1990 CASE 580K. Recently acquired used. No gauges work. Got the instrument console out. Cleaned it up. On the tach, there's 3 wires to the tach/hour meter. One's power - got power when on. One's ground, confirmed continuity. On goes to the alternator. Confirmed continuity there, and attached to the tab on the back of the alternator that's in the right location - near the regulator. However, not getting any RPM measurement and hour meter's not turning. Since it's a special sine pulse that's supposed to come from the alternator to the tach, and I have a digital VOM, not sure how to test to see if I have the correct alternator. Suggestions? Also, I would have thought that the hour meter would have turned if it had power, but guess that it's trigger must also come from the alternator. Any experience there? Thanks,
Are you charging?
Excellent question. Just got the machine and hadn't checked everything. The alternator was supposedly "new". I get 12.4v (after battery charging externally) at the battery and at the battery lead at the alternator when not running, and get 12.2V at the alternator to battery lead when running. So I would guess that the short answer appears to be no. Should I presume then that it's the voltage regulator? None of the gauges work, so hope that there's no dependency there. What should I test next? thanks,
bad ALT bulb or dirty bulb contacts. I have a newer 1998 580SL but I'll bet its the same problem as mine. If the ALT light circuit is bad (fuse or relay or bulb or bulb contacts) then the alternator will not have the current it needs in the field coil to start charging. Once the alternator starts to charge it will generate its own current and wont need the ALT idiot light current. The tachometer runs off the "w" terminal on the back of your alternator. If the alternator doesn't work thent he tack wont work...and probably the hour meter I'm guessing. If the rest of your guages dont work then start at the fuse box. Do you have an electirical schematic?
I have a schematic. But the gauge box is out entirely. Trying to get it into shape. There's only one fuse for the instrument console, and it's good. I get power there. However, the circuit board in back is a mess. I'm working on working around it. I'll look into the alt light circuit, perhaps do a work around just to see if that's the problem. I'll let you know. thx
kb9nvh, thanks for the advice. You were quite correct! I was part of the problem by taking out the gauge box to work on it. Also the schematic for that circuit was on two pages and I figured out which fuse (turn signal and horn) it was on. Then discovered that while the bulb was good, one of the tabs on the circuit board was broken where it connected to the plug. All that fixed and GREAT news, the alternator is charging and the hour meter is working. However, no tach. I now get a solid DC voltage from terminal W on the alternator, so I can only assume that the alternator isn't the right one for providing the pulse needed for this tach(?). Any additional thoughts? Thanks for your help in fixing the key issue (charging),
Checked voltage at W terminal again. Get an even 7.2V with the digital VOM in DC mode and 16.1V in AC mode. Don't know if that tells anything though. I'm getting a good 14.3V charging at the alternator so happy about that.
I do not know what type of signal to expect from the W terminal? I would assume it would be just AC and proportional to the alternator RPM but that's just a guess. I'll see what I can find on that.it might be a voltage level as well. I'm betting you just have some bad grounds and broken circuits if your fuse box looks anything like mine, I'm surprised anything works at all. LOL
Well, thanks to you guys and other posts about wiring and gauges, I now have all of them working - with the exception of the tach. Which I am now convinced that the signal from the alternator just isn't the pulse that's needed for the tach. Hour meter runs fine. Thanks for all the advice and help in this post and others that I've asked about electric. Lights are a real mess, but that's a lot less important than some other things that need addressing first. Thanks again.
Have you ever figured the tachometer out? I've been trying to get mine to work with no luck. Even changed out the alternator. Just pegs right to 3k when the turn the machine on and it doesn't move from there with engine speed. Driving me crazy, I would like to figure this thing out.
I know this an old thread,just came across it my tach and hour meter is working,but over time it seems to have gained about 500 rpm I know the engine running the same as it always has really not a big problem any ideas?Charging is fine just bothering me a little.Would be hard to find a better 580k series 3 2 wheel drive standard hoe 1600 hrs everything works sorry for to long story lol.