1970 580Ck Gas Engine. I replaced the alternator because the battery kept going dead while in use. The old alt. , according to Auto-Zone was defective. Now, when checking for charge, with a digital vom, the voltage is jumping all around. From 9 to 16 volts. Nothing steady. When the engine is off, the battery shows 12.40 volts. (The battery was load tested and shows that it is in good shape.) Now when I do this same procedure on my truck, the same vom shows a steady charging voltage of 13.50 volts. No voltage jumping around. The alternator has a constant 12 volts at the BATT and FIELD 2 connections. Something tells me this new alt isn't charging or I'm missing something. Yes ... This is a used backhoe the I just purchased from a farmer. Proper maint. and repairs were not of quality. Any help would be greatly appreciated. Thank You.
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Electrical Question ...
- Thread starter cajun
- Start date
OldandWorn
Senior Member
Do you have a charge indicator on the machine like a volt or amp meter? Try placing a 12 volt bulb or analog volt meter across the battery just to verify what you are seeing on the digital meter.
Thank You for the relpy. Update: The wire from terminal 1 (field 1) is supposed to come from the ignition switch, (maybe through a lamp/fuse) and become "hot" upon starting the engine. I found this wire laying on the left side of the engine. Along with that wire was a constant "hot" wire. I pulled a volt meter from one of my junk trucks and wired it to the battery. I started the engine and touched the 2 afore mentioned wires together, "Viola" the volt meter jumped to 14 volts. So ... apparently, that is my reason for no charge. Guess now, I get to do some wiring repair.
Ok, have answered my own question on the above reply. There does not have to be a constant 12 volts power on Field1. There just has to be a shot of 12 volts to start the alternator charging. Am I missing a relay or something that will give this shot of 12 volts then shut off? All help is greatfully appreciated. Thanks.
Well I only have 1 wire on the starter solinoid, and yes it does get 12volts when the engine is started, then no 12 volts when the engine starts. I hooked a wire up from this terminal, to feild 1, started the engine up and my starter continues to run at the same time. I don't think this is supposed to be like that. So back to square 1 ...
spanner
Well-Known Member
- Joined
- Sep 2, 2011
- Messages
- 55
- Location
- Sunshine Coast Queensland Australia
- Occupation
- Heavy Equipment Fitter
Cajun, My understanding of a charging circuit goes like this. Power goes from the "ON" terminal of your ignition switch and then through the charge indicator light to small terminal of the alternator. When the alternator is not turning this is effectively a ground so that when you turn the key "ON", the light comes on. This also "exites" the alternator so that when you start the engine the alternator begins to charge. The small terminal on the alternator then becomes "live". Your charge indicator light is now being supplied with power from both sides and with no earth or ground it will go out, telling you that the alternator is charging. I dont pretend to be a " sparky " but this explanation has always worked for me.