alternator dischare warning lights
 

I have had the rear engine alterntor discharge light flickering during flight.It seems to be only on light loads.My engineer says that its a common problem.The alternators seem to be charging correctly.When a heavier load is put on ie.Pitot heat then the light goes out.Has anyone experienced the same problem?

C337

I'm not an expert, and others may want to add to this, but I understand that the regulator(s) balance the load between the alternators. The service manual (your mechanic has one for your aircraft, right?) has clear instructions on adjusting the system for proper balancing. I don't think that you are at risk of damaging anything running a moderately unbalanced system, but it would be a good idea to do the adjustment soon.

One of the most knowledgeable contributors to this Message Board in this technical area is not too far from you, Pete Somers in Yorkshire, UK.

Ernie

had the sme problem for a long time and over time it became worse. my problem was in the printed circuit board componets started to go bad, (fuse holders, ect along with the borad being cracked) started to make one cycling until it sheared the alt coupling

Simple Things First
 

Stefan, Save time and money and try the following simple things first to see if the problem is either the regulator or fuse.

1, Since it is the front engine Alt. light that is the problem, switch the regulator from the rear engine to the front and take the front regulator and put it on the rear. If the flickering travels with the regulator you know it is that regulator. Don't know about the old regulators but the newer units are adjustable.

2, On the pilot side firewall, you will see two fuses. Take the fuses out and clean the saddles they sit in of all crude and replace.

Good Luck
Jerry
N34EC

Stefan,

I agree with Jerry's number 2 item (fuses), but respectfully disagree with number 1. I have had this problem a number of times, I think that Ernie's advice was correct. Adjusting the regulators is very easy, and is, I think, the most likely solution. I would do that first. The regulators don't fail very often, but they do get out of adjustment.

Also, it is important that your mechanic adjust them under your typical load. The electrical system on this airplane must have been designed by an intern, and as the wiring and components get old and resistance gets higher, it is common to adjust the regulators for one load level and have them work fine at that level, but have them display the behavior you described for another load level.

You and your mechanic can take your pick from the advice, obviously there is more than one way to skin this cat.

Kevin

Stefan

What you need to first is run the rear engine and load the alternator as much as you can and see that it will deliver the max current, ehile measuring the voltage, make sure it keeps around 27.5. However due to the long run of the wiring from the rear eng the voltage is never stable.
How many hours has the alternator done, when was the last time the brushes were checked?


Also check the condition of the wiring to the alternator, even the ring tags get loose on the wire.

As the previous posts, it is very common on this system to have either alternator 'coast' due to load loads and the battery being fully charged, and lalt out lights flickering.

The regulator system on the 'C' model is one regulator for both alternators and a REG1-REG2 switch in the panel ensures that you have a alternate.
There is no balancing system on this system, it relies on good maintenance of the system.

Regards
Pete Somers

Oh duh, you are right Pete, I forgot completely about the early models only using one regulator. Sorry Stefan, forget what I wrote about balancing...

Kevin

Keven!
I had to go back to the service manual to confirm the system, to far back in time to remember, brain getting tired!!

See you
Pete

many thanks everyone for this information.It has been extemely useful

In this thread, Ernie Martin mentions Pete Somers. Well, I've known Pete for over twenty years during which time he has always "fixed" all the usual electrical, autopilot and Cessna radio gremlins on my 337. He is really experienced having worked for Northair who wre the largest Cessna dealers in Europe. Sadly, they got taken over and all the "old hands" were made reduntant.
However, Pete still looks after "GH" and is coming down to Biarritz to fix the autopilot next month.
I notice that Pete often offers advice on this site, so all take notice. He really knows his "337s".
Thanks Pete.
Sunnysky.

Pete's expertise was evident from his contributions to this forum. We're lucky to have him. Wish he was on this side of the pond.

Ernie

Hey Ernie
Do'nt give me ideas. I may take you up on that one!!

Maybe it would be simpler to drain that "little pond" and build a few refueling stops along the way!