How tight should alternator belt be?

I thought the alternator was dying on my 84 1.7 non A/C Jetta since it's got down to around -20 degrees. It was fine in testing so I replaced all the corroded wiring up to the battery but I still get symptoms of a failing alternator after driving for 15-20 minutes. Now it's dawned on me that the belt squeals a bit and get's unbelievably hot. It must be the cold that has caused a change in the chemistry of the belt or something.

Anyway, does the squealing and the burning hot belt mean de facto that the belt is slipping, or could it be too tight? Is there a better test? It seems "pretty tight", but I could definitely get it tighter if I needed to. Any conventional wisdom on belt tightness? Could it be something else? Thanks. Ben

1984 Jetta 1.7 1986 XJS 5.3
Reply to
j brontey
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With a good belt using moderate thumb pressure, press down on the longest section in the middle between pulleys. You should be able to press, deflect the belt, one inch. However this is a "rule of thumb" and it may need to be tighter. VW belts tend to be short and narrow and therefore wear fast. Also water and debris is splashed on it from the right front wheel causing more problems. Start with a new belt.

Joe

Reply to
Joe R

Alternator belt: 2-5 mm deflection between the pulleys (pretty tight to me :). Fix it quick since once the alternator belt goes, you have to remove the other 1 or 2 belts to install a new one. First check to see that the A/C (if you have it) and power-steering pump belts deflect 10 mm. Also pick up a Haynes or Bentley :)

Darryl.

Reply to
Darryl

Fortunately I have neither A/C nor power-steering. Based on your descriptions, I have changed the status of my belt tightness assesment to "pretty loose". It just still seemed pretty hard to believe that it could slip--it just doesn't seem like it should be so hard to turn that it would slip. Thanks for your help, I appreciate it. Ben

1984 Jetta 1.7 1986 XJS 5.3
Reply to
j brontey

There's more to belts slippping than just tension. The section of the belt has to match the pulley. If the pulley has worn, or the surface is contaminated the belt will slip. If the surfaces have become glazed..., etc.

There is a magic spray called 'belt dressing' that can be remarkably helpful in some cases. It should be a couple of dollars a tin. They (usually) contain silicone so DON"T spray while the engine is running or let any get near the air intake as the silicone aerosol will pass through you engine and spoil the O2 sensor. I don't imagine it would do the MAF any good either.

You might want to take the belt off, treat it and reinstall to be on the safe side.

Charles

P.S. Remember that aerosols hang around in the air for a while.

Reply to
Charles DH Williams

Thanks for all your help, Bought a new belt for $10 at Canadian tire and put it on snuggly. It's clear that the old belt was worn and on too loosely as everything seems fine now. Ben

Reply to
j brontey

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