Rusty42 7 #1 Posted April 11, 2016 Hello to all! Great forum you have here! I recently picked up a 1975 B80 4spd with a charging problem. While troubleshooting the charging system I found a wire backed out of the terminal crimp at the rectifier. During the repair I noticed that the ammeter was disconnected and the 2 wires butt connected together. I hadn't notice the ammeter not working when I bought the tractor but there was no way it was gonna work like that! I tested the ammeter and found an open circuit between the positive and negative terminals. If connected, this would have resulted in a "no crank" condition. I then tested for continuity between the threaded posts the terminals are fastened to and found less than 1 ohm resistance, AH HA! I removed the ammeter and cleaned the oxidized/corroded terminal, nut, and threaded post. I reassembled using locking washers to ensure contact, tested the connection and now had less than 5 ohms resistance in the ammeter circuit. I installed the ammeter and it works like a charm!! 5 Share this post Link to post Share on other sites
Terry M-(Moderator) 2,126 #2 Posted April 11, 2016 (edited) Sounds like someone just " gave up" trying to troubleshoot the problem. Glad you figured it out. Oh, and welcome to Red Square.... Edited April 11, 2016 by Terry M Share this post Link to post Share on other sites
squonk 38,980 #4 Posted April 11, 2016 I don't understand how you can clean the connections and end up with more resistance. Unless the corrosion was so bad it shorted the terminals together kind of like a dirty battery top? 2 Share this post Link to post Share on other sites
Rusty42 7 #6 Posted April 11, 2016 2 hours ago, squonk said: I don't understand how you can clean the connections and end up with more resistance. Unless the corrosion was so bad it shorted the terminals together kind of like a dirty battery top? Less than 5 ohms is the spec for the ammeter circuit. Cleaning the connections repaired terminals of the ammeter. Initial testing showed infinite resistance in the ammeter circuit. 1 Share this post Link to post Share on other sites
953 nut 51,876 #7 Posted April 11, 2016 Clean and tight is the solution to most electrical problems. Lots of us have replaced Amp Meters with Voltage meters as they will give you a better indication of what is happening. 2 Share this post Link to post Share on other sites
Rusty42 7 #8 Posted April 11, 2016 4 minutes ago, 953 nut said: Clean and tight is the solution to most electrical problems. Lots of us have replaced Amp Meters with Voltage meters as they will give you a better indication of what is happening. No doubt if the ammeter was actually bad it was gonna getting replaced with a volt meter. An ammeter is a good indicator of work, but current is often misunderstood. Thanks for the warm welcome from everyone! 1 Share this post Link to post Share on other sites
squonk 38,980 #9 Posted April 11, 2016 9 hours ago, Rusty42 said: Less than 5 ohms is the spec for the ammeter circuit. Cleaning the connections repaired terminals of the ammeter. Initial testing showed infinite resistance in the ammeter circuit. Ok you said it was less than 1 ohm that's what confused me which isn't a hard thing to do! 1 Share this post Link to post Share on other sites
Retired Sparky 526 #10 Posted April 11, 2016 Hello and TO Share this post Link to post Share on other sites
