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  1. #1
    Sam Carlson
    Tutorial Bot euromobile900's Avatar
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    Saab(s)
    '90 900 LPT with a flat-nose conversion
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    Lights (voltage?) flicker at idle.

    I've been having this problem pretty much constantly since I first noticed it in August, but it seems to be getting worse (or else it does it worse in the wet climate we've had of late). Basically, at idle I notice all the lights (headlights, tail, brake, dome) flicker and dim in time with the vibrations of the engine. All the while, my volt gauge is reading a happy tick above 14 volts, but I'm thinking its needle can't respond fast enough to display anything with the flicker.

    In addition, on some wet days, the belts will set up a pretty bad squealing after a minute of running (noise starts suddenly and goes away quickly after maybe 30 seconds), which I don't think is the crank pulley because I replaced that with a new one just three years ago. The reason I mention the squeal is because it seems to be related to everything else. When the flicker is at its worst is often also when I get squeal. The squeal usually is accompanied by some change in voltage, and often happens right after some lights are turned on or the brake pedal is pushed.

    Is it just wishful thinking that my crank pulley isn't shot? The new (3 year old) one is MTC brand (maybe should've gone with OEM?), and the oil seal behind it is dry. Could it be an issue with my alternator grounding wire? I have some red poly bushings in the alternator mounts as well, and while they are beginning to crumble, the alternator doesn't shake around very badly yet.

    Any advice or experience anybody can add would be much appreciated. I have a feeling this problem is going to develop from a nuisance to a real trouble sometime soon.

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  2. #2
    Saab Fan
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    Saab(s)
    '93 900s
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    Easy way to eliminate your crank pulley is just draw a line across the edges of the 3 pulleys. The AC pulley is hard mounted to the center, the others are connected by the rubber. If the hard mounted pulley moves in relation to the rubber mounted ones, you know the pulley is separating. I just steal some bright nail polish from the wife to paint small marks on the edges.

    This post caught my attention because of the belt squeal. I have the same issue. Crank pulley is fine. I just had it off to replace the sensor 3 months ago and it looked fine. I get a squeal when the car is first started. If I blip the throttle a few times it goes away. Belts are all new, tension is good. The alternator bushings are less than a month old. I'm thinking it's a bearing in the alternator getting ready to go. I've found that switching lights/fans on while the squeal is around will make it more noticeable. My thinking is the additional load on the alternator combined with the poor bearing is more than the belt traction can handle.

    After the initial episode, I have no problems at all until it sits for a while and I start it again. No voltage issues either, just annoying squeal. I don't want to shell out the $$ for an alternator if it's not the problem, so going to just drive and watch for a little while.

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  3. #3
    Sam Carlson
    Tutorial Bot euromobile900's Avatar
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    Saab(s)
    '90 900 LPT with a flat-nose conversion
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    Quote Originally Posted by Raub View Post
    Easy way to eliminate your crank pulley is just draw a line across the edges of the 3 pulleys. The AC pulley is hard mounted to the center, the others are connected by the rubber. If the hard mounted pulley moves in relation to the rubber mounted ones, you know the pulley is separating. I just steal some bright nail polish from the wife to paint small marks on the edges.
    I know about this trick, and it will be employed next time I start the car. I always just used chalk myself, but nail polish sounds like a much more waterproof solution

    Also, welcome to SaabWorld! Glad to have another c900 enthusiast to contribute to the knowledge pool

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  4. #4
    Saab Fan
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    '93 900s
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    Thanks for the welcome. You guys have put a lot of work into this site so far!

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  5. #5
    Steve
    spoolin' thin air mt.aero's Avatar
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    '02 9-5 Aero, '89 900S
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    Have you had your battery checked? My first guess is that its on its way out.

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  6. #6
    Sam Carlson
    Tutorial Bot euromobile900's Avatar
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    '90 900 LPT with a flat-nose conversion
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    Quote Originally Posted by mt.aero View Post
    Have you had your battery checked? My first guess is that its on its way out.
    Why would that make a flicker? It is healthy, so far as I know. It should be--it was replaced in January of 2009, so I will be extremely disappointed if I don't get at least another 2 years out of it.

    I also have a (roughly) 2-year-old voltage regulator and crank pulley. I've been so busy with evil yard work that I haven't had much time to do much other than paint a line on the crank pulley. I'll maybe go for a drive tonight to eliminate the crank pulley from the mix, and then in the next few days I'll go through the alternator wiring to check stuff out.

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  7. #7
    Steve
    spoolin' thin air mt.aero's Avatar
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    '02 9-5 Aero, '89 900S
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    Quote Originally Posted by euromobile900 View Post
    Why would that make a flicker?
    It will cause a flicker because its not holding enough voltage to power everything in the car at once. So, when you hit the brakes and the brake lights come on, it needs the extra voltage (which normally comes from the battery) and you just dont have it. Its now putting more load on the alternator at idle and the alternator doesnt produce enough voltage at idle to power everthing fully so you are getting the flicker. The extra load is likely what is causing the squeal too. I just had this on my wifes 900. The battery that went bad was only 11 months old. Brought it in and got it tested and sure enough, it just couldnt hold juice well anymore. I got it pro-rated since it had a warranty and paid $10 for a new battery.

    Where is your in-car voltmeter hooked up. Pre or post battery?

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  8. #8
    Sam Carlson
    Tutorial Bot euromobile900's Avatar
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    Saab(s)
    '90 900 LPT with a flat-nose conversion
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    It takes its positive feed from the instrument cluster wire harness, so I'd think that would be post-battery, eh? It is one of the newer VDO ones that doesn't respond quickly to fluctuations. I think it has some kind of dampener circuitry in there or something, because the needle doesn't snap up or down the way the old ones did.

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  9. #9
    Steve
    spoolin' thin air mt.aero's Avatar
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    gotcha. It does read post-battery then. It must not see the small fluctuations. Are you getting the flicker when the engine is reved up at all? I would just get your battery checked for good measure, especially since most places do it for free. Thats the best price! If thats not it, I would then suspect your battery cables next.

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  10. #10
    Saab Fan
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    Saab(s)
    '93 900s
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    Update on my squealing issue: removed all the belts and cleaned all the pulleys really well with a wire brush and some emery cloth. Squeal gone. The belts sit in the pulleys at least an 1/8" deeper since I cleaned them. I guess 20 years of belt wear was built up on them.

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