Alternator Belt Adjustment

[artbuc]

After replacing timing, PS and alternator belts last winter, I left the alternator belt a little loose to be sure I didn't ruin the alternator bearing. Wife tried to use A/C yesterday and told me no cold air. The alternator belt doesn't squeal when I turn on the A/C or rev the engine.

Is it possible that the alternator belt is loose enough that it is slipping on the A/C compressor? Could it be slipping without squealing?

How much deflection should I have on the alternator belt? I read somewhere that you should have 3/8 - 1/2" of deflection per foot of belt length between pulleys (measured from where belt loses contact with the pulley). The belt length between the crank and alternator is about 11". That means I should have less than 1/2" of deflection and I have 5/8".

I am always afraid of overtigthening fan belts. Thanks for your help!

[lenore]

yep tighten it a little, then try to twist is 90 degrees if it goes further than 90 it is probably too loose.

[code58]

After replacing timing, PS and alternator belts last winter, I left the alternator belt a little loose to be sure I didn't ruin the alternator bearing. Wife tried to use A/C yesterday and told me no cold air. The alternator belt doesn't squeal when I turn on the A/C or rev the engine.

Is it possible that the alternator belt is loose enough that it is slipping on the A/C compressor? Could it be slipping without squealing?

How much deflection should I have on the alternator belt? I read somewhere that you should have 3/8 - 1/2" of deflection per foot of belt length between pulleys (measured from where belt loses contact with the pulley). The belt length between the crank and alternator is about 11". That means I should have less than 1/2" of deflection and I have 5/8".

I am always afraid of overtigthening fan belts. Thanks for your help!

artbuc- If the alt. belt (also a'c) is loose enough that you aren't getting any a/c, you are bound to have squealing. I don't think there is much chance of having NO a'c and tightening the belt that small an amount and regaining your a'c. I agree with Lenore in the amount that the belt should be tightened but I would 1st. visually check to see that the compressor clutch is engaging when the a'c is on. You may have a fuse blown or a small hole in the condenser from dabrie that let the R134 out. Tap the low side valve with a small screwdriver to see if the system still has a charge. Could the system be a little low and the low pressure switch shut the compressor clutch down? I would personally be a little surprised if you have NO a'c and it is just a minor belt adjustment. Let is know what you find out. <_<

[artbuc]

After replacing timing, PS and alternator belts last winter, I left the alternator belt a little loose to be sure I didn't ruin the alternator bearing. Wife tried to use A/C yesterday and told me no cold air. The alternator belt doesn't squeal when I turn on the A/C or rev the engine.

Is it possible that the alternator belt is loose enough that it is slipping on the A/C compressor? Could it be slipping without squealing?

How much deflection should I have on the alternator belt? I read somewhere that you should have 3/8 - 1/2" of deflection per foot of belt length between pulleys (measured from where belt loses contact with the pulley). The belt length between the crank and alternator is about 11". That means I should have less than 1/2" of deflection and I have 5/8".

I am always afraid of overtigthening fan belts. Thanks for your help!

artbuc- If the alt. belt (also a'c) is loose enough that you aren't getting any a/c, you are bound to have squealing. I don't think there is much chance of having NO a'c and tightening the belt that small an amount and regaining your a'c. I agree with Lenore in the amount that the belt should be tightened but I would 1st. visually check to see that the compressor clutch is engaging when the a'c is on. You may have a fuse blown or a small hole in the condenser from dabrie that let the R134 out. Tap the low side valve with a small screwdriver to see if the system still has a charge. Could the system be a little low and the low pressure switch shut the compressor clutch down? I would personally be a little surprised if you have NO a'c and it is just a minor belt adjustment. Let is know what you find out. <_<

Thank-you lenore and code58. I increased tension a little - reduced deflection from 5/8" to 3/8". Before I could easily twist the belt more than 90 degrees, now I can twist it to almost 90 degrees but have to use alot of force to do it. Yesterday was hotter than the day my wife "tried" to use A/C for the first time this year. After adjusting the belt, wife said A/C worked great. (I wish I would have driven it myself before making the belt adjustment because my wife isn't always reliable when it comes to describing her RX).

Code58, I am with you re the squealing which is why I asked the question. Here is my best guess: the new belt was slipping but not squealing because it had not yet glazed. I'll let you know if anything changes. When you consider the low contact angle of the belt on the A/C compressor pulley, I would think you need pretty good belt tension to drive it.

I have wanted a belt tension gage for over 30 years now and I think I am going to buy one. I'm getting too old to be guessing if I have enough belt tension!!

[Randy&Bonnie]

..

[code58]

Code58, I am with you re the squealing which is why I asked the question. Here is my best guess: the new belt was slipping but not squealing because it had not yet glazed. I'll let you know if anything changes. When you consider the low contact angle of the belt on the A/C compressor pulley, I would think you need pretty good belt tension to drive it.

I have wanted a belt tension gage for over 30 years now and I think I am going to buy one. I'm getting too old to be guessing if I have enough belt tension!!

I'm not a mechanic by trade, but worked on cars for about 40 years. I think it's pretty hard to over-tighten a new belt. They usually stretch a small amount after a few miles. You'd have to use a pry bar or something and really reef on it, but I suppose it's possible. I too have always been careful when tightening my belts. It's kinda like doing valve lash adjustments, it's a acquired "feel".

