alternator is NOT working

Mike Ice · #1 08-03-2008, 10:22 AM

Hello,

Just started the process to get the DAR out to the hangar next weekend. The last two weekends have been spent chasing and working out bugs.

Questions that I have.

I have the Aeroelectric set up for my electrical system. I don't have an amp meter, just Van's volt meter.

First.

I could not get the starter to work until I removed the diode from across the starter contactor. After I removed it the starter worked just fine. Do you think I just had the diode installed backwards?

Second.

I don't think the alternator (plane Power 60 amp) is charging the battery. The voltage on the volt meter reads very low and the charge in the battery keeps decreasing.

So. Do you think I may have the diode on the battery contactor installed backwards? Or. Does the alternator have to get up to a certain speed before it begins to work?

Thanks,

Mike Ice
Rv-9 soon to be an airplane.

Radomir · #2 08-03-2008, 10:39 AM

If your volts are reading anywhere in the 12.xV range, your alternator is not working properly... with engine running, even at idle, you should be reading more than 14V.. eg.. 14.4V is what I have..

I'd start off by making sure ALL the wiring is done correctly... do all continuity testing along with making sure that alternator is putting out 14+V ... (test that at output termina of alternator.. not somewhere way downstream).. There are quite a few possibilities here, so troubleshooting could take a while...

make sure alternator field is getting voltage and that correct wires on the connector are wired..

Mike Ice · #3 08-03-2008, 11:11 AM

Radomir,

Thanks for the post.

I thought of testing the alernator output but didn't want to get too close to the prop. I know attach some long leads would have been the answer but I was tired and not thinking clearly. That is a good place to start.

Mike

frankh · #4 08-03-2008, 11:30 AM

I would start at the alternator too.

Take your meter and like you suggested use test lead with a clip between the alternator B lead stud and the Battery negative terminal.

But first with the master on make sure you are getting battery volts at the plug on the back of the alt that powers the field winding.

I.e check the obvious first..

Frank

wjnmd · #5 08-03-2008, 02:35 PM

I'm having exactly the same problem. I have a 60 amp experimental Plane Power alternator wired using the Aero-Electric type wiring. I also have an alternator warning light as per the Plane Power schematic. I would find that when I am on the ground and during run-up it works great, shows a charge on the ammeter and shows 14.4 volts. About 10-15 minutes after takeoff the alternator warning light comes on and the 5 amp ATC style fuse has blown. I have configured my plane so I can get to the fuse block in flight if necessary with a drop down door. If I change the fuse in flight, it immediately blows.

I have checked my wiring for a short from the fuse block to the alternator field switch to the alternator and it all checks out with a voltmeter. I have been in touch Billy Jowers at Plane Power and he had several suggestions but nothing seems to work so I sent the alternator out to the Plane Power folks just a couple days ago. I'll let you know what they say.

There is an A&P at my airport and he says this pattern of failure (failure when the alternator is in flight when it has heated up) is characteristic of a voltage regulator problem. I have an alternator cooling tube as per Van's recommendation in the baffle plans so I don't think it's due to inadequate cooling. Billy says the Plane Power alternators usually cool very well so we'll have to find out.

I would suggest you wire in an alternator warning light. It's easy to install and will give a little better warning since bright red light will really get your attention.

Bill Near
RV-7A flying but still working out the bugs. What a fabulous airplane!
N811WJ

Mike Ice · #6 08-03-2008, 08:33 PM

Hello,

Well, perhaps I figured out what was causing my problem with the alternator that wasn't.

I do have the plane power alternator and the over/under voltage lights as suggested.

What I found today was a problem with the electrical plug in the back of the alternator. I found that no matter how hard I pushed in on it the darned thing would not go in and snap over the locking tab. It would go in and feel snug but after an engine run or a gentle tug it would come right out.

I discovered that the plug runs into a washer on a screw and this will not allow the plug to go all the way in. I took the back of the alternator apart and removed the screw (this screw has the washer as an integral part) and then filed part of the washer flat. I put it all abck together and the plug cleared the washer and snapped right in.

I started the engine and instantly got a voltage reading.

Bill, I hope I don't have the over heating problem your mentioning. I do have the cooling blast tubes and it doesn't really get all that hot here in Alaska.

Once I get the RV flying I will report if I have any further problems.

Thanks for every one's suggestions.

Mike