140 Amp Alternator

[turbo39151]

I finally broke down and bought a 140 amp alternator (for a 95/96 SS Impala) after my stocker took a crap. I upgraded all of the wiring 2 and 4 gauge leads. I reused my original belt as it's in good condition. The install was easy and everything fits like the original. However, I'm not getting the proper charge.

I have a brand new battery, everything is properly connected and I am only seeing 11.7, 11.9, 12.1 in intermittent sequences. I did see a 14.4 and even a 13. 8 for a brief instant but then it went away and dropped back down to the high 11's.

I don't even have a radio to cause such a drain!

Anyway, I checked the belt and it feels kinda loose to me. If the tensioner is already pre-set, how does one increase the tension? Is there a different belt that I'm supposed to be using?

If anyone has any info, please advise.... If a different belt is necessary please include part number if you have it.

Thanks.

 

[TurboDave]

Where are you taking those measurements and under what conditions?

 

[turbo39151]

I was using the scanmaster and the new VDO volt gauge.

I think I found the problem. The new alt has a slightly smaller pulley than the stock one...

 

[Royal-T-Ltd]

Yeah you probably need a slightly shorter belt. I know on my 200amp alternator I need a belt that is 1-1/2 or 2" shorter than stock.

 

[MIKES86GN]

royal-t-ltd......you wouldn't happen to have a part# of the belt your using with the 200 amp?????
You would be saving me a headache if you do....thx mike..

 

[CTX-SLPR]

Did you make your 200 amp using the www.turbobuicks.com kit out of a B-body alt?

 

[Royal-T-Ltd]

royal-t-ltd......you wouldn't happen to have a part# of the belt your using with the 200 amp?????
You would be saving me a headache if you do....thx mike..

No i sure dont.... but belts are just measured by length. So find out the length of stock belt [ at the parts store] and buy a belt maybe an inch shorter. Shouldnt be too hard . If you want just buy a couple of different sizes and use the one that fits best. Its pretty easy to switch belts just takes a couple of minutes.


and CTX-SLPR.... no i had my alternator converted about 4-5 years ago by a local alteernator rebuilding shop.

 

[TurboDave]

I was using the scanmaster and the new VDO volt gauge.

I think I found the problem. The new alt has a slightly smaller pulley than the stock one...

Keep a couple things in mind. First, the voltage that is displayed by Scanmaster isn't going to be terribly accurate, and the reason for that is, it has already traveled through a good bit of high reisistance wire and connections just to get to the computer(ECM), once there the ECM converts what it's seeing to a digital word that is sent out on the ALDL data stream.

Also, VDO gauges are known to be notoriously inaccurate and especially vulnerable to small changes in voltage. They have no internal reculation like many other gauge types.

The best place to check your alternator's performance is at the alternator's output post and again at the battery post with a voltmeter. You should see approx. 14.5-14.7 volts at the alternator with the engine idling, and there should be very little difference (loss) at the battery terminal.

 

[turbo39151]

I checked the numbers at the battery and at the output post.

They were 12.4-12.7.

The battery is brand new.
The alt is a new 140 amp from a 95/95 Impala.
The starter and ground wires are 2 gauge.
The alt wire is 4 gauge.

I did change the pulley off of the Impala Alt and swapped it for the OE GN one so that the stock belt would work- which conversely fixed the problem with my power steering (belt was loose).

I also have an inline battery cut-off switch. (shouldn't affect anything)

It has been suggested that I should have kept the Impala pulley on the alt and gone with a shorter belt because the larger pulley might be causing the problem.

Any ideas???

 

[TurboDave]

If you only measured 12.4-12.7 with the car running, then the alternator has to be the problem. It's not charging at all. You're reading battery voltage.
The size of the pulley wouldn't make that much of a difference. There should be at least 14 volts with the car idling.

 

[turbo39151]

Wtf?!?!??!?!!