You learn something new every day eh, artbuc? I don't see what year RX you have artbuc but I have had some recent experience with belts. I recently replaced the a/c-alt. belt on my DIL's 99RX300. I used a Dayco Premium belt (the original belt was a Dayco/Toyota) This is the belt with the notches in the grooved side. After a couple of days my DIL informed me that it was squawling for about 1/2-1 second at startup and then would quite. I knew I had adjusted it tight enough (I've been adjusting belts for over 50 yrs.), and figured at 120k that the compressor was finally going. I told her not to use the a/c until I could fix it. Before I got a chance to get the car she told me it had done it a couple of times with no a/c on. I checked the belt and it was tight enough and so I spent the next 1 1/2 days tearing everything apart to check the water pump, both idler pully's, alt. bearing, comp. bearing, comp., etc. (checked it all 1st. with mech. stethescope), and found nothing. I was at my wits end (it had never made the noise for me but I had heard the noise once when my son started the car). It squealed like a banshee. The thought finally came to me to compare the new belt to the old one. I took a mic and miced all the dimensions on both belts and there wasn't a lot of difference but there appeared to be a small difference in the angle of the taper of the walls of the grooves on the new belt. I put the old belt back on, adjusted it to the same tension an viola- no more squawling. I feel the squawling was until it spun the alt. up some, as the a/c pulley would offer no resistance without the a/c on. I probably could tighten it tight enough to stop the squawl but I feel then it would be overtightened to compensate for the improper angle of cut on the grooves. I will return it and get a Mitsuboshi orig. eq. belt. I thought because the orig. belt was Dayco that it would work well but as sometimes is the case, after market even by an orig. eq. man. is not built to orig. eq. standards. Darn belt wasn't cheap either! :( Roger

[code58]

Code58, I am with you re the squealing which is why I asked the question. Here is my best guess: the new belt was slipping but not squealing because it had not yet glazed. I'll let you know if anything changes. When you consider the low contact angle of the belt on the A/C compressor pulley, I would think you need pretty good belt tension to drive it.

I have wanted a belt tension gage for over 30 years now and I think I am going to buy one. I'm getting too old to be guessing if I have enough belt tension!!

I'm not a mechanic by trade, but worked on cars for about 40 years. I think it's pretty hard to over-tighten a new belt. They usually stretch a small amount after a few miles. You'd have to use a pry bar or something and really reef on it, but I suppose it's possible. I too have always been careful when tightening my belts. It's kinda like doing valve lash adjustments, it's a acquired "feel".

You learn something new every day eh, artbuc? I don't see what year RX you have artbuc but I have had some recent experience with belts. I recently replaced the a/c-alt. belt on my DIL's 99RX300. I used a Dayco Premium belt (the original belt was a Dayco/Toyota) This is the belt with the notches in the grooved side. After a couple of days my DIL informed me that it was squawling for about 1/2-1 second at startup and then would quite. I knew I had adjusted it tight enough (I've been adjusting belts for over 50 yrs.), and figured at 120k that the compressor was finally going. I told her not to use the a/c until I could fix it. Before I got a chance to get the car she told me it had done it a couple of times with no a/c on. I checked the belt and it was tight enough and so I spent the next 1 1/2 days tearing everything apart to check the water pump, both idler pully's, alt. bearing, comp. bearing, comp., etc. (checked it all 1st. with mech. stethescope), and found nothing. I was at my wits end (it had never made the noise for me but I had heard the noise once when my son started the car). It squealed like a banshee. The thought finally came to me to compare the new belt to the old one. I took a mic and miced all the dimensions on both belts and there wasn't a lot of difference but there appeared to be a small difference in the angle of the taper of the walls of the grooves on the new belt. I put the old belt back on, adjusted it to the same tension an viola- no more squawling. I feel the squawling was until it spun the alt. up some, as the a/c pulley would offer no resistance without the a/c on. I probably could tighten it tight enough to stop the squawl but I feel then it would be overtightened to compensate for the improper angle of cut on the grooves. I will return it and get a Mitsuboshi orig. eq. belt. I thought because the orig. belt was Dayco that it would work well but as sometimes is the case, after market even by an orig. eq. man. is not built to orig. eq. standards. Darn belt wasn't cheap either! :( Roger

artbuc- you mentioned the "low contact angle" on the comp. belt- my DIL's RX has about a 90 degree turn around the comp. pulley, maybe I didn't understand what you meant but that doesn't seem like "low contact" to me. It get's a pretty healthy bite on that pulley.

[lenore]

I believe he is talking about the taper of the v in the belt. I stuck with OEM from Lexus of Plano Texas. They were cheap.

Here is the site:

http://www.trademotion.com/partlocator/ind...m?siteid=213808

[code58]

I believe he is talking about the taper of the v in the belt. I stuck with OEM from Lexus of Plano Texas. They were cheap.

Here is the site:

http://www.trademotion.com/partlocator/ind...m?siteid=213808

Now I've gotcha- appreciate that clarification Lenore. I don't like using after market parts unless I have to, but I was in Pep-Boys for some other parts and thought I'd take a chance on the belt (Dayco) because the original was Dayco/Toyota. That's not the first time I've been bitten by after market belts- you'd think I'd learn! :( Y/T- Roger :)

[code58]

I believe he is talking about the taper of the v in the belt. I stuck with OEM from Lexus of Plano Texas. They were cheap.

Here is the site:

http://www.trademotion.com/partlocator/ind...m?siteid=213808

Now I've gotcha- appreciate that clarification Lenore. I don't like using after market parts unless I have to, but I was in Pep-Boys for some other parts and thought I'd take a chance on the belt (Dayco) because the original was Dayco/Toyota. That's not the first time I've been bitten by after market belts- you'd think I'd learn! To top it off, the belt was $22. You'd think I'd learn! :( Y/T- Roger