help with 555d charging circuit

[backhoeblake]

Hello, new to group. working on a 1995 555d. trying to troubleshoot charging circuit. Other thread mentions putting a 200ohm resistor to by pass a missing battery temperature sensor. I have the sensor but don't know how to verify it's working properly. The resistance across it is 168 ohm. Voltage going in on the blue/red stripe is 12.25. The voltage coming out on the blue/white stripe is 10.33. are these the correct values? Is there a place to get a replacement sensor, if this one is failing? Also 12.25 volts into sensor is always on, even when the key is off. Is this correct? thanks

 

[Harry in Ky]

That sounds pretty close as far as I can see. The sensor and related circuit are PROBABLY not your problem. What makes you think it might be? Does the battery light on the dash work? That's part of this as well. Is this a Lucas or Marelli alternator? Both were used, and the temp sensor wiring will work with either one as I recall.

 

[backhoeblake]

The backhoe belongs to friend of mine. when something like the lights coming on at night for no reason, he just cut the wires to the lights and took them off the machine. none of the gauges and indicator lights work so it's hard to diagnose anything. I'm basically grasping a straws. The alternator is relatively new. I don't know the brand. There are no markings on it. I've attached pictures. The original problem is that the battery goes dead. I don't know if the alternator is not charging it or if there is a ground leaking the power through a bad wire. He pulls the battery cables off when he's not using it. I have the machine for a while. I'm going to keep the battery connected for a few days while not using it to see if the battery drains. What's an easy test to see if the alternator is charging? I will see if i can find out the make of the alternator.

 

[Roadworthy]

Measure the battery voltage when the tractor is not running - it should be about 12.6. Measure again with the tractor running. It should go up to about 14 if the alternator is working. That's the easiest test I can think of.

 

[backhoeblake]

Battery voltage is 12.28 without the engine running. I have to put the sensor back into the circuit. I took it out because there were too many splices in the line. I don't trust that setup. As an added note. With the battery out I checked the resistance between the pos. and neg. battery cables. I'm getting 5ohms. Isn't that supposed to be an open circuit?

 

[backhoeblake]

Checked Battery terminals with machine running at about half throttle. No change in voltage(12.28). Put battery tester on battery. Voltage agrees 12 minus volts. When test with rocker switch, shows weak. 850 cca battery. That shouldn't effect the charging circuit.

 

[MountainBuck]

With 12.25 volts on the sensor when the key is off will be a parasitic drain to the battery which is why your friend pulled the battery cable off when not in use. However there may be more than one parasitic drain.

I'd pull off the positive terminal and put an amp meter in series between the post and the battery cable to see how big this drain actually is when the key is off. Careful with this to make sure you have a meter big enough to handle this task. If the drain is too big, it will blow the fuse in the meter.

When your friend cut the wires and took off the lights, is this when the instruments went dead? I would look into trying to restore these gauges, at least the oil pressure gauge.

 

[Harry in Ky]

I have a similar load tester. Take the ground cable off the battery. Clamp the black lead of the tester onto the negative battery post. connect the red lead to the ground cable terminal. The meter should read zero. If you see any voltage reading it indicates a draw that will eventually run the battery down. The greater the voltage, the greater the draw. That's a starting point. If you see a draw, start disconnecting things that are battery live until the draw is gone. Start with the alternator positive battery post and the temp sensor terminal. Biggest suspects to start with. If that's not it, start pulling fuses one by one and see what that gets you.

Maybe you don't have a draw, but if it's not charging the battery will eventually go dead anyway. The battery charge light light has to work because it's part of the charging system. With that alternator it's what starts the charging process. It looks like a Marelli "style" alternator, but most of the ones I see are clearly marked so this may be an aftermarket replacement.

 

[backhoeblake]

Answer to Mountainbuck: I don't have an amp meter, but will get one. Any idea how many amps I likely to see so I get one that is strong enough?

Answer to Harry: With the load tester set up as you suggested, I get the full 12volt reading. I will start pulling wires as suggested.

There was a short in the wiring around the throttle cable a while back and my friend cut the burned wires out. There's a good chance he cut a necessary one. I'm looking into replacing some of the instruments int he instrument cluster that no longer function. Without them I'm flying blind. and as you say, the indicator light may be part of the problem.

 

[Harry in Ky]

You're half way there. And you didn't need an ammeter.