I thought that the pulley would have been the problem (rpm's being an issue), so I swapped the original pulley back on to the impala alt and bought a new "smaller" belt. (63 5/8"). It fit's perfect! I retested the voltage at the battery and at the alt and all I get is 12.25 fairly consistently and even under load when I gave it throttle and raised the the RPM's to 2k +...

The alternator I bought was brand new. It even has the test result "dyno" sheet in the box. Will this not indicate that the alt is good from the factory? The guy at Napa is getting tired of seeing me...

Is there anything else I can do before returning the unit? Will a bench test reveal that the unit is defective?

Please advise....

 

[turbo39151]

I took the unit back to Napa and had it tested. It was BAD!

I'll ty again on Tuesday when the replacement arrives.

 

[suicide six]

how many times has this ever happened to us before,or the part fails shortly after installation.Keep all receipts,chances are youre going to need it.

 

[turbo39151]

I keep receipts for everything. I had a friend whose alternator went bad regularly on his lumina van. He had bought the unit at Discount Auto in FL and literally changed that unit 10-15 times. By the time he dumped the van he could do a swap in under 5 minutes!

I'm getting pretty good at working with the Gn alt now that I'm thinking about it...

 

[turbo39151]

Ok this is now the second Alt. Napa employees claim to have tested the unit to put out 13.5v on the bench. I took it home and installed it and I get nothing!!! Battery tests at 12.6-12.7 and at alt, it tested about the same.

WTF??? I checked and re-checked every connection. Everything is connected properly, car runs nice (on battery power only).

The folks at Napa have re-ordered a similar unit (different brand) so that I may try this dance again tomorrow!

Can anyone shed some light as to why this freakin' alternator will not cooperate with me? Can I really get two in a row that are bad?

I want to throw something

 

[scot w.]

Yes it's very possible! the units at napa are sometimes re-manufactured. I would recomend a powermaster alt and make sure that it's a brand new one! not a re-manuf. one. scot w.

 

[David65]

light

I don't see you mentioning it but, does the dash light come on when you turn the key on and not start the engine? That circuit has to be there so the alt will charge. The dash light socket connection to the back of the cluster is a known issue on some cars. You did some rewiring? Did you mess with the brown (I think) wire that goes to the lamp (L) terminal on the rear of the alt? That wire goes to the dash light, other side of the light then to 12V. Check the circuit by removing the plug from the back of the alt and grounding the brown wire. Does the dash light come on with key on? Don't put 12V directly to the L terminal on the alt. There has to be some resistance between it and 12V.

David

 

[jhanson1750]

Not sure if this will help but as David65 says the single wire that plugs into the alt is known as an "exiter" this wire creates the field so that as the rotor on the alt spins it will create a flow of electrons. I would think that new of an alt would be internially regulated but you may also have them verify the diode pack is not burnt. By the way the old "pull the positive off the battery if it runs the alt is ok" will cause a spike that will USUALLY not always burn half of the diode pack and lead to more problems down the road. Just my $0.02 :smile:

 

[turbo39151]

I have a brown wire with a plug that plugs to the back of the alt. It is spliced with a volt booster.

The other wires I have are on the output post. They are:
1. New 4 gauge to Battery
2. Howwire to fuel pump
3. Other wire that was on there before... ( have to track down and see where it goes)

I have not checked the bulb in the dash but I suppose I should.

Are you saying that if the bulb is bad the alt will not charge??

 

[David65]

I think the twist socket the bulb is in has a built-in resistor so if the bulb blows, there will still be a connection for the alt to work. But the problem might be where the socket screws into the cluster, that flexible pc board crap gets old, tarnished, brittle, cracks, etc. Test by grounding the brown wire at the alt with key on. Bulb lights, circuit ok. Check to see if the brown wire is indeed going to the L terminal, not one of the other 3. Also, till you get things ironed out, might want to disconnect the volt booster thing so as to rule it out.