Alternator Belt Tension?

I'm sure I've never done this right. So please help!

I'm about to install a new alternator in my 92 Toyota PU 22RE. I've read the service manual, but I don't have the belt tension gauges discussed in the manual.

So, exactly what is the best way to set the proper belt tension for the alternator?

Furthermore, I'm also doing this myself, so I only have two hands which seems inadequate to maintain some tension on the belt while I tighten the bolt to lock the alternator in place.

Any ideas welcome. And thanks in advance!

Chris

Reply to
Chris
Loading thread data ...

99% of mechanics use the ole tyre iron or long screw driver to apply pressure on the alternator and tighten bolts with 10-15mm of play in belt. Easy as pie.
Reply to
Scotty

Just dont over tighten as you will wreck ya new alternator!!!!

Reply to
Scotty

Thanks Scott for coming to my aid!

Ok, I've tried the long screw driver bit too (with a lot of fumbling and slip-offs). I was not very good at it, but I'll try it again.

Here's the BIG newbie question as a follow up:

How do I determine 10-15mm of play in the belt?????

Here's what I've done, but with big question marks flying around my head constantly.

Ok, the belt is on. I use my index finger and press down on the belt between the pulleys. How much force do I use to press down on the belt? It seems I get a huge range of "play" depending on how much pressure I apply. I could never tell whether I am pressing down enough or not.

And when it is "not yet" right, I have to loosen the adjustment bolt and go through the whole hhhhrrrruummmp again to put pressure on the alternator belt and re-tighten and check. You know, last time I changed the belt it took me hours and hours. And when Winter came, the belt started squeeling every now and then when it gets cold... ugggghhhhhhh!!!!

I'm sure it all sounds dumb to you, sorry about that, I'm really just an occasional mechanic (brakes, radiator, power steering, bulbs, small time stuff).

Thanks very much,

Chris

Reply to
Chris

I think that's what I've done before, thus the new alternator. My problem was I really don't know what is loose, and what is tight, not even over-tight. Well, I now know a bit more... at a costly price.

Thanks Scotty.

Chris

Reply to
Chris

10-15mm is yanking on the belt and watching it move up and down half an inch. Up to an inch is fine. Less than that and its too tight and you will wreck the bearings on the alternator.
Reply to
Scotty

Chris,

Isn't there another car around that you can fondle it's belts? Don't overcomplicate it. 1/4" to 1/2" belt deflection at the midpoint between pulleys with enough push thumb push. There will be more deflection if there is a great distance between the pulleys and less deflection if there is a lesser distance between the pulleys. Push as hard as you would push your thumb into the palm of your other hand without hurting yourself.

Paul.

Reply to
Paul.

Hi Paul,

Love the "fondle" part :) And yes, per your advise, I went to another vehicle and fondled its belts. I'm surprised. It also appears to be on the "too tight" side... and oh no! I think I was the guilty mechanic that put those on as well...

My next task will be to reduce the tightness of the second vehicle.

I am getting the idea... at least I now have the concept of "too tight" down. Too loose would help. If I get that, then the "just right" would be between those.

And you're right. I have a tendency to overcomplicate things.

Appreciate your help. Thank you!

Chris

Reply to
Chris

"Up to an inch is fine."

THAT, I think helps me understand better. I thought before that that would be too loose, when in fact, it is approaching the right setting (half an inch up and down).

Thanks again Scotty. With Paul and your help, my confidence is up and I think I know what to look for when I tighten the belt.

Chris

Reply to
Chris

Now, to complicate things just a little. A new belt will stretch just a little so you want a new belt just a little tight. If you are retightening an existing belt, all the initial stretch is gone and you don't want it too tight. Still stay within the 1/4" to 1/2" deflection criteria (I personally thing 1" is a little loose).

If it is your vehicle, a little loose is better than too tight. Too tight ruins bearings. Too loose means the belt slips under high loads and sometimes squeals. Just tighten up the loose belt. Replacing bearings is tougher. If it isn't your vehicle, you don't have the opportunity to monitor the belt to you have to get it right the first time.

Paul.

Reply to
Paul.

Yes, I am re-using the existing belt. Yes it is my vehicle and I will certainly know if the belt squeals :)

Now here are new info regarding the old and the new alternators.

I was at the alternator/starter shop and the tech bench checked both the new and the old alternators. I was very curious as to what exactly was wrong with my old alternator.

Results:

Old Alternator:=======================================

Under load of 40 amps, it generates a little more than 11 volts. The bearings appear to have survived my torture tight belt tension.

On the vehicle, it would occasionally give off teck-teck-teck-teck sound. Reving the engine, the sound would disappear.

New Alternator:=====================================

Under load of 70 amps, it generates a little over 12 volts.

Question:

Did I make a mistake in replacing the alternator?

