amp gauge. my dis remains on but amps chk ok. now i will chk the lights closer. its in annual. During the annual i had mechanic chk ohms on landing gear switch. and found it dropping out/intermittent. we will replace. occasional delay going up. i never hear electric gear motor and do not want to burn one up. J

Skymaster.
If you have a DIS light on, even when you have both alternators on line, you have a Sensor u/s, or you do have low volts?

Pete

not low voltage
 

not a volt or amp low . according to the digital gauge. the dis lite stays on but system is a ok. just a glitch. next couple week it will be in the hands of a new owner. It will be in the best condition known to 337's. this 73p has given me great pleasure and I want to hand it off in better shape than i found it, I traded it for a cheyenne 1 fuel hog.every time i fill the cheyenne i miss the recip. Should i sell the pa31t i would go back into the p337. J

watch the hot starts, a friend of mine just somked one eng on a chy#3 maybe 200k
really sucks when of do not pay attention on start, other than that it is piece of cake and pleasure to fly.

Electrical failure
 

I went back up to hanger on Saturday and pulled cowling. I removed battery cables and cleaned and also checked the battery. It looks like I have one cell that is weak. Battery is a little over 2 years old. I did notice it did not turn engines over that fast. I ordered a new battery. I hope that is my problem. I also checked all the diodes on firewall. They checked ok with ohm meter. Dale

Interesting! I learned a long time ago (40+ years) the first thing you do when transient electrical problems show up is to buy a new battery. It's the cheapest way to diagnose and fix funny electrical problems. (Of course, you may just be able to borrow a good battery first.)

Tomorrow April 6th...
 

It will be 53 years since I soloed... Electrical glitches, gremlins what ever.. sometimes they go away on there own and sometimes they don't.. Good luck Dale... guy

And lucky I guess, 30 years operating turbines.... no hot starts.

Damn . . . . I'm young!!!

Keven
________
Xxx Tube Video

Re: Tomorrow April 6th...
 

I guess some of us solo at a VERY YOUNG age, and then there are those of us who soloed late in life.

C'mon Larry. Don't spoil it for me. Let me believe I'm young.

Keven
________
Wendie 99

Electrical Power Failure
 

Keven ,
You are probably a lot younger than Guy or myself, but Guy and I had more years of fun flying the skies, right Guy. Buy the way I replaced my battery and it did not fix my Dis light problem. It must be the sensor. Where is that sensor, I hope not on that circuit board in the center console I just replaced 2 years ago. Dale

Keven, you are young. In fact, you are just a baby, a kid, a youngster, a yout.

A yout?

:-)

Kevin

My Cousin Vinny. :-)
"These two youts"

Now I feel better . . . .
 

Larry:

Shew . . . . Much better. And by the way, I typically wear a velvet tux in court exactly like the one he wore in the movie.

Keven
________
ANAL XXX

Can I get Allie Cat to fix my transmission?

Kevin

Hey, Hey, Hey there!!!
 

Kevin:

Is that a euphemism for what I think it is? You dirty, middle-aged man! I'll see to it that she has no part of your "transmission" in the Keys, thank you very much!

:)

Keven
________
CUMSHOT MOUTH

Darn.

Kevin

Electrical Power Failure on Take- off
 

I just got my 337H back from annual. The failure was the high-low
sensor that is mounted in the center console below the throttle quadrant. Thats why the DIS light would not go out. Dale Campbell

Thanks for the update Dale.

Kevin

There you go Dale,
Saw this problem on a 337G a while ago and the alternators going off line was more that likely caused by FOD going thru the rear alternator, caused a short inside the alternator for a second but enough time to cause a Hi volts which took out both alternators.
The rear 35A circuit breaker had popped and the HI/LO sensor had been damaged.
The circuit breaker was restored and the alternators ran fine, but the DIS light was on all the time. The HI/LO sensor was replaced and the system check out ok.

BTW a search of the rear engine bay was done nothing found, a look at the alternator turned up the same.

Glad to hear everything ok

Pete Somers

Can anyone please tell me where is the Hi/Low sensor located?

On a T337H they are located under the pedestal cover on the right side

Item 32 (upper left, Detail F) in this drawing of 1970-73 planes.

What make & model do you have?

My Skymaster is a 1974 model, s/n 1563.