How tight or loose should alternator belt be?

chata

I bought a 1991 Honda Accord with 121000 miles on it. The car is in pristine condition --- previous owner also had every receipt for every repair made to car including oil changes and general check ups. Anyway 1 month after purchase car would not start, battery dead. I had battery checked and it needed to be replaced, battery was original. Replaced battery and all okay for about 1 month, then the new battery was dead. Is this possibly an alternator thing or maybe even the alternator belt? I read in the manual I should check the alternator belt for wear, tear and tension. All belts on the car are brand new, but I did check anyway and it is new, however what should the tension be. Thank you

swschrad

if it drops more than an inch, it's too loose. this is a very simplistic answer, however.

belts nowadays are automatically tensioned by (curiously enough) a tensioner... looks like another idler on a separate little plate. no repairable parts, it works or it's replaced. devil is spring-loaded and has enough force to seriously damage a finger (like to force amputations,) so you don't monkey around with bare hands pulling belts over pulleys on modern cars.

I would heartily recommend having the alternator/battery combination load tested by a mechanic... that should prove whether the alternator is working or not. they will also have a force-tension measurement gauge to see if the tensioner is holding the belt in spec.

my bet, but for short money only, is on the alternator being daffy. if it tests OK, you have a current leak that is killing the battery, probably in something like an underhood or trunk light, an accessory that doesn't turn off, or a door pin that is allowing the dome light on after you walk away.

oh... not to be insulting, but I should mention this. have you read the manual cover to cover and tried to touch every control? reason I mention this is we have the car dying right after a new owner takes it, and don't ask me how I know this, but you could be accidentally leaving something electric on and not be aware of it.

tblazer503

Not bad... I would have the alternator checked out... I would guess you have either a bad connection to your alternator, your voltage/current regulator is going bad, or your alternator is going bad... usually it is the first.. those connections will sometimes corrode depending on the area... then the second, which usually requires purchasing another one... I believe you should be okay w/ a rebuilt one, unless you want to spend bookoo bucks on a brand new one. Either way, check both.

chata

First of all I thank both of you for your advice. I was not insulted by your statement had I read the owner's manual. That is the first thing I did. There was alot of useful information, unfortunately none of it was applicable to my problem. I know just enough about cars to be dangerous, at least that is what my son tells me. My first thoughts were there was a drain on the battery because it happened so suddenly the first time, there wasn't anything. After replacing the battery and it again going dead after a month I was then convinced there was something draining the battery. I always turn off the stereo, air conditioner, heater, cruise control, etc., before getting out of my car. I did check for the door lights, interior lights but not the trunk light which I will do this evening. The only thing I have not checked and I will also do is turn off the alarm. Last week it held a charge for 2 days. This week it has held a charge for 5 days. I will also check the belt tension and see how loose it may be. Thanks again for all the information from bother of you.

bburton1

Well I fried one alternator when the belt slipped-apparently they heat up when they are not going fast enough-belt was slipping.

Also I had an alternator to fail just after the engine was worked on by the dealer-the mechanic told me a new guy got the belt too tight and the alternator squalled and they had to replace it -was under warranty. I have had a couple of friends to have alternator failures just after someone replaces the belt.

So i guess there is a happy median-too loose and you burn the diodes out-too tight and you cream the bearings.

swschrad

there ARE tension specifications for new and used belts, and they can be measured with the correct tool... looks like a plank with a couple of feet you press on the belt, and read the tension off a gauge... and your finer shops should have 'em to double check what the tensioners are doing.

not exactly a top tool on Joe Sixpack's gift list unless he has a fleet of his own he works on. also doesn't fit nicely in a zippered pouch under the seat.

7937

I once had an 89 Honda Prelude with 140k miles on it. The original alternator croaked while driving in heavy traffic one day. I tried the cheap repair way and fitted no less than 3 rebuilt alternators which all failed. One of them overcharged the battery so much that the acid boiled out of it. That alternator also blew my headlights. At idle it was putting out 16 volts. Way too high. High voltage can also damage expensive components such as the computer. On top of that it's very difficult to change alternators on that model car. It sits between the engine and firewall with little room to work in.

So please do yourself a favor if you have to replace the alternator. Fit an original manufacturers one even though it costs more. I don't think your model car will have a belt tensioner.

cutehumor

so alternator bearings only go bad when someone puts a belt on too tight? my g/f car alternator bearings went bad when a tech from a texaco repair shop put on a new serpentine belt on. maybe about 6 months later the bearings went bad. hard to prove, eh? I did notice that the belt looked like it was halfway on the idler pulley when I replaced her alternator.

the remanufactured alternator from autozone (limited lifetime warranty) I replaced it on 9/3/02; it's been 4 months with no failures. am I out of the clear?

7937

A few of those rebuilt alternators I had lasted up to 3 months. The problems seemed to be in the solid state regulators which were not up to the job. I think the remanufacteres use the cheapest components they can find.

swschrad

and can also cause early failures in a/c compressors and p/s pumps as well. your typical modern car has a tensioner that automatically provides the correct tension via a spring-loaded idler.

assuming the idler turns and the spring doesn't get gutless. but the belt companies also distribute tensioners, so it should not be a "factory part" and if replacing a belt still does not result in proper tension, the mechanic can order one up quickly.

I have seen several different grades of alternator rebuilt kits... between them, you can see the difference in the quality of the parts. a rebuild should also include truing the contacts on the rotor shaft so the new brushes fit correctly. insulation resistance should be checked on both sets of coils to prevent early failure and catch any nicks from disassembly.

you skip steps and use crap instead of parts, it's gonna fail. you take apart 50 alternators and end up with 10 after swapping not-obviously-failed parts around, it's gonna fail. there's a reason the $29.95 90-day replacement warranty alternators are not $109.95 3-year warranty assemblies.