slminneman Posted October 4, 2009 Share Posted October 4, 2009 I have an '89 GL-10 Turbo wagon. It's running fine, but has some electrical issues that I can't figure out. Right now, several of the dashboard idiot lights glow whenever it's running. They're a tad brighter near idle, more faint when at speed, but always on to some degree. The power locks only work occasionally, but that pre-dates this problem. I also had to bypass the ignition switch starter position and install a pushbutton starter, but that was 20K miles ago. Just saying that the car has never had the healthiest electrical system (owned it from new, so it's not from anything that was *done* to it). The voltage gauge shows odd readings...high (15-6V) sometimes, occasionally a little low (usually where there are high electrical loads, so this might not be *that* unusual). When the voltage is high, I can drag it back down by turning on the rear defroster grid. Later in the same trip, I can usually switch that accessory off and all's well again. This particular behavior seems slightly temperature-dependent -- the high-voltage problem seems more frequent on hot days. The battery is recent. The alternator isn't particularly new or old. I've checked for bad grounds in obvious locations around the battery, but they look good and solid. What should test next? What should I be looking for? Any ideas? Like I said, it runs Ok, but it makes me very nervous. I also don't like to play voltage regulator (by switching on/off the rear defroster) when the voltage kicks up for no reason. Thanks! Scott Link to comment Share on other sites More sharing options...
hatchsub Posted October 4, 2009 Share Posted October 4, 2009 From what you've said id say that your voltage regulator is shot in that alternator. It might have just been a bad rebuild. The glowing faintly dash lights is one of the signs that its on its way out. Also the fact that you have high voltage and can bring it down by turning on different accessories. I had a VR go out on me one time and my voltage was spiking 18v:eek:. I cranked the stereo, put on the heat full blast (summer mind u), rear defrost and anything else i could lay my hands on to turn on and was able to get it down to 14 to get to the junkyard and get a used alt. I still have that alt to this day as a spare backup in my trunk. I had way too many alternator problems for me not to. Now i just run an XT6 90amp which seems to have solved all problems for me. Link to comment Share on other sites More sharing options...
Turbone Posted October 4, 2009 Share Posted October 4, 2009 Check the fusible links, located in a small rectangular black box connected to the radiator recovery tank. Its possible that someone replaced them with something thats not correct or that they just might be old and weak. Link to comment Share on other sites More sharing options...
crazyman03 Posted October 4, 2009 Share Posted October 4, 2009 i had that exact same problem on my '88 GL just 2 days ago. Check the actual voltage at your battery (and at the alternator too wouldn't hurt) and see if it is is really spiking. Mine was spiking to 18+ volts before i replaced it. Once done *knock on wood* everything returned to "normal". Link to comment Share on other sites More sharing options...
Cougar Posted October 4, 2009 Share Posted October 4, 2009 The alternators in these cars are a little on the weak side. They do tend to have the problems you describe as far as the high voltage and dim warning lights. While the high voltage is a sign of a bad regulator inside the alternator I believe the dim warning lights are due to bad diodes in it. I recommend you replace the unit with a remanufactured one. Remember to disconnect the negative battery lead before you work on the alternator since the main lead is HOT to the battery. The power lock problem may be due to dirty switch contacts or broken wiring in the door jamb. Link to comment Share on other sites More sharing options...
slminneman Posted October 4, 2009 Author Share Posted October 4, 2009 I checked the fusible links...they looked proper and healthy. I pulled a few fuses while the thing was running, thinking that if I had a minor short somewhere, I might be able to narrow it down this way. The warning lights go out when I pull the 15A fuse labeled "charge" -- does anybody have a wiring diagram that would indicate exactly what the circuit that this fuse connects to actually does? The overvoltage issue is rpm-related...I'll check the voltage in a few places with a VOM with something keeping the revs up. Thanks for the suggestions. The alternator is an easy enough swap, but I thought I'd ask about this latest lead in the mystery. Cheers, Scott Link to comment Share on other sites More sharing options...
crazyman03 Posted October 4, 2009 Share Posted October 4, 2009 yea, that was what i was having. when i was idling it was sitting around 11-12 volts. when i revved it sat around 18+. sometimes when i was warmed up it would go back to normal regardless of rpm. sometimes it would be very spastastic. If you are getting voltage higher than even 12 volts its coming from the alternator. the voltage regulator is built-into it. I can almost guarantee you if you replace it, it will work fine. Link to comment Share on other sites More sharing options...
