When doing electrical troubleshooting you never ASSUME anything. Doing so will only hurt your cause. Battery reading of 12.1 VDC doesn’t indicate a bad or weak battery, that’s an ASSUMPTION. When you take readings across “TERMINALS” tells us nothing. We have no clue which terminals. You need to tell us which step you are on and the results of each test. At that point we will have a better idea of what you are seeing. Remember we can de hundreds of miles away from you and help no clue what you are doing or seeing. You must help us before we can help you.
Corroded ring terminal, battery cable
- Thread starter rigoletto
- Start date
I have sanded down any possible oxidation on the terminals. Also, new copper hot wire on battery. With a new solenoid, where could there be the V drop?
But, Rivets, on my post #49, I said the 2 terminals on the solenoid. Am I missing something? There are only 2 main terminals (that connect to the heavy main wires) on that, the other is the spade post, to the very thin wire.
Starter solenoids have either 3 or 4 terminals. I don’t guess when trying to help. If you expect me to know what you are talking about, then I’m getting out of this thread. Hard enough to help someone electrical troubleshooting from hundreds of miles away, when they understand this type of troubleshooting. Even harder when they think they know more than those trying to help, as you are assuming again and didn’t understand my last post. Good luck in solving your problem, as I’m ASSUMING you know more than me, so I’m going for a stiff drink.
- Joined
- Feb 19, 2020
- Threads
- 91
- Messages
- 11,467
Not really clear as to what position the ignition is in here.
Okay the small terminal should be reading around 12v with the ignition switch held in the start position. Across the two large terminals with the ignition held in start position should read near zero voltage drop. Now across the starter (main terminal to starter case) should read very near the battery voltage when things are right.
Now if you are reading 3.5-4.0 across the large terminals of solenoid with the ignition switch held in the start position it tells me that the internal contacts are heavy burned and that the solenoid needs replacing. But the 2.0v on the small terminal is worrying as it should be either zero or near 12V depending on the ignition switch position provided all the safety switches are working. Without full voltage on the small terminal the solenoid can not fully pull in the main contacts. A bad safety switch or wiring terminal can cause the voltage problem at the small terminal and that problem area would have a huge voltage drop across it.
Also really could stand with the model number from serial number so I could try to a wiring schematic of the mower. Most likely with it having a three post solenoid the safeties are the brake.clutch and the PTO switches. Just note the ignition switch is also part the safety system.
- Joined
- Feb 19, 2020
- Threads
- 91
- Messages
- 11,467
Rivets, Yes you can. This is basic electricity and electronics. And starter is still providing a path to ground too.
This is what is called a voltage drop test. If voltage present then there is high resistance is present. Higher the resistance the higher the voltage. By doing voltage drop tests you will find where bad connections are present. You are doing same thing basically when you test between the battery negative post and the frame ground or when you test from one end a wire to the other end of the same wire. Multiple resistance in series have difference voltage drops depending the resistances present.
Say the starter is 1 ohm and the all connections to it presents as .01 ohm nearly all the voltage will dropped across the starter. But if say the solenoid contacts are presenting .5 ohms in the same circuit then it would register a third of the voltage and starter would only see 2/3 of the voltage. This is how you traced down bad connections. Now a starter normally pulling 80amps at 12v will have a resistance of .15 ohms so any resistance across contacts will greatly affect the delivered voltage and current. Many of the DDVMs out there can not read in the milli-ohms range so without voltage drop tests you will not find bad connections; unless, you just lucky enough to replace the bad component(s).
Resistance in series divides the voltages not the current. Resistance in parallel divide the current but not the voltage. This why two 1/2 watt resistors of the same valve in parallel is the same as an one watt resistor but half the resistance. It is a little more complicated then this depending on the values involved but this is the basics.
Guess I’ve taught it wrong for 50 years. I’ve always taught that to measure voltage drop through a component you measure one side of the component to ground and then the other side of the component to ground. The difference between the two readings is the voltage drop through that component. Lucky I’m no longer teaching. This will probably be my last post on this thread.
It's raining today, so cant do any testing on the mower. But maybe Monday when the rain is over. I am a basic learner, struggling, with the help of any member offering here, much appreciated. But when it turns to uncalled for anger and resentment with accusations and criticism on top of that is very unfortunate, and not expected. 1st time I have experienced this on any DIY forum. I have always looked up to all the members here, still do.
SN is 1C048C20044, , model 13A4667F118 MTD. Thanks, Star, for detailed follow up. It is starting to be clearer now. Will repeat tests and answer some of the questions you posted. Then go from there. It has cleared up now, trying to go out there again to do more tests............
PS: solenoid is new.
Last edited: