[Guest]

My alternator drive belt snapped Thursday night, and I wondering about how to determine how much tension the new one should have? I didn't see any posts on this, and its tension obviously isn't super-critical like the timing & balance belts, but I was wondering if anybody had any tips as to how tight to set it. Is there an affordable gauge for this, and if so, what should the reading on it be? I was thinking about just estimating its tightness as best I can, then driving it to my mechanic to do a final tightening. Is there a huge risk to doing this? Thanks.

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[Guest]

I would imagine there is some expensive tool somewhere that measures it but I was do it by eye. Or by ear... It should have a little slack you can bend the belt up or down with your fingers maybe 5mm or so.If the belt is squealing you know it is loose. You want it tight but not so tight that it is hard to bend up or down. Make sense? I think your only risk short term would be a snapped belt you would know it right away. If it is too loose the belt may just fly off and you would be either stuck, and/or the belt would be ruined. To tight I think you could possibly do damage to the bearings in the alternator.

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[Greimann]

Porsche, being Porsche, specifies to to use the P9201 tool to set tension on the accessory belts as well as the balance belt, but I have never heard of any one actually thinking that is necessary. Just tighten it reasonably tight, so there is about 1/4" deflection along the longest span with thumb pressure. If it is too loose, it may squeel some when cold.

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[Cloud9...68]

Thanks for the replies to my alternator belt tightness question; I was thinking along the same lines, but with Porsche being Porsche, I was wondering if there was a critical (and expensive) procedure involved.



But it turns out the belt tension is the least of my problems. The belt was relatively new, as is the alternator and AC compressor, so I was puzzled as to why it snapped. The alternator pulley turns freely, and I didn't originally suspect the AC compressor pulley, because I have had cars' AC compressors seize before, and it makes a violent, shrieking noise, which the 968 didn't.



However, when I checked the AC compressor, the grooved wheel that's driven by the belt is very loose against the main pulley; it's basically just wobbling against the pulley, not fitting snuggly on it at all. It rotates easily, but seems to be broken loose. The main pulley is also turning relatively freely; it's not seized up, but this situation definitely isn't right. Something must have seized, causing the belt to snap (without making any noise(?)). The AC was not on when the warning light came on.



Is this potentially something that's fixable without disconnecting the compressor from it's freon lines, or do I need to take the car to a shop that's equipped to deal with freon (I know a great mechanic who's worked on the car a lot before)? I only drove it maybe two minutes after the belt snapped; any idea how far the car can safely be driven (in the daytime, of course) with no alternator? It would be nice to avoid the hassle of another tow, but I wouldn't risk it if there's even a small likelihood that it would die before I made it to the shop, which is about a half hour from my house. Thanks.



Andy N

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[Greimann]

If the AC pulley buggered, the fix is going to be replacing the compressor with a new / rebuilt unit. Not usually too many compressor fixes can be done in the car.



Don't even think of driving 1/2 hour without an alternator. 1/2 a block would be OK, not 30 miles.

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[flash]

i wonder how long this car would run on the battery - we use to do that in a race car - no alternator at all - just ran on the battery - would go for about 50 minutes - was points ignition and carburettor though

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[Greimann]

The electrical demands of a computerized fuel injecttion motor make having full voltage during operation paramount. The sensors that feed the ECU with informarion are primarily resistance devices that depend on a predictable voltage to commnuncate accurate engine parameters.



As voltage declines, the information to the computer becomes corrupt and the engine performance will drop off dramatically. At some point, the fuel and timing maps will fail to keep the engine running at all.



The computer, sensing it's own demise, will become self-aware, and in a last desperate act of preservation , fire the air bags in self-defense.



Ok. I made the last part up, but I'm sure the rest is true! <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />

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[Cloud9...68]

I'm sure Dave's right; I was just wondering. My first car was a 1969 Datsun 2000 Roadster, and it's alternator once died. From the time I started noticing symptoms (radio stopped working, windhsield wipers running very slow, etc.), I was able to drive it maybe 5 minutes in a desperate attempt to get home before it quit. The 968's accessories at this point still work normally, and it fired up without hesitation when the tow truck dropped it off in front of my house, allowing me to pull it into the garage. But I won't risk it.



For another daydream, it sure would be nice if there was an alternator drive belt available for a non-AC equipped version of the car. Then I could install it, drive the car to a shop where they could remove the compressor and either repair it (unlikely), or at least I'd have a driveable car while waiting for a rebuilt one to arrive. Especially since my other car is also dead at the moment with a very challenging problem. And there'd be no rush to even fix the AC, because I won't be needing it for a few months anyway. There's no chance a belt like this exists and is readily available, is there...?



Andy N

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[Bart]

When I lost the alternator belt last summer I drove about 15 miles home with no problems. Parked the car for about a week (I was leaving town for a trip when the belt let go) and it started right up to move into the garage for the belt replacement.



FWIW

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[rustech]

I once drove a car home 60 miles on two batteries with the lights on at night. During the day, I'm confident I could have gotten further without the lights on. Different car however.

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[flash]

yeah dave - that's what i was getting at - just wondering how long before the higher demands come into play



cloud - there is a belt out there for cars with no ac - since lindsey makes a delete bracket, they can probably tell you what belt to use

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