The problems I was having included, dead battery, the parking brake light AND the discharging/battery dash warning lights are both ON. The engine would not start even when I replace the battery with a fully charged (overnight trickle charge) one. The starter would be cranking with vigor...

But jump-starting using another vehicle works fine.

Thank you Paul and Scotty,

Chris

Reply to
Chris

Agree with the previous comments that a slightly loose belt is far better than a tight one. I've had alternators run several hundred thousand miles and I always keep the belt a bit loose. Haven't lost an alternator bearing yet.

If the battery/charge light is on when the engine is running, then almost surely the alternator output is insufficient. Eleven volts at

40 amp load sounds a bit low but the real test of an alternator is its current output. I've found that a good way to test an alternator is to put a big ammeter (like can be found in auto stores for custom set-ups) in series connected to the battery ground (negative) terminal. I use a hefty -60 to +60 amp meter with a spare battery terminal connected to one of the ammeter terminals and the car battery ground (negative)cable connected via an old copper braided ground wire connected to the ammeter's other terminal. As long as you don't crank it too long and fry the ammeter you can watch the current flow as various loads (headlights, rear window heater etc.) are turned on. If the current goes negative as load is applied, the alternator is bad. If current stays around zero or slightly positive as load is applied, the alternator ouput is keeping up.

The warning light is electrically positioned between the battery and the alternator so that when the alternator can output an amount of current equivalent to the load being asked of the battery no current flow goes through the light and it stays off. If the alternator cannot keep up with the load, battery current will flow through the light and it is thus illuminated. Similiarly, if the light is NOT on with the ignition on and the engine off, the alternator is bad due to an internal open circuit i.e battery current is unable to flow through the alternator to ground. The simultaneous illumination of the parking brake light and the battery/charge light is a peculuarity of Japanese warning lamp circuits. It means nothing and will go off when the alternator circuit is OK.

Hope this helps and isn't too obtuse. Good luck.

Al

Chris wrote:

Reply to
al

(SNIPPED)

Al, if I was you Id invest in a DC Clamp meter. They are SOO much easier to use.

Reply to
Scotty

Thanks Al. I've learned a lot from your response.

I wish the shop had the big ammeter you described. Nonetheless, they had what seemed like an industrial alternator shop test bench, which had an big electric motor, a jig to mount and hold the alternator under test, the cables used to measure voltage and amp, and the analog meters.

Not knowing how this test bench works, all I could see was the amp pegged at 40 amps and 11 volts. The tech said that 40 amps was all it could deliver. New, this alternator is rated at 60 amps.

I now understand the operation of the battery/charge dash light. Wish the service manual explained it as well as you did.

Chris

Reply to
Chris

Actually Al, this describes me, I am ashamed to say. But even before this reminder just now, I found myself staring at the lights before I crank the engine. Guess I learned the hard way as well...

Chris

Reply to
Chris

Good news everyone!

I have re-installed the new/rebuilt alternator! Also threw in new sparks, cables, distributor cap, and rotor. The engine started WITHOUT any hesitation, and a quick drive-around showed me the engine was almost purring like a kitten.

Alternator belt tension? Thanks to Scotty, Paul, and Al! Guys you would be proud of me. I slam-dunked the belt tension as if I were an old hand. I pulled on the belt, estimated 1/4" to 1/2" (closer to

1/4"), and locked down the alternator with confidence. And yes, it is no longer the high-tensile tight that I used to put on the poor thing :) Same thing with the water-pump/power-steering belt. No problem.

You can see some pictures of this effort here at KodakGallery (free, no charge. Just click on View Slideshow).

formatting link

Two new questions:

  1. My Google search failed to turn up any good articles on cleaning and re-gapping spark plugs. Anybody can point me, a beginner, to such an article? Please see a new thread of mine on spark plugs.

  1. Also, in a new thread, how to polish oxidized aluminum block? See last picture in a series of eight in the KodakGallery/Old Ofoto link above.

Thank you,

Chris

Reply to
Chris

Congratulations. A lot of work but it looks like success. One word of caution, it appears that you did not disconnect the battery when you did the alternator work. As a safety feature, always disconnect one terminal of the battery before doing major motor work or any type of electrical work. It is a very expensive mistake to accidentally short out a battery to something electrically sensitive.

You may want to pick up a Chilton or Haynes manual for your truck. It has a lot of general how to information and even pictures of what spark plugs look like when burning properly and improperly.

What year truck do you have? Ebay usually has some great deals.

Paul.

Reply to
Paul.

Hi Paul,

Thank you for the battery warning. But being an amateur, I read up on the 22RE engine from Toyota's service manual. Much of it I really do not understand. But it did say to disconnect the negative terminal of the battery before I commence. So I did that but it does not show in the pictures unfortunately. Nonetheless, I am one who learns only by repetition, so your caveat is very welcome. Thanks.

My truck is 1992.

Chris

Reply to
Chris

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.