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Case 580SK Gauge Problems

julesy

New Member
Joined
Sep 1, 2019
Messages
3
Location
95023
Hi All,

I have a 1993 Case 580SK 4X4 and none of the instrument panel gauges working correctly. I replaced the battery about 4 months ago and it starts like a champ even though it is sitting unused a lot. The gauges have not worked as long as I have owned it, and I'm finally summoning up the gumption to get into this. I've been reading other posts here on the issue and this has been extremely helpful. Following the advice here, I've performed the following -

Found and ensured that the instument panel breaker is fine.
Taken apart the panel and investigated the connections. So far this looks pretty good.
Found that the if I rev the engine to full, the Tach reads about 500rpm.

Based on seeing that the tach does work somewhat, my next suspicion is the alternator. As suggested, I checked the output from the W cable on the back of the alternator in AC mode. I am using a an autoranging digital multimeter, so I hope this does not affect how this unusual signal is read.

Pulling the yellow red wire and reading the output from W in AC mode, grounding to a bare point on chassis, I get 0.2 V. If I rev the engine, it gets up to almost 1V. Checking the wires coming into the back of the instument panel (yellow red to black orange), I get exactly the same reading as I did at the back of the alternator. Based on this, I'm assuming it is not a grounding issue.

My current conclusion is that I have a faulty alternator and should replace this before going any further. Does this seem correct? What else should I be checking? Am I possibly reading this incorrectly?

There is no alternator warning on the panel, but given nothing is working, I'm not assuming that means anything.

I'll deal with the other gauges later. I think this is going to be a long road.

Thanks in advance,
Julesy.
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,865
Location
WI
what's the running voltage at the battery??? if that's above 13, then your alternator is fine. The W is wild three phase, if the three phase wasn't working, then the voltage would be low. I don't know why the W voltage is so low, but that's not the first thing I'd check without a manual telling me to check it.

Do you have voltage to the instrument panel? Do you have voltage going to any of the senders? Do you have any wiring diagram?
 

julesy

New Member
Joined
Sep 1, 2019
Messages
3
Location
95023
Hi,

The running voltage across battery is 12.35. Measuring from the back of the alternator to chassis gives the same, 12.35. I was checking the W as it was the direct feed to the tach and I thought it was good to check. I had been under the assumption that the alternator was fine as I've had no problems starting, although when I got the machine originally the battery was toast so I replaced.

There is voltage to the instrument panel. Some lights work - park break warning. When I turn the key, the battery indicator goes to the lower of the green area as it says it should in the manual. The manual states it should go higher once the engine is running. This is beginning to sound like the the alternator is bad, as if as you say the alternator should be putting out 13-14 then maybe that is why the battery gauge never rises again, as it is only receiving 12v, key turned or engine running.

I have the giant mechanics manual and I've been working through it, but all of this is new to me, so I'm learning as I go.

Is this now a confirmed bad alternator? What should I check next?

Regards,
Julesy
 

thepumpguysc

Senior Member
Joined
Mar 18, 2010
Messages
7,445
Location
Sunny South Carolina
Occupation
Master Inj.Pump rebuilder
I've always relied on the voltage test AT THE BATTERY as to the condition of the alt..
Sitting voltage 12.0-11.8..
running voltage should be MORE.. around 13.v
IDK if the big box parts store can test a "tractor" alternator..?? but if they could, I dam sure would pull it & have it tested..
U could get a 25.00 "load tester" & put a load on the battery & then see if the alt. kicks on & charges it..
BUT if u DO have to replace it, get a direct exact replacement.. Theres an azz-load of threads about replacing an alt. w a different one & now this or that doesn't work..{tach mostley}
 

edgephoto

Senior Member
Joined
Aug 13, 2019
Messages
727
Location
Stafford, CT
The W terminal is unrectified voltage. You need to have your meter on AC not DC volts for this.

If there are no on board computers you could do the old school "is the alternator working" test. While the engine is running disconnect the battery. If it stalls alternator is not working.
 

fpgm04

Well-Known Member
Joined
Dec 31, 2009
Messages
214
Location
USA
Julesy,

As you stated the alternator light is not working, consider that the alternator excites through the lightbulb circuit on your machine, if the lightbulb is bad or corroded contacts, then the alternator will not excite and produce power. So if you don’t have the ALT light illuminating before starting the engine, that needs to be resolved or manually excite the alternator to get it generating power.

I would definitely take a few minutes and check the ALT light bulb circuit before digging into the alternator.

As thepumpguysc stated, if you do replace the alternator, get an exact replacement as the tachometer functionality/accuracy is tied to alternator design.
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,865
Location
WI
12.35v means the alternator is not working, you need to verify the alternator is getting power, then you can confirm it's bad. If it's not getting power to the excite terminals (through the ignition circuit) then it won't charge even if in perfect condition.

Getting it checked at a parts store should tell you the same info.
 

julesy

New Member
Joined
Sep 1, 2019
Messages
3
Location
95023
Hi,

Firstly, I wanted to thank you all for your help and apologize for not getting back sooner.

I've started digging into the alternator circuit more to see what is happening. I've included the wiring diagram and a shot of the instrument connector.

When I turn the key to the on position, I get 11.7 Volts from T2 (Power for warning lamps and guages) to T15 (ground) and the same from T9 (Oil temperature guage) to T15. The results are the same if I use the Tachometer ground instead as I wondered if there might be a problem there.
Looking at the wiring diagram, it shows that the white-orange, 23F should connect to T2, T4 and T9. At both T2 and T9, I see a white-orange wire and read hot with the key in the on position. T4 and T5 are the Alternator warning circuit. I've checked continuity across t4 and T5 on the circuit board. The bulb is fine.

According to the wiring diagram, T4 should be another white-orange which is hot with the key in the on position, as per T2 and T9. In this case, T4 shows 0V and is in fact a thick black-red wire. T5 is a green white wire. They both head off into the wiring harness. I'm stumped at this point. I'm almost tempted to rig t2 to T4 temporarily to see what happens, but I don't want to damage anything.




IMG_4822.JPG IMG_4825.JPG
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,865
Location
WI
according to that diagram you have one "control/excite" wire going to the alternator, and that same terminal is connected to the tachometer. is there a separate W terminal on the alternator? Do you have switched battery voltage supplied to one of the alternator terminals? (voltage with the key on, no voltage with the key off)
 

edgephoto

Senior Member
Joined
Aug 13, 2019
Messages
727
Location
Stafford, CT
The D- connection at the alternator is the excite wire. The yellow/blue wire should have voltage on it with the key on. Disconnect it at the alternator while everything else is connected and check for voltage with the key on. You should have battery voltage.

Also make sure your alternator is getting a good ground.

If you have a good case ground on the alternator, battery voltage at the D- terminal at the alternator you have an alternator problem.
 
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