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Old 10th February 2005
jimmythefly's Avatar
jimmythefly jimmythefly is offline
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Join Date: Jan 2002                                                
Location: Washington State | 86 900T16
My Saabs: 1986 900T
Posts: 158
Default Quick help needed! charge light/ alternator jump?

Trying to get this fixed in the next two hours or so, your help is appreciated!
1986 900 turbo 16 valve.
Quick questions:

1. Can I hook a wire from fuse #7 directly to the D+ alternator terminal, bypassing the dash charge warning light? (thereby supplying battery voltage to the D+ terminal without having to worry about if I have a burned out dash bulb or faulty wiring)

2. Is it necessary to supply this voltage to the D+ side, once the car is running, or is it just for start-up purposes?

Signs and Symptoms:

A few days ago, driving home, charge warning lamp on dash kept coming on for several minutes, then going out, then coming on. Hasn't come on for a full day. Yesterday, with engine running (dash light not on), voltage between battery terminals was 14+ volts.

This morning car started as normal. Then power windows very slow, wipers slow. within 5 minutes car had stopped running. Batter voltage on non-running car is about 11 volts. Dead.

Got a jump from a friend. With my car running now, but not hooked to hers, voltage across battery was about 11.8 volts, but kept reducing to 11.7, then 11.65, then 11.6, etc.

Dash bulb is good, but does not come on when I turn the ignition on. My diagnosis is that there is a loose connection or whatever somewhere going to or from the dash bulb. A loose connection or almost broken wire explains the bulb going on and off over the last days.

The question is, if the connection has now entirely failed, does this explain why my alternator is not charging the battery. Hence my first question about bypassing the dash bulb.

Thanks for your help, trying to get somewhere by tonight, would love it if I could fix myself.

PS. I'm at work now, car is on side of the road. I have the Bently manual with me. Difference between D+ and B+ on back of alternator with car running was OK, but I forgot to check D+ and ground when ignition is on. Plan to do that when I go back to get it, but would love to also have some suggestions from this board as to what else I could do. Thanks!

Last edited by jimmythefly; 10th February 2005 at 01:14 PM. Reason: title, spelling
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Old 10th February 2005
saab90089's Avatar
saab90089 saab90089 is offline
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Join Date: Sep 2002                                                
Location: Pennsylvania--USA
My Saabs: 3-89 C900T--1black=mine, 1green=dad, 1 metalic gray convert. w/airflow=dads
Posts: 1,234

Well it sounds like its an alturnator problem to me. I did not think the charge-light effected the amount of charge that the alt puts out. Because other wise a dead charge light would mean the alturnator wouldn't do anything.

I know i've had an alturnator die on me with out the charge light even coming on.

I normally test the alt by: taking a volt reading before start, and during start....shouldn't drop below like 10 for long. Once idleing it should read like 13.x no more then 14 and no less then 12.8. Then turn on the low-beams, then highs and it shouldn't go below 12......sometimes i'll also crank the heater fan on 3.

From what you have told I would have to point at the alturnator first......pershaps it is just the brushes more specifically.

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Old 10th February 2005
MSOEMiller's Avatar
MSOEMiller MSOEMiller is offline
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Join Date: Feb 2002                                                
Location: Alhambra, CA
My Saabs: '87 900 8v N/A & '88 900 SPG, Both 5 spd
Posts: 1,222

Also, reach under the alternator and make sure the ground wire is properly connected to the engine block (At the alternator bracket). A loose ground here will cause your car to die.
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Old 10th February 2005
saab_speed_maniac_2k6's Avatar
saab_speed_maniac_2k6 saab_speed_maniac_2k6 is offline
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Join Date: Dec 2003                                                
Location: Texas
My Saabs: 1990 900sT, 87 900s, 87 900s, 97 900 seT
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WAIT!!!!!!!!!!! dont buy anything yet. the problem is ur voltage regulator. it is located in the back of your alternator. it is just 2 screws. take it out and check it out to make sure that it has enough of the lead or whatever to make contact. i almost garentee it will not have enought. feel the shaft inside the alternator and makesure it is smooth. and if it is then jsut go buy a new regulator with has costed me in the range of 12-46 dollars us. i have had a lot of alt problems lol. try this first because to remove the alternator is a b***h. i mean a BIG one. try this then let me know how it goes.. o yeah if u can take off ur oil filter and check the ground. my just corroded through and fried my alternator. lol that i y i say removing the alt is a B***H. this is my 4 time removing it. lol
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Old 11th February 2005
jimmythefly's Avatar
jimmythefly jimmythefly is offline
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Join Date: Jan 2002                                                
Location: Washington State | 86 900T16
My Saabs: 1986 900T
Posts: 158

Thanks, y'all. turns out is was the alternator. Saab shop I had it towed to confirmed that the possibly incorrect replacement alternator I had installed some months ago by a non-saab place was the problem.

Also, I got advice elsewhere that my original idea of jumping past the dash light would possibly fry the alternator so I didn't do it, there are other ways to check the circuit, just take a bit longer.
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