Cougar Posted October 5, 2009 Share Posted October 5, 2009 I pulled a few fuses while the thing was running, thinking that if I had a minor short somewhere, I might be able to narrow it down this way. The warning lights go out when I pull the 15A fuse labeled "charge" -- does anybody have a wiring diagram that would indicate exactly what the circuit that this fuse connects to actually does? The overvoltage issue is rpm-related...I'll check the voltage in a few places with a VOM with something keeping the revs up. Thanks for the suggestions. The alternator is an easy enough swap, but I thought I'd ask about this latest lead in the mystery. Cheers, Scott If you want to continue checking things out to try and find a problem elsewhere then go ahead, it's your time. The problems you are having are due to a defective alternator. The warning lights are in the alternator exciter circuit. This is so when the key is turned to on, they are tested. The circuit also supplies current to the field windings so when the alternator field builds up it puts out a voltage on that lead and that counters the input voltage and that turns out the lights when the engine turns the alternator fast enough. If there is a problem with the alternator then that voltage drops down and it turns on the warning light. Link to comment Share on other sites More sharing options...
Ricearu Posted October 5, 2009 Share Posted October 5, 2009 To reassure yourself, take your multi-meter, set it to AC current autorange. Put the negative lead on the negative battery terminal. put the positive lead on the alternator b+ terminal (the fat one to the battery) and if you get more than .5v AC voltage you have a bad (backfeeding) diode, which will wonk out the VR and cause high voltage. replace it Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 5, 2009 Share Posted October 5, 2009 The warning lights are in the alternator exciter circuit. This is so when the key is turned to on, they are tested. The circuit also supplies current to the field windings so when the alternator field builds up it puts out a voltage on that lead and that counters the input voltage and that turns out the lights when the engine turns the alternator fast enough. If there is a problem with the alternator then that voltage drops down and it turns on the warning light. That's true for the charge indicator, but when the brake fluid and parking brake lamps start comming on it's because the AC output from the bad rectifier is defeating the diode's in their illumination circuit. But everyone here is correct - no need to test anything - when you see voltage fluctuations per RPM's, flickering warning lights, etc - you DO have a bad alternator. No need for a VOM or DMM or anything else really. Just run right out and buy another alternator. It's the ONLY thing that can cause those symptoms. GD Link to comment Share on other sites More sharing options...
slminneman Posted October 10, 2009 Author Share Posted October 10, 2009 Just as an interesting point, there was almost no AC floating about in any circuit (I saw .1V, tops), and the voltages all seemed pretty normal, yet all of the warning lights were glowing brightly. I know you all were saying there was no question but that the alternator needed to be replaced, and I agreed that the symptoms pointed that direction, but I had to be doing something while I waited for the new alternator to show up. The rebuilt alternator arrived, and I put it in (that is a *very* easy task, compared to my other cars (a small flock of Mazda 323GTX)) -- 15 minutes, start to finish. A tiny bit of lost skin from that radiator fan guard, but not bad. The verdict: all better. No more warning lights or wild voltage swings. Thanks, everybody, for the advice. Link to comment Share on other sites More sharing options...
crazyman03 Posted October 10, 2009 Share Posted October 10, 2009 Link to comment Share on other sites More sharing options...
Ricearu Posted October 10, 2009 Share Posted October 10, 2009 Link to comment Share on other sites More sharing options...
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