Something is going on with my old Case 850E dozer and I am at my wit's end as to what it can be. It had been sitting about two weeks and when I went to start it... nothing. Nothing electrical works. The dash lights will not even come on when I turn on the switch. First thing I check is batteries and cable connections. All good. Two 12v 1000cca batteries. Both fully charged showing 12.8v each and both load test good. Load tester can get so hot I can't hold it and still showing good. All fuses good and showing 24v across both sides without load. As soon as I put any kind of load on the electrical system, no matter how small, the voltage at switch and everywhere else except at the battery and positive cable post on starter drops to near zero, even when grounding tester directly to battery. It does not matter what I try to power up. 24v to ignition switch, turn it on and voltage drops to near nothing. 24v to light switch, turn on light switch and drops to near nothing. 24v to horn switch, press button and drops to near nothing. Etc. I have tried going through and disconnecting things one at a time with the same result. Starter and solenoid are good. I can jump the post at the starter and turn the engine over. Plenty of voltage and amps at starter. The little plastic guard is still there, so I had to expose the screw and use a jumper wire. I messed up and touched the side of the starter the first time. 12 gauge solid copper wire was instantly welded in place and burnt in two before I could yank it off. That confirmed that I have plenty of voltage and current from batteries and good ground connection. I have been messing with this thing for several days and making no progress. I installed a new ignition switch this morning. Nothing changed. Anybody have any ideas? Thanks.
Hook your load tester positive to the center between the two batteries so you get only one, the negative tester cable to a good clean frame ground, NOT the battery terminal and see what you get. I'm saying you might have a ground issue, possibly the disconnect switch or a bad cable? I think there's a power relay in the mix behind the panel that might be involved but I'm not all that familiar with your machine so we'd need a schematic to know for sure.
Thanks for the reply, lantraxo. I tried bypassing the disconnect switch by just putting both cables on the same post already. However I have not tried checking between the batteries to just get 12v. I will try that in the morning when I get home from work and let you know what I get. My gut tells me it's probably a ground problem, but I have checked and cleaned every ground I can find so far with no luck. I have a parts catalog for the machine, but no repair manual and no wiring schematic. There are three relays behind the panel. Two brake relays (part number S243589) and one 75 amp relay switch (part number 1546542C1). I don't know how they are supposed to work, so I can't test or bypass them, but the problem is the same even when they are disconnected. There is also a 75 ohm resistor (part number F22316). According to my tester, I get between 75 and 80 ohms across it, so it should be good.
Yeah, what I'm thinking is that by conecting one end of your load tester to the first battery and then the other end to a frame ground, you will test the ground circuit for the batteries ability to carry the high current. Testing the ground cables and connections, not the battery. Another way to look at it is to ask where you're connecting you meter when you read 24V at the key switch? If you connect the meter to a metal frame ground and the power goes away when you put a load on it, what happens if you ground your meter to the negative battery terminal instead of a frame ground? Okay, if you only have one big relay it may be that it's a starter relay. Still, should be one big fat wire that stays hot on one of the two larger terminals, that may be your issue? If it's not a ground issue, you have to have bad connection or broken wire between the big starter terminal and the instrument panel, or a bad fuse or circuit breaker in the line somewhere.
The problem is the same even with the tester grounded to the battery terminal. There is a hot wire going to the relay. Same symptom there. Any load anywhere on the system and the voltage drops to near nothing. It's raining now and I have to work again tonight, so I think I will wait until tomorrow morning to try your suggestion about testing across just one battery. I will try to find a wiring schematic online also.
When you're making the measurement which 'drops to near nothing', do you have the meter between a positive terminal somewhere and the chassis of the machine? If that is the case, then you won't be able to tell if it's a ground problem (i.e. the chassis is being pulled-up to the +ve rail) or if it's a positive-side problem (i.e. +ve rail falling down to the chassis.) If you can extend the black lead on the meter to reach the ground terminal on the lower battery directly, then measure to the fuse board again (or wherever 'drops to zero'). If the voltage there still collapses when you put on a load, the problem is in the positive side, not in a ground. Similarly, if you put the black lead to the +ve terminal on the high battery, then measure to your fuse board, you'll have 0V with no load, but if you have a big voltage with a load on, you'll know the problem is in the +ve side. Basically, the voltage that disappears when you put on the load is still somewhere in the machine, it's just hiding itself - and that somewhere will be across the fault. If you keep measuring the different sections of the circuit, you'll find where it's hiding, and you can narrow it down. Sorry it's generic, I don't know the specific machine.
I got a break between showers and wasn't in bed yet, so I ran down to the farm for a few minutes. Checked voltage between batteries grounded to frame as suggested. 12.6v I then decided to run a jumper wire from the positive battery cable to the hot terminal on the ignition switch. Turned switch on and dash lights come on. Hit hit starter and she fired right up and everything works. So the problem is apparently somewhere in the hot feed to the switch. I pulled the ignition fuse and checked it again just to make sure. For some reason I put my tester on the positive feed wire at the switch and I have 6v with the fuse removed? Should it not be zero with the fuse pulled? This is confusing.
Just a thought, with the rain/moisture you are dealing with, could you have some corrosion in the fuse block? If any corrosion, that could explain your 6 volts. I would check the back side of the fuse block as well as the actual fuse terminals in the block that you are putting your fuse into. Also I seem to recall the E series only having 3 or 4 fuses with the fuse block being fed off of a wire at the starter solenoid. If so, disconnect the positive battery wire (for safety). Then take the nut loose on the starter solenoid that has the main battery feed wire on it as well as the main fuse block wire. Inspect, clean, and reinstall. It is possible that your fuse block has a poor feed connection that is causing your main issue.