The International Cessna^® 170 Association

Just got back from flying and my generator and/or voltage regulator was not working. The ammeter strictly showed a discharge with electrical load. Any ideas how to go about figuring out what the problem is? I flew two days ago with no problems, including night time.

George posted some good diagnostic info a few days ago,but I don't recall what thread it was on.

Eric

Bill,I found the info George posted. Look in the "hangar" forum,click on "delco generator-page 2". One post about testing generator,one about testing regulator.
let us know what ya find.

Eric

A couple of years ago, I had a regulator problem. The regulator would not stay in alignment. One of the screws that adjusts the gen cut in contacts would not stay set, and the generator would not charge. A careful look revealed that the screw seat, that metal tab that the screw sets in had cracked. The only difference I was told between an aricraft generator regulator and one off a 50's vintage car was the cover, even the bolt holes are the same. Just keep the cover off the old one and put in an overhauled or otherwise identical part.

Anyway I ended up replacing the the old analog regulator with a solid state one from Ziftronics (sp). The soild state one has worked very well even the noise in the radio's went away. No need to clean contacts and adjust voltage set points. It also has an option for a generator failure light that doubles as a "Hey you left the master swtich on" idiot light.

I believe they are slightly less expensive than the certified analog version and can be ordered from Aircraft Spruce. (~$125.00)

A simple test of your generator on the airplane is to clip a jumper onto the small terminal of the generator and ground the other end. If the generator produces current above 1400 rpm, then the problem is not the generator,...it's elsewhere....like the regulator, wiring, or master switch.
Be careful of that Prop!!

I was doing some circuit testing to see if I could figure out this problem of no charge--my generator was rebuilt 2 years ago and I don't think it would be the problem. Anyway, I accidentally blew the generator fuse. It is a Buss AGS-25. I pulled out my spare fuses and they were AGC sizes, not AGS. The AGC is slightly smaller in diameter than the AGS. I checked the hardware stores, auto parts stores, Radio Shack, Aircraft Spruce, Wicks, Chief, and a dozen electrical supply websites and I couldn't find AGS size fuses. Anyone run into this before? Any ideas? I can't troubleshoot any more until I replace this fuse.

I wouldn't assume that the Generator is good just because it was recently overhauled. If it was brand new it could still be bad. Poor Quality Control on the part of the manufacturer is a possibility.

Kelly

As an emergency measure - the smaller fuse will fit inside the metal caps of the larger fuse when you clean the glass out - it could be used this way till you come across some of the other fuses.

If the AGS fuses are so hard to find,& the AGC's are not easily substituted,it might be a good idea to change the fuse-holders to AGC models.Or to convert to circuit-breakers,that's what my 170 has. I like the pull-off,push-on type.

Eric

I had the same problem. Then I looked at some of the other fuses in my panel...and many were indeed the "too small" AGC type. Univair has the AGS size fuses...but are a bit pricey. Along with my avioics install in the next couple of months, I am going to replace all my fuses with breaker and end this hassle once and for all.

I would definitely advise you to use the "push-pull" style breakers, instead of the cheaper "pop-out" type. They're a little more,but I think they're worth it. When my 170 was converted to C-B's by a previous owner,he only used a couple push-pull types,most were pop-outs. I'm gonna change the cheapie's out one of these days. In an electrical emergency,you could pull all the breakers off & hopefully stop the fire/smoke/whatever in time.

Eric

I talked with a gentleman who is an electrical systems guru--he said the AGS style fuses are discontinued, though there are a few locations that still sell them. I'll pass those on when I get it. I'll check Univair too. The long term fix is to put the circuit breakers in, but I'll have to slide it in at an appropriate place on the priority list. Too long a list, too little money and time!!

Univair did have all the fuses I needed, although pricey. I also found them at Hi-line, http://www.hi-line.com, although they weren't priced there and not sold individually. I looked at a couple other suppliers, but the fuses weren't listed on their web sites. I ordered from Univair and will continue troubleshooting when they arrive.

GOOD IDEA Eric! Had never thought of it before, but all the commercial aircraft use the breakers that allow you to pull them out and isolate problems long before the problem gets bad enough to pop the breaker out. Would also allow you to fly with the particular circuit isolated until you reach a location where repairs can be made. I'll be looking for these...as I was going to go the cheapie "popout only" route!

Here is a source of many sizes and types of fuses with a lot of difinitions and other useful information. Many other products - clamps, etc.

http://www.mcmaster.com/