Cougar Posted June 12, 2005 Share Posted June 12, 2005 The light is on because there is trouble with the circuit. It is not getting the proper 12 volts from the supply circuit, fuse 13. When you jumper the 10 amp fuse to a hot fuse does the light turn off as it should? Link to comment Share on other sites More sharing options...
AKIRA Posted June 12, 2005 Author Share Posted June 12, 2005 "When you jumper the 10 amp fuse to a hot fuse does the light turn off as it should?" yes the charge light (and the other "wrong" ones) turn off. ----------------------------------------------------------------------------- could it be the diode in series with the light? now this might be because I didn't test it directly on each end of the diode, but at the wires to it in the fuse box. my multimeter has a diode tester, the manual says it should have a .4v - .7v, and the oppisite way should have "OL" (shorted devices will indicate near 0v. shorted devices will indicate near 0v and an open device will indicate "OL" in both polarities.) - direct quote from manual. my diode shows .597v one way, and .352v the other way, when it should have a reading only one way any tips on taking the instrument cluster out? Link to comment Share on other sites More sharing options...
AKIRA Posted June 13, 2005 Author Share Posted June 13, 2005 I took the cluster out: the brown wire is good the circut board strip is good to the diode the diode is good the strip to the light is good the light is good thats as far as I got, its getting late here. but I tested the other diodes, one of them is bad, it gives about 32 milliamps eachway, but it is not the one in series with the alt wire path. do you think this is the problem? I will be tracing more tomorrow Link to comment Share on other sites More sharing options...
Cougar Posted June 13, 2005 Share Posted June 13, 2005 I doubt the diode is bad. Even if it is leaking as the readings indicate it may be; though I think this due to other components in the circuit causing this to happen which will have to be isolated to get a good reading; the problem is still no voltage is getting to the 10 amp fuse and the readings show the diode is conducting so it is not the problem. If voltage were getting to the diode it would pass on to the fuse. There is still a bad connection between the two fuses somewhere. You need to follow the wire back and keep looking for the point where the voltage is being dropped. Don't worry about the other diodes that are on different paths as they won't help with this problem. They are for isolating other warning lights. To check them you really need to isolate one end so the meter doesn't back feed through something else in the circuit. We are trying to find out why voltage is being blocked getting to the fuse. Link to comment Share on other sites More sharing options...
AKIRA Posted June 13, 2005 Author Share Posted June 13, 2005 ok I traced the circut through the instrument cluster board: the bw wire from the fuse to the the plug is good the line to diode is good the diode is good??? (more later) the line to charge light is good the light is good the line from the light to the other plug is good the brown wire from plug to the fuse is good from the test I did with my multimeter, it said the diode is good, but it has over 5.1 Mega-ohms of resistance, and measuring from the post the brown wire hooks onto to the post the bw wire hooks onto it reads a resistance that is almost the same (~5.1 Mega-ohms). If i measure it the other way it reads "OL" because of the diode. Link to comment Share on other sites More sharing options...
Cougar Posted June 13, 2005 Share Posted June 13, 2005 If you are measuring the diode in the standard resistance mode then I don't think that is a valid test. You need to be in the diode test mode. If you want to prove the diode is good then place a 12 volt source on the anode side of the diode and see if the alternator works. If it does, then the diode is ok. If the diode was the problem then you should see 12 volts on the anode side. If I remember correctly, the brown wire coming from the alternator ties to the 10 amp fuse, through the fuse the wire turns black and that then ties to the light and the diode. Is that correct? Also, what color wire ties to the anode of the diode? It is that wire that needs to be tracked for a problem of what is blocking the voltage. Link to comment Share on other sites More sharing options...
AKIRA Posted June 13, 2005 Author Share Posted June 13, 2005 yeah, the regular diode test function says its ok. -------------------------------------------------------------------------- "If I remember correctly, the brown wire coming from the alternator ties to the 10 amp fuse, through the fuse the wire turns black and that then ties to the light and the diode. Is that correct? Also, what color wire ties to the anode of the diode? It is that wire that needs to be tracked for a problem of what is blocking the voltage." -------------------------------------------------------------------------- no, the wr wire goes from the alt to the 10A fuse, becomes brown and goes to the instrument cluster circut board. a path on the board the brown plugs into goes to the diode, then to the light, then to the other plugin which is where the bw wire plugs in and goes to the 15A fuse, which the black wire then hooks to there is no wire going to or from the diode, just a path on the circut board, and I checked both, they show a normal resistance - I traced the whole path, it seems good. and there is voltage getting to the wr wire, 2v with it on, 7v with it running and I forgot, is the andoe the positive or neg side? Link to comment Share on other sites More sharing options...
Cougar Posted June 13, 2005 Share Posted June 13, 2005 Ok, thanks for the clarification. Your last statement says that the 15 amp fuse has a black wire tied to it. This wire is the side of the fuse that should should supply power to the fuse, correct? If so, you need to see why power is not getting to that wire. The voltages you are seeing on the WR wire right now are not really significant. We need to have 12 volts powering that line. The arrowhead side of the diode needs to have a positive bias on it for the diode to conduct. Link to comment Share on other sites More sharing options...
