The International Cessna^® 170 Association

I have been having battery discharge problems for the last couple of months. I had the voltage regulator taken off and had it tested at a local shop. They stated that they clean it and set up the voltage but recommed to replace it. I have tried a few calls from parts company in Trade-a-planes including Univair but am not having any luck finding one. I don't want to replace it with another vibrating points type, instead I am hoping that they make a solid state type. Can someone give me their 2 cents.

Larry

The Zeftronics solid-state units are very good. Spruce carries them, and there are other sources. http://www.zeftronics.com/

See also this item in the MX Library section of this forum:
http://cessna170.org/phpBB2/viewtopic.php?t=4854

John

Amp meter shows discharge when turning on electrical devices.

I have not been able to fix the problem. Heres what I done so far.

I have taken off the generator and had it tested and the shop says its okay. I have taken off the voltage Regulator and the shop says its fine.
I have taken off both the Gen and VR and taken them to the shop and they say they both work fine. I have seen this with my own eyes.

Problem:
When I ground the Fld on the Gen to the airframe it is suppose to give unlimited amps but my amps gauge in the plane show no increase even at 2000 rpms. I turn on devices and it shows discharge so the gauge seems to be working fine. I test the Gen with the FLD grounded with a amps tester and it shows about .5 amps at 1000 rpms. I don't feel comfortable having someone do a run up with me next to the propeller. I have polarized the REG according to directives in past forums so I don't think that is the problem. I changed the fuse even though the old one was okay. I have ordered a new REG but I think I am wasting my money.
I checked the wires from REG to VR and they are okay. So what do I do next? I don't have a wiring diagram for my 1953 170B. Any help is appreciated.

Larry

Larry,

George Horn, our moderator, is an expert on this stuff. He has published an electrical system service manual for the 170 that is available from the 170 association. Click on the "store" link on the association's home page, and scroll down about halfway to find it.

There's also a very good troubleshooting sheet at the Zeftronics web site. Go to http://www.zeftronics.com. Click on the "Troubleshooting" link on the left side of the page. Then click on "Delco-Remy" and "14 Volt Type A" links to get to it. This is a troubleshooting guide for generators and standard, vibrating-relay type regulators. Follow it, step-by-step, assuming nothing about where the problem might be.

Good luck!

John

I will give that a try. Please watch for a response from me. I like to be able to solve problems. Yes is would be easy just to take it to the FBO but its a learning thing. Thanks again

Larry

Larry,

Try grounding the field terminal of the generator through an ammeter to see if you're getting field current (use a 10 or 20 amp scale). If you aren't getting current and the generator checks good, then you aren't getting power to the battery terminal of the generator. Check the voltage at the battery terminal with and without the field grounded. If the batt terminal voltage drops way down when you ground the field, then you have high resistance in the armature circuit. That could be a broken or corroded connection any where from the battery to the bus bar to the generator fuse to the regulator to the generator wire terminal itself. A friend of mine here replaced his entire charging system before he found a wire broken in mid-run... inside unbroken insulation .

An electrical system diagram is on page 14 of the PDF file of the 1956 owners manual on the members only page. The charging system should be close enough to that in your airplane, since you still have a generator, as opposed to an alternator.

Miles

I had a similar problem, it was traced to a bad connector where the field wire connects to the master switch

I took both the VR and the Generator to different shop. They just called me and stated that the wire leading to one of the brushes in the generator was grounding on the inside of the casing. They think that this will solve my problems. This sounds like the problem because when I would first start the aircraft and switch on lights, the amp meter would compensate for a minute or two then show discharge. I will put it all back together and respond to the forum after it is tested. I hope this works cause my next option will be to pull out my hair.

Larry

Well, heres the scoop. I put the generator back on the plane and everything works fine. What lessons did I learn?

Start with the generator and make sure that you are getting a charge and go from there. I spent so much time on this that I learned alot and got a good look at the aircraft. I see things that I will have my AP do this coming annual.

I ordered a new VR because I thought that was the problem and it wasn't. I spend $200 for the VR but updates in my aircraft are not a total loss. I thank all of you for the advice. That was worth the membership dues in itself.

Larry

Had appx the same problem on a buddie's 172. Grounded the field term-no indication on amp meter. This tells me that it's a bad gen. Owner takes gen to shop-checks good- Troubleshooting more tells me the same thing- bad Generator. Owner says put in a new VR anyway. So he spends $150 bucks on a new zeftronics---Still no good. All wiring checks good-Jumper field wire on gen to field screw on VR(cuts out the master switch)-Still no good. 6 hours troubleshooting and frustrated as hell. I take the gen back off and go back to the generator shop. I watch the tech run the gen and guess what---we've got an intermittent gen-seems the brushes were riding on the outer ends of the commutator and skipping ever so slightly. New brushes and $22.00 bucks later. Generator works as advertised. So the moral of this whole story is to double check everything. Owner wasted $150 bucks on a new VR and I gave him $50 bucks for the old one. I can always use one for troubleshooting purposes.