AKIRA Posted June 14, 2005 Author Share Posted June 14, 2005 ----------------------------------------------------------------------------- Your last statement says that the 15 amp fuse has a black wire tied to it. This wire is the side of the fuse that should should supply power to the fuse, correct? If so, you need to see why power is not getting to that wire. ----------------------------------------------------------------------------- but power is, it has got the 12 volts all the way up to the end of the bw wire, I just haven't tested the vd past it because of the dificulty of reaching a probe back behind the cluster while it is plugged in, so it has to be from the end of the bw wire to the end of the brown wire I'll try to fit a probe back there and measure the vd of the other stuff in the line I attached a drawing of the part of my circut, with color labels Link to comment Share on other sites More sharing options...
AKIRA Posted June 14, 2005 Author Share Posted June 14, 2005 I think I found it, I read the voltage before the light, 11.6V. after, 3.2V. yet the resistance from the bw wire prong to the light side of the diode is only 10.4 ohms, with about 6 being from the light fillament. I switched the light and its backing plug with the fuel one, it made no difference, so its not the bulb or its plug. the place where it plugs in doesn't look any different from the others any ideas? Link to comment Share on other sites More sharing options...
Cougar Posted June 14, 2005 Share Posted June 14, 2005 I think I found it, I read the voltage before the light, 11.6V. after, 3.2V. yet the resistance from the bw wire prong to the light side of the diode is only 10.4 ohms, with about 6 being from the light fillament. I switched the light and its backing plug with the fuel one, it made no difference, so its not the bulb or its plug. the place where it plugs in doesn't look any different from the others any ideas? Are the voltages you gave with the engine running or just with the ignition on? I assume that the light is on while you read the voltages. If you didn't make the measurements with the engine running let me know if the light is on while the engine is running and tell me what the voltage is on the connection between the light and the diode. If the light is on with the engine running check to see if the light goes out if you pull off the 'L' lead off the alternator. If it does go out then you may need to replace the alternator. Link to comment Share on other sites More sharing options...
AKIRA Posted June 15, 2005 Author Share Posted June 15, 2005 Engine running: 13.6 volts before the light 6.6 volts after the light engine on: 11.66 before 2.9 after the light is on while the engine is running. the light does go out when I remove the plug, but it can't be the alt. I replaced it with a new one after this problem occoured. we are going in circles here. Link to comment Share on other sites More sharing options...
Cougar Posted June 15, 2005 Share Posted June 15, 2005 Engine running:13.6 volts before the light 6.6 volts after the light engine on: 11.66 before 2.9 after the light is on while the engine is running. the light does go out when I remove the plug, but it can't be the alt. I replaced it with a new one after this problem occoured. we are going in circles here. The fact that you now have 13.6 volts input makes me think the alternator is working for some reason but the warning light is on. Before, the voltage was about 11.2 volts with the engine running, correct? If the alternator is working but the warning light is still on then there is a few things things that could be wrong. First, lets measure the alternator output to verify what it is putting out the proper voltage with the engine running around 2,000 rpm. We want to have around 14.5 volts there normally. Verify that the warning light is still on. If the warning light is still on then either, the diode has an excessive forward bias voltage, there is a connection problem after the diode, or the alternator is bad. To find out where the problem is, measure the voltage across just the diode. If the voltage is more than .7 volts then that is a problem. If that is ok, then measure the voltage between the 10 amp fuse and the 'L' lead of the alternator. There should be very little voltage drop, no more than .2 volts. If that is ok then measure the voltage at the 'L' lead of the alterntor to ground. It should be 12 volts but it isn't. Do all these tests with the engine running around 1,500 to 2,000 rpm. According to your tests there is a 6.6 volt drop on the line after the light. This is too much. Let me know what the voltages are. Link to comment Share on other sites More sharing options...
Cougar Posted June 15, 2005 Share Posted June 15, 2005 Akira, I went back through the posts again to try and see what happened. It does seem originally that the alternator was not charging and the light was on. The voltage output was less than 12 volts. In post 50 you stated that there was about 7 volts at the 10 amp fuse with the engine running. Is this still true? If so, we need to check to see what is causing the voltage drop there. Check the voltage at the 'L' lead while the engine is still running. If the volage is still around 7 volts there then it appears the alternator is at fault. I know you have tried others with the same results but it has to be the trouble. In the beginning things were a little different somehow. Something changed on us while testing. If the problem is in the alternator it may have happened when your dad was probing around and the alternator worked briefly. Possibly some of the exciter diodes failed. That would explain some of this but it wouldn't explain why you have the proper voltage now, if that is the case. Link to comment Share on other sites More sharing options...
AKIRA Posted June 15, 2005 Author Share Posted June 15, 2005 your right, it used to be lower when the enigne was running. I'll have to wait on the tests until my dad gets back, I can't work the meter and hold the gas down at the same time -------------------------------------------------------------------------------------------------------------------------------------------- If the problem is in the alternator it may have happened when your dad was probing around and the alternator worked briefly. Possibly some of the exciter diodes failed. That would explain some of this but it wouldn't explain why you have the proper voltage now, if that is the case. -------------------------------------------------------------------------------------------------------------------------------------------- yeah, on that, I was reading the meter and holding the common on the neg bat terminal, I told him to touch the probe on each of the fuses, so I could read the vdrop on it. he put it on the 20A fuse at the end and it suddenly worked for a few seconds, he said he looked up and the lights weren't lit up. like I said before, we were unable to reproduce this. also, very early on, he and I was able to make the "wrong" lights dim by shaking the wiring. but it quit doing that, now no amount of shaking will affect it. the output voltage on it changed later, because i remember it had went back to under 12V after that little fluke I am not sure if that happened on the current alternator though. Link to comment Share on other sites More sharing options...
Cougar Posted June 15, 2005 Share Posted June 15, 2005 You can place a little wedge in between the accelerator cable or just pull on the cable if want. You may be able to just read the voltage without setting up the idle and not have very much of a difference. I just wanted to find out what the voltage is at a normal engine speed. If the voltage at the 'L' lead is still around 7 volts and the output voltage is above 13 volts with the engine running you are done. Replace the alternator. Link to comment Share on other sites More sharing options...
AKIRA Posted June 15, 2005 Author Share Posted June 15, 2005 yes it was 11.2 or so before. ------------------------------- from your last post, here it is lots of stuff but the main things: L lead to ground: 7.03 Volts alt output : 13.83 Volts Crap, I just bought that alt. also, the voltage guage shows in the white (alittle over 12), but the charge light is still on. anyway here are the rest: alt output - 13.83V and the light is on with this reading diode is about .555V each way, but the actual test says "ol" one way and .491 the other (and I can isolate this diode by taking the charge light out) the drop from the fuse to L lead is 53.6 milivolts both the 10A fuse and L lead shows 7.03 V to ground all tests were done at ~2,000 rpm i am going to hoovers junk yard to pick up a guage cluster and an alt. I had two other alts in this thing, are they all bad now? Link to comment Share on other sites More sharing options...
Cougar Posted June 15, 2005 Share Posted June 15, 2005 Good job on the tests. The diode is showing a normal voltage drop so it is fine. The problem now is the voltage on the 'L' lead should be 12 volts but it is drawing too much current internally and that is what is keeping the warning light on. The alternator is bad sorry to say, though the voltage output is about right. Edit: You asked if the other alternators are bad. Whatever the problem was originally that caused the field lead to not work seems to have gone away. You could try swapping the other units in place to see if they will work now. If they are alright then things should work normally. Link to comment Share on other sites More sharing options...
AKIRA Posted June 15, 2005 Author Share Posted June 15, 2005 I put one of the alternators in, and it now works normally EXCEPT: the voltage fluctuates rapidly while it is running, and I can see the lights dim a small amount in tune. it goes from about 14.8 to 15.2 volts. nothing too bad, but I am not sure if it did it before this thanks for all of your help here Link to comment Share on other sites More sharing options...
Cougar Posted June 15, 2005 Share Posted June 15, 2005 Keep an eye on the voltage as 15.2 volts is a little high. I really like to see no more than 14.8 volts. This may mean your regulator could fail on this. If the voltage goes any higher I would swap out that alternator. I assume that the regulator is built in on this. Make sure the battery doesn't over charge by feeling the sides after a good drive. If it is hot, then you have to change the alternator. The small voltage flucuations you see are normal. The alternator can't produce full output at idle speeds. Your welcome for the help. You should be an alternator expert now. Link to comment Share on other sites More sharing options...
edrach Posted June 16, 2005 Share Posted June 16, 2005 Glen, you absolutely deserve a medal for perseverance on this problem! Nice work. Link to comment Share on other sites More sharing options...
Cougar Posted June 16, 2005 Share Posted June 16, 2005 Thanks for the salute Edrach. I enjoy a good challenge, as I think most of us sudo techs here do. It's fun to learn things also. We have a good group of folks here. I see you live in Bothell. Back in the younger years we used to ride our bikes to Ingelwood Golf Club and hunt for golf balls there. Then there was Bob's fried chicken in Kenmore. Link to comment Share on other sites More sharing options...
edrach Posted June 16, 2005 Share Posted June 16, 2005 The golf course is still around, but I think Bob's is gone. This area must have been farm country when you were here. You'd likely not recognize it anymore. Thanks for the salute Edrach. I enjoy a good challenge, as I think most of us sudo techs here do. It's fun to learn things also. We have a good group of folks here. I see you live in Bothell. Back in the younger years we used to ride our bikes to Ingelwood Golf Club and hunt for golf balls there. Then there was Bob's fried chicken in Kenmore. Link to comment Share on other sites More sharing options...
Cougar Posted June 16, 2005 Share Posted June 16, 2005 Too bad we didn't pick up about 20 acres of some of that "farm land" back in the '60's to sell now. Link to comment Share on other sites More sharing options...
edrach Posted June 16, 2005 Share Posted June 16, 2005 That's for sure; especially Woodinville which has turned into Yuppieville. Too bad we didn't pick up about 20 acres of some of that "farm land" back in the '60's to sell now. Link to comment Share on other sites More sharing